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" 5 & ™ TT ttt cae = | OCT , ng by Ng LY yistom % i nee + it Tt Pian dg THE ORIGIN AND EVOLUGIONYVOP EEE E ON THE THEORY (OF ACTION REACTION AND INTERACTION OF ENERGY HALE LECTURES’ OF THE NATIONAL ACADEMY OF SCIENCES, WASHINGTON, APRIL, 1916 BY THE SAME AUTHOR MEN OF THE OLD STONE AGE. Illus- trated=wSV0e. Cab ote Pee Eel oho -O0 ‘““The book is the ripe fruit of the author's life study, served in a ‘popular’ form that can be en- joved by any educated reader; in another sense it is the first authoritative summary of the wonderful series of archeological discoveries made in recent years.’’—New York Times. Charles Scribner’s Sons ~se As , mal - ~ , - ony J ¥ Agi ¥ igack is. A ah OTR L eo A mAs A) eer bs ih gy Ss r - Tyrannosaurus rex, THE KING OF THE TYRANT SAURIANS. The climax among carnivorous reptiles of a complex mechanism for the capture, storage, and release of energy. Contemporary with and de- stroyer of the large herbivorous dinosaurs. Compare p. 224. ie | wienanca raarrsson or sooteor, cycle Subedsiueie PR PALEONTOLOGISE U. S. GEOMIGICAL BURY. CeMATOR PMPTITIN OF ait Le ‘A Rial an ee + ‘o> : my a : ; es > . we ; Je ot Eag ty tapas oe cafe ent : ; ns ie > i c os , wT ep rm he aa ? het, 2 47 ‘ im ne se: On he ey ure 7 , Co. Contemporary of a complex phies of energy. 13 dincsacirs. BR) re of | Eezs : , Pes — oe 2 - “<= f Re. =a _ $ ¢ cag 4 P . “1 ; wee ; > =& : } < > = na 5 ; = ~ 7 . ik % , _ i ' 4 Ee = t - = A NAGEL ENG EE ER OE NR FO ARTI PRMMMR Eee RS eB temas FS ae me worse Mele Ad -* ee ee “ s ns mn in ie Kn OCT 2U 1917 4 q {Be oeicar seu THE ORIGIN AND EVOLUTION OF LIFE ON THE THEORY OF ACTION REACTION AND INTERACTION OF ENERGY BY vw HENRY FAIRFIELD OSBORN SC.D. PRINCETON, HON. LL.D. TRINITY, PRINCETON, COLUMBIA, HON. D.SC. CAMBRIDGE HON. PH.D. CHRISTIANIA RESEARCH PROFESSOR OF ZOOLOGY, COLUMBIA UNIVERSITY VERTEBRATE PALZONTOLOGIST U. S. GEOLOGICAL SURVEY, CURATOR EMERITUS OF VERTEBRATE PALZONTOLOGY IN THE AMERICAN MUSEUM OF NATURAL HISTORY AUTHOR OF ‘“‘FROM THE GREEKS TO DARWIN” “THE AGE OF MAMMALS,” “‘MEN OF THE OLD STONE AGE WITH 136 ILLUSTRATIONS NEW YORK CHARLES SCRIBNER’S SONS IQI7 COPYRIGHT, 1916, BY THE SCIENCE PRESS COPYRIGHT, 1917, BY CHARLES SCRIBNER’S SONS Published September, 1917 DEDICATED TO MY COLLEAGUE AND FRIEND GEORGE ELLERY HALE HEAD OF THE MOUNT WILSON OBSERVATORY OF THE CARNEGIE INSTITUTION; ARDENT ADVOCATE OF THE SYNTHESIS OF THE SCIENCES IN RESEARCH alt, rye ar | oe By? ry eRe ; 2 iaerd of, ae ‘ ’ te ; = . v| “L ae 4a PF) 5 a th Ek | re : i Pv is Pe a ¢\ a iwi? «Rae at 4 Se H é , 5 'y >a ee 4 . ye . eel a = , € ee” ga ‘ee Ae s "4 \ ; 4 a) : 4 ‘) 2a we us ’ ih ' oe x hh , Pf te he ee ~ I) ae ‘ ; A ( A he . ie dee 2 see 7 & ha a! a hm Le , , a : °. "or 7 ee ae pee, >: «ed om hat - tf, . “®, 1 Tra © fi >) pe ; ' = ‘ 4 ’ ea MN ne a ee ie Kher te OLY es Pehl ae Gree v ai) Lay ‘ lie ae SAS? a eh 4 . We ot hey a Aas 7 iy . : - aD iy n : Vay hs J i > vent Mi My i: ( ‘ if ii by? 7] ‘ { y s LJ * 4 \ L) ' J ‘ & ‘ Pires ; \ gal? i Aa : } ; - ' 4 ‘ vue - { , e ‘ it ele \O (nea ’ ~ a iB? J ’ 7 i wr wnay . ; bet Ca eee ‘ f 3 * 4) i] ve ‘a ah ge ey tt 7 j ‘ 7 - igs - L Ans hwy) Ba) i iste Qe Me Sea. + oe Pk ae nm : Res Cool Va Oe ee | . al a oe PREFACE IN these lectures we may take some of the initial steps toward an energy conception of Evolution and an energy conception of Heredity and away from the matter and form conceptions which have prevailed for over a century. The first half of this volume is therefore devoted to what we know of the capture, storage, release, and reproduction of energy in its simplest and most elementary living phases; the second half is devoted to the evolution of matter and form in plants and animals, also interpreted largely in terms of energy and mechanics. Lest the reader imagine that through the energy conception I am at present even pretend- ing to offer an explanation of the miracles of adaptation and of heredity, some of these miracles are recited in the second part of this volume to show that the germ evolution is the most incomprehensible phenomenon which has yet been dis- covered in the universe, for the greater part of what we see in animal and plant forms is only the visible expression of the in- visible evolution of the heredity-germ. We are not ready for a clearly developed energy conception of the origin of life, still less of evolution and of heredity; yet we believe our theory of the actions, reactions, and interactions of living energy will prove! to be a step in the right direction. It is true that in the organism itself, apart from the heredity-germ, we have made great advances? in the energy 1Some of the reasons for this assertion are presented in the successive chapters of this volume and summarized in the Conclusion. 2 One of the most influential works in this direction is Jacques Loeb’s Dynamics of Living Matter, a synthesis of many years of physicochemical research on the actions and reactions of living organisms. See also Loeb’s more recent work, The Organism as a Whole, published since these lectures were written. Vii vill PREFACE conception. We observe many of the means by which energy is stored, and some of the complicated methods by which it is captured, protected, and released. We shall see that highly evolved organisms, such as the large reptiles and mammals and man, present to the eye of the anatomist and physiologist an inconceivable complexity of energy and form; but this we may in part resolve by reading the pages of this volume back- ward, Chinese fashion, from the mammal! to the monad, in which we reach a stage of relative simplicity. Thus the or- ganism as an arena for energy and matter, as a complex of in- tricate actions, becomes in a measure conceivable. The heredity-germ, on the contrary, remains inconceivable in each of its three powers, namely, in the Organism which it produces, in the succession of germs to which it gives rise, and in its own evolution in course of time. Having now stated the main object of these lectures, I invite the reader to study the following pages with care, be- cause they review some of the past history and introduce some of the new spirit and purpose of the search for causes in the domain of energy. I begin with matters which are well known to all biologists and proceed to matters which are somewhat more difficult to understand and more novel in purpose. In this review we need not devote any time or space to fresh arguments for the truth of evolution. The demonstra- ticn of evolution as a universal law of living nature is the great intellectual achievement of the nineteenth century. Evolution has outgrown the rank of a theory, for it has won a place in natural law beside Newton’s law of gravitation, and in one sense holds a still higher rank, because evolution is the universal master, while gravitation is one among its many ‘Man is not treated at all in this volume, the subject being reserved for the final lectures in the Hale Series. PREFACE 1X agents. Nor is the law of evolution any longer to be associ- ated with any single name, not even with that of Darwin, who was its greatest exponent.t It is natural that evolution and Darwinism should be closely connected in many minds, but we must keep clear the distinction that evolution is a law, while Darwinism is merely one of the several ways of inter- preting the workings of this law. In contrast to the unity of opinion on the Jaw of evolution is the wide diversity of opinion on the causes of evolution. In fact, the causes of the evolution of life are as mysterious as the law of evolution is certain. Some contend that we already know the chief causes of evolution, others contend that we know little or nothing of them. In this open court of con- jecture, of hypothesis, of more or less heated controversy, the great names of Lamarck, of Darwin, of Weismann figure promi- nently as leaders of different schools of opinion; while there are others, like myself,? who for various reasons belong to no school, and are as agnostic about Lamarckism as they are about Darwinism or Weismannism, or the more recent form of Darwinism, termed Mutation by de Vries. In truth, from the period of the earliest stages of Greek thought man has been eager to discover some natural cause of evolution, and to abandon the idea of supernatural interven- tion in the order of nature. Between the appearance of The Origin of Species, in 1859, and the present time there have been great waves of faith in one explanation and then in an- other: each of these waves of confidence has ended in disap- pointment, until finally we have reached a stage of very general 1See From the Greeks to Darwin (Macmillan & Co., 1894), by the present author, in which the whole history of the evolution idea is traced from its first conception down to the time of Darwin. 2 Osborn, H. F., ‘‘The Hereditary Mechanism and the Search for the Unknown Factors of Evolution,’ The Amer. Naturalist, May, 1895, pp. 418-4309. x PREFACE scepticism. Thus the long period of observation, experiment, and reasoning which began with the French natural philosopher Buffon, one hundred and fifty years ago, ends in 1916 with the general feeling that our search for causes, far from being near completion, has only just begun. Our present state of opinion is this: we know to some extent jow plants and animals and man evolve; we do not know why they evolve. We know, for example, that there has existed a more or less complete chain of beings from monad to man, that the one-toed horse had a four-toed ancestor, that man has descended from an unknown ape-like form somewhere in the Tertiary. We know not only those larger chains of descent, but many of the minute details of these transforma- tions. We do not know their internal causes, for none of the explanations which have in turn been offered during the last hundred years satisfies the demands of observation, of experi- ment, of reason. It is best frankly to acknowledge that the chief causes of the orderly evolution of the germ are still en- tirely unknown, and that our search must take an entirely fresh start. As regards the continuous adaptability and fitness of liv- ing things, we have a reasonable interpretation of the causes of some of the phenomena of adaptation, but they are the smaller part of the whole. Especially mysterious are the chief phenomena of adaptation in the germ; the marvellous and continuous fitness and beauty of form and function remain largely unaccounted for. We have no scientific explana- tion for those processes of development from within, which Bergson! has termed “‘lévolution créatrice,’ and for which Driesch? has abandoned a natural explanation and assumed ' Bergson, Henri, 1907, L’ Evolution Créatrice. * Driesch, Hans, 1908, The Science and Philosophy of the Organism. PREFACE x1 the existence of an entelechy, that is, an internal perfecting influence. This confession of failure is part of the essential honesty of scientific thought. We recall the fact that our baffled state of mind is by no means new, for in Kant’s work of 1790, his Methodical System of the Teleological Faculty of Judgment, he ) divides all things in nature into the “inorganic,” in which ¢ ) in which the active teleological (7. e., purposive) principle of adaptation is sup- posed to prevail. There was in Kant’s mind a cleft between the domain of primeval matter and the domain of life, for in natural causes prevail, and the “ organic,’ the latter he assumes the presence of a supernatural principle, of final causes acting toward definite ends. This view is ex- pressed in his Teleological Faculty of Judgment as follows: “But he” (the archeologist of Nature) ‘“‘must for this end ascribe to the common mother an organization ordained pur- posely with a view to the needs of all her offspring, otherwise the possibility of suitability of form in the products of the animal and vegetable kingdoms cannot be conceived at all.’”’! “Tt is quite certain that we cannot become sufficiently acquainted with organized creatures and their hidden poten- tialities by aid of purely mechanical natural principles; much less can we explain them; and this is so certain, that we may boldly assert that it is absurd for man even to conceive such an idea, or to hope that a Newton may one day arise able to make the production of a blade of grass comprehensible, ac- cording to natural laws ordained by no intention; such an insight we must absolutely deny to man.’’? For a long period after The Origin of Species appeared, Haeckel and many others believed that Darwin had arisen as the Newton for whom Kant did not dare to hope; but no 1 Kant, Emmanuel, 1790, § 70. 2 Tbid., § 74. Xl PREFACE one now claims for Darwin’s law of natural selection a rank equal to that of Newton’s law of gravitation. If we admit the possibility that Kant was right, and that we can never become sufficiently acquainted with organized creatures and their hidden potentialities by aid of purely natural principles, we may be compelled to regard the origin and evolution of life as an ultimate law like the law of gravita- tion, which may be mathematically and physically defined, but cannot be resolved into any causes. We are not willing, however, to make such an admission at the present time and to abandon the search for causes. The question then arises, why has our long and arduous search after the causes of evolution so far been unsuccessful ? One reason why our search may have failed appears to be that the chief explorers have been trained in one school of thought, namely, the school of the naturalist. They all began their studies with observations on the external form and color of animals and plants; they have all observed the end results of long processes of evolution. Buffon derived his ideas of the causes of evolution from the comparison of the wild and domestic animals of the Old and New Worlds; Goethe observed the com- parative anatomy of man and of the higher animals; Lamarck observed the higher phases of the vertebrate and invertebrate animals; Darwin observed the form of most of the domestic animals and cultivated plants and, finally, of man, and noted the adaptive significance of the colors of flowers and birds, and the relations of flowers with birds and insects; de Vries compared the wild and cultivated species of plants. Thus all the great naturalists in turn—Buffon, Goethe, Lamarck, Dar- win, and de Vries—have attempted to reason backward, as it were, from the highly organized appearances of form and color to their causes. The same is true of the paleontologists: PREFACE xl Cope turned from the form of the teeth and skeleton backward to considerations of cause and energy, Osborn! reached a con- ception of evolution as of the relations of fourfold form, and hence proposed the word tetraplasy. The Heredity theories of Darwin, of de Vries, of Weis- mann have also been largely in the material conceptions of fine particles of matter such as “‘pangens”’ and “‘determinants.”’ There has been some consideration of function and of the internal phenomena of organisms, but there has been little or no serious attempt to reverse the mental processes of the naturalist and substitute those of the physicist in considering the causes of evolution.’ Moreover, all the explanations of evolution which have been offered by three generations of naturalists align themselves under two main ideas only. ‘The first is the idea that the causes of evolution are chiefly from without inward, namely, beginning in the environment of the body and extending into the germ: this idea is centripetal. ‘The second idea is just the reverse: it is centrifugal, namely, that the causes begin in the germ and extend outward into the body and into the environ- ment. The pioneer of the first order of ideas is Buffon, who early reached the opinion that favorable or unfavorable changes of environment directly alter the hereditary form of succeed- ing generations. Lamarck,* the founder of a broader and more modern conception of evolution, concluded that the changes of form and function in the body and nervous system induced by habit and environment accumulate in the germ, 1 Osborn, H. F., ‘‘Tetraplasy, the Law of the Four Inseparable Factors of Evolution,” Jour. Acad. Nat. Sci. Phila., special anniversary volume issued September 14, 1912, pp. 275-309. 2 See fuller exposition on pp. 10-23 of this volume. 3 For a fuller exposition of the theory of Lamarck, see pp. 143, 144. shi PREFACE and are handed on by heredity to succeeding generations. This essential idea of LaMARCKISM was refined and extended by Herbert Spencer, by Darwin himself, by Cope and many others; but it has thus far failed of the crucial test of observa- tion and experiment, and has far fewer adherents to-day than it had forty years ago. We now perceive that Darwin’s original thought turned to the opposite idea, namely, to sudden changes in the heredity- germ itself! as giving rise spontaneously to more or less adap- tive changes of body form and function which, if favorable to survival, might be preserved and accumulated through natural selection. This pure DARWINISM has been refined and extended by Wallace, Weismann, and especially of late by de Vries, whose ‘“‘mutation theory” is pure Darwinism in a new guise. Weismann’s great contribution to thought has been to point out the very sharp distinction which undoubtedly exists between the hereditary forces and predispositions in the hered- ity-germ and the visible expression of these forces in the or- ’ as Weismann terms it— ganism. It is in the “germ-plasm,’ in this volume termed the “ heredity-chromatin’’—that the real evolution of all predispositions to form and function is taking place, and the problem of causes of evolution has become an infinitely more difficult one since Weismann has compelled us to realize that the essential question is the causes of germinal evolution rather than the causes of bodily evolution or of en- vironmental evolution. Again, despite the powerful advocacy of pure Darwinism by Weismann and de Vries in the new turn that has been given to our search for causes by the rediscovery of the law of Mendel and the heredity doctrines which group under MEN- 1 Osborn, H. F., “Darwin’s Theory of Evolution by the Selection of Minor Saltations,”’ The Amer. Naturalist, February, 1912, pp. 76-82. PREFACE XV DELISM,! it may be said that Darwin’s law of selection as a natural explanation of the origin of a// fitness in form and func- tion has also lost its prestige at the present time, and all of Darwinism which now meets with universal acceptance is the law of the survival of the fittest, a limited application of Darwin’s great idea as expressed by Herbert Spencer. Few biologists to-day question the simple principle that the fittest tend to survive, that the unfit tend to be eliminated, and that the present aspect of the entire living world is due to this great pruning-knife which is constantly sparing those which are best fitted or adapted to any conditions of environment and cutting out those which are less adaptive. But as Cope pointed out, the survival of fitness and the origin of fitness are two very different phenomena. If the naturalists have failed to make progress in the search for causes, I believe it is chiefly because they have attempted to reason backward from highly complex plant and animal forms to causes. The cart has always been placed before the horse; or, to express it in another way, thought has turned from the forms of living matter toward a problem which involves the phenomena of living energy; or, still more briefly, we have been thinking from matter backward into energy rather than from energy forward into matter and form. All speculation on the origin of life, fruitless as it may at first appear, has the advantage that it compels a sudden re- versal of the naturalist’s point of view, for we are forced to work from energy upward into form, because, at the begin- ning, form is nothing, energy is everything. Energy appears to be the chief end of life—the first efforts of life work toward the capture of energy, the storage of energy, the release of 1 Mendelism chiefly refers to the distinction and laws of distribution of separable or unit characters in the germ and in the individual in course of its development. Xvl1 PREFACE energy. The earliest adaptations we know of are designed for the capture and storage of energy. Matter in the state of relative rest known as plant and animal form is present, but, in the simplest and lowliest types of life, form does not conceal and mask the processes of energy as it does in the higher types. Similarly, the earliest fitness we discover in the bacteria or monads is the fitness of group- ing and organizing different kinds of energy—the energy of molecules, of atoms, of electrons as displayed in the twenty- six or more chemical elements which enter into life. In searching among these early episodes of life in its origin we discover that four complexes of energy are successively added and combined. The Inorganic Environment of the sun, of the earth, of the water, of the atmosphere is exploited thor- oughly in search of energy by the Organism: the organism itself becomes an organism only by utilizing the energy of the environment and by coordinating its own internal energies. Whether the Germ as the special centre of heredity and repro- duction of energy is as ancient as the organism we do not know; but we do know that it becomes a distinct and highly complex centre of potential energy which directs the way to the entire energy complex of the newly developing organism. Finally, as organisms multiply and acquire various kinds of energy, the Life Environment arises as a new factor in the energy complex. Thus in the process of the origin and early evolution of life, complexes of four greater and lesser energy groups arise, namely: INORGANIC ENVIRONMENT: the energy content in the sun, the earth, the water, and the air; ORGANISM: the energy of the individual, developing and changing the cells and tissues of the body, including that part of the germ which enters every cell; HEREDITY-GERM: the energies of the heredity substance (heredity-chromatin) concentrated in the reproduc- PREFACE XVll tive cells of continuous and successive generations, as well as in all the cells and tissues of the organism; and LIFE ENVIRON- MENT: beginning with the monads and alge and ascending in a developing scale of plants and animals. There are here four evolutions of energy rather than one, and the problem of causes is how the four evolutions are ad- justed to each other; and especially how the evolution of the germ adjusts itself to that of the inorganic environment and of the life environment, and to the temporary evolution of the organism itself. I do not propose to evade the difficulties of the problem of the origin and evolution of life by minimizing any of them. Whether our approach through energy will lead to the dis- covery of some at least of the unknown causes of evolution remains to be determined by many years of observation and experiment. Whereas our increasing knowledge of energy in matter reveals an infinity of energized particles even in the in- finitely minute aggregations known as molecules—an infinity which we observe but do not comprehend—we find in our search for causes of the origin and evolution of life that we have reached an entirely new point of departure, namely, that of the physicist and chemist rather than the old point of departure of the naturalist. We have obtained a starting-point for new and untried paths of exploration which may be followed dur- ing the present century—paths which have long been trodden with a different purpose by physicists and chemists, and by physiologists and biochemists in the study of the organism it- self. The reader may thus follow, step by step, my own experi- ence and development of thought in preparing these lectures. The reason why I happened to begin this volume with the prob- XVlil PREFACE lem of energy and end with that of the evolution of form is that these lectures were prepared and delivered midway in a cosmic-evolution series which opened with Sir Ernest Ruther- ford’s! discourse on ‘‘The Constitution of Matter and the Evolution of the Elements,’ and continued with ‘The Evolu- tion of the Stars and the Formation of the Earth,” by Doctor William Wallace Campbell,? and “‘ The Evolution of the Earth,” by Professor Thomas Chrowder Chamberlin.? My friend George Ellery Hale placed upon me the responsibility of weaving the partly known and still more largely unknown narrative which connects the forms of energy and matter ob- served in the sun and stars with the forms of energy and matter which we observe in the bodies of our own mammalian ances- tors. Certainly we appear to inherit some, if not all, of our physicochemical characters from the sun; and to this degree we may claim kinship with the stellar universe. Some of our distinctive characters and functions are actually properties of our ancestral star. Physically and chemically we are the off- spring of our great luminary, which certainly contributes to us all our chemical elements and all the physical properties which bind them together. Some day a constellation of genius will unite in one labora- tory on the life problem. This not being possible at present, I have endeavored during the past two years‘ for the purposes ‘Rutherford, Sir Ernest, “‘The Constitution of Matter and the Evolution of the Klements,”’ first series of lectures on the William Ellery Hale foundation, delivered in April, 1914; Pop. Sci. Mon., August, 1915, pp. 105-142. * Campbell, William Wallace, “‘The Evolution of the Stars and the Formation of the Earth,” second series of lectures on the William Ellery Hale foundation, delivered De- cember 7 and 8, 1914; Pop. Sci. Mon., September, 1915, pp. 209-235; Scientific Monthly, October, 1915, pp. 1-17; November, 1915, pp. 177-194; December, 1015, pp. 238-255. ® Chamberlin, Thomas Chrowder, ‘‘The Evolution of the Earth,’’ third series of lec- tures on the William Ellery Hale foundation, delivered April 19-21, 1915; Scientific Monthly, May, 1916, pp. 417-437; June, 1916, pp. 536-556. ‘I first opened a note-book on this subject in the month of April, t915, when I was invited by Doctor George Ellery Hale to undertake the preparation of these lectures. PREFACE X1x of my own task to draw a large number of specialists together in correspondence and in a series of personal conferences and discussions; and whatever merits this volume may possess are partly due to their generous response in time and thought to my invitation. Their suggestions are duly acknowledged in footnotes throughout the text. I have myself approached the problem through a synthesis of astronomy, geology, physics, chemistry, and biology. In consulting authorities on this subject I have made one exception, namely, the problem of the origin of life itself with its vast literature going back to the ancients—I have read none of it and quoted none of it. In order to consider the problem from a fresh and unbiassed point of view, I have also purposely refrained from reading any of the recent and authoritative treatises of Schadfer,! Moore,? and others on the origin of life. It will be interesting for the reader to compare the conclusions previously reached by these distinguished chemists with those presented in the following pages. For invaluable guidance in the phenomena of physics I am deeply indebted to my colleague Professor Michael I. Pupin, of Columbia University, who has given me his views as to the fundamental relation of Newton’s laws of motion to the modern laws of heat and energy (thermodynamics), and has clarified the laws of action, reaction, and interaction from the physical standpoint. Without this aid I could never have developed what I believe to be the new biological principle set forth in this work. I owe to him the confirmation of the use of the word interaction as a physical term, which had occurred to me first as a biological term. 1 Schafer, Sir Edward A., Life, Its Nature, Origin, and Maintenance, Longmans, Green & Co., New York, 1912. * Moore, Benjamin, The Origin and Nature of Life, Henry Holt & Co., New York; Williams & Norgate, London, 1913. 0.8 PREFACE As to the physicochemical actions and reactions of the living organism I have drawn especially from Loeb’s Dynamics of Living Matter. In the physicochemical section I am also greatly indebted to the very suggestive work of Henderson entitled The Fitness of the Environment, from which I have especially derived the notion that fitness long antedates the origin of life. Professor Hans Zinsser, of Columbia University, has aided in a review of Ehrlich’s theory of antibodies and the results of later research concerning them. Professor Ulric Dahlgren, of Princeton University, has aided the preparation of this work with valuable notes and suggestions on the light, heat, and chemical rays of the sun, and on phosphorescence and electric phenomena in the higher organisms. In the geochemical and geophysical section I am indebted to my colleagues in the National Academy, F. W. Clarke and George F. Becker, not only for the revision of parts of the text, but for many valuable suggestions and criticisms. For suggestions as to the chemical conditions which may have prevailed in the earth during the earliest period in the origin of life, as well as for criticisms and careful revision of the chemical text I am especially indebted to my colleague in Columbia University, Professor William J. Gies. In the astronomic section I desire to express my indebted- ness to George Ellery Hale, of the Mount Wilson Observatory, for the use of photographs, and to Henry Norris Russell, of Princeton University, for notes upon the heat of the primordial earth’s surface. In the early narrative of the earth’s history and in the subsequent geographic and physiographic charts and maps Professor Charles Schuchert and Professor Joseph Barrell, of Yale University, kindly cooperated with the loan of illustrations and otherwise. In the section on the evolution of bacteria, which is a part pertaining to the idea of the early PREFACE XX1 evolution of energy in living matter, I enjoyed the cooperation of Doctor I. J. Kligler, formerly of the American Museum of Natural History, and now at the Rockefeller Institute for Medical Research. | In the botanical section I am especially indebted to Pro- fessor T. H. Goodspeed, of the University of California, and to Doctor Marshall Avery Howe, of the Botanical Gardens, for many valuable notes and suggestions, as well as for certain illustrations. In the early zoological section I am indebted to my colleagues at Columbia University, Professor Edmund B. Wilson and Professor Gary N. Calkins. Especial thanks are due to Mr. Roy W. Miner, of the American Museum, for his careful comparisons of recent forms of marine life with the Cam- brian forms discovered by Doctor Charles Walcott, who sup- plied me with the beautiful photographs shown in Chapter IV. In preparing the chapters on the evolution of the verte- brates, I have turned to my colleague Professor W. K. Gregory, of the American Museum and Columbia University, who has aided both with notes and suggestions, and in the supervision of various illustrations relating to the evolution of vertebrate form. The illustrations are chiefly from the collections of the American Museum of Natural History, as portrayed in original drawings by Charles R. Knight, Erwin S. Christman, and ' Richard Deckert. The entire work has been faithfully collated and put through the press by my research assistant, Miss Christina D. Matthew. It affords me great pleasure to dedicate this work to the astronomer friend whose enthusiasm for my own field of work in biology and paleontology has always been a source of en- couragement and inspiration. HENRY FAIRFIELD OSBORN. AMERICAN MusEuM OF NATURAL HIsTory, February 26, 1917. os ny ghee Las CONTENTS INTRODUCTION PAGE OME BOIS TIONSBREGARDING-LIFEN ct AE nett) Shae (eee a, I MREP RENE VEeCONCE PDO RIT LIFE, Sool. rt i Se, ee eh eee She ies 10 cate COMPLEXTS OFS ENERGY Wot) fae ele tee 18 PA i a AOA PTATION SOR WENER GY GEUAE DE Rea PREPARATION OF THE EARTH FOR LIFE ee emi RECA RTH: tse es itn Aire ast hy cae tet Se eee 24 AR CR SC WY T Ree Slt eS octy ce th! AWN Gy pas Bee Cakes NES ii eM OSDH ER Eis pier irc: wiser er SES eee eh ee Be my BO CHAPTER If THE SUN AND THE PHYSICOCHEMICAL ORIGINS OF LIFE om bic CAN S8h eT 2 eile A ae a Pr Re eee Ga en nne et ay be} Pier MEN toa iN: THE YSUN 3/25 2. GAT Aah Sled Ie. cae Leys Bee eed 5 MA Me DRELEATRIC™IONERGY, ei8,icr i. ofl, kee. LS Gh ees NL Re AS PGR Ee APPR (SUN Msi Mune Fathi aah igs! SA Pa ap een a OT LONIZATION- tHE ELEGLRICCENERGVaOF ATOMS i G5) agus BA oe) toe, 53 COORDINATION OF ACTIVITIES BY MEANS OF INTERACTION... 50 PaNGTioNS cOn ete CHEMICAL, LIFE ELEMENTS. 7603.7; (.0 Ge Peep te 2 ESO ise cet A eee eee Orth ah ee Pia Sr ht teed), ee ge ne Xxill XX1V CONTENTS NEW ORGANIC COMPOUNDS . INTERACTIONS—ENZYMES, ANTIBODIES, HORMONES, AND CHALONES CHEMICAL MESSENGERS . PHYSICOCHEMICAL DIFFERENTIATION CHAPTER] fil ENERGY EVOLUTION OF BACTERIA, ALG#, AND PLANTS EVOLUTION OF BACTERIA PROTOPLASM AND HEREDITY-CHROMATIN . CHLOROPHYLL—THE SUNLIGHT CONVERTER OF PLANTS EVOLUTION OF ALG4—THE MOST PRIMITIVE PLANTS PLANT AND ANIMAL EVOLUTION CONTRASTED PART II. .THE EVOLUTION OF ANIMAL FORM CHAPTER IV THE ORIGINS OF ANIMAL LIFE AND EVOLUTION OF THE INVERTEBRATES EVOLUEION OF (PROTOZORiE athe aan aie en EVOBUTIONZOR NER FAZOR igor twee os a ie, eee ee CAMBRTAN INVEREEBRATES@ fume 4 ath Atle ae ee ENVIRONMENTA LyCHANUCES amend) lly meanness NOSTATIONS (OR WAAGEN | i etcpecs oe ame eee ee GHABTERSV VISIBLE AND INVISIBLE EVOLUTION OF THE EVOLUTION OF THE GERM CHARACTER EVOLUTION . THE LAWS OF ADAPTATION VERTEBRATES PAGE 80 QI 99 IOI 105 IIO 117 118 134 138 I4I 146 152 CONTENTS | XXV CHAPTER VI EVOLUTION OF Bopy ForM IN THE FISHES AND AMPHIBIANS PAGE HARTI ES LURNO WN EISH EO, Sue nee Uucilthe Ses Mc MeON mph mip Weer st MM emurtyCS BREN CAR MOREDARISHEG, Wisi caret Many eee aL iver) 2 Lar Se ae eet Oe PRIMORDIAL SHARKS ROIS os NEL iia We a ote oa ENY the lala de ty ll ABEL eRe ty EL NT Eto PeMODERNANISHES -cnty Qh Simon th ie tates Tees Pee) a Oe TOG BV ARLLON ROW, TH FeAMPHIBLANG jt. ir0 es. SAN aE MPa aig Me ee Te CHAPTER VII ForM EVOLUTION OF THE REPTILES AND BIRDS PEE STM RE TILES ee ees? Lk ek ce Ce De Mi Ie emai aT SP DAMA eCiR eR P TL LIS ele gem Sich. MUR owe ba mmiieny Ve Uh ae ME aaa rT PDAS tLVERRADIATION, OF REPTILES ¢ ta 00s 2 Mata Matiewy me uae Piru. TiVo Bree LC with DM PETS area ate ics tole, i oe lesa ay wn Wl RM Mth thy ia CU A ARNEVOR GUSMDINOSATIR SG key ito by do lucer’ beast Ril 0 2 TMS eee ROOT C) PR BL ViER US eDINOSA URS A.) iny pitts i Phen) | aaemrageen Coot EN ead aT Te CORRE LID Roe seit epeh ie. Sei. oo he pn RON Rae soc oe tah Se OO) EI CTINMOP EE LR DSC mn, Wr yer ca arte AU whe on Os Le vt | a ame ag 2G PBR TUDEREPTIUIANS EVOLUTION (ct co ota aaa heey loo ben. tun oT CHAPTER RV HI EVOLUTION OF THE MAMMALS PU rE A TAMA Thalia e305 00 Ne MAE NR bee Tigers Oe ee OL Ue OS A EAR LOCTRRREVOUTION (CMT bu Hole) ys yt IR Stay ap ts Un a 2 eM aN BO oy PES SOMME VOTUTION Met ass vig awl sth Ngee hanes!” or driven by the pressure of light (Arrhenius).6 The fact that so far as we know life on the earth has only originated once or during one period, and not repeatedly, does not appear to favor these hypotheses; nor is it courageous to put off the problem of life origin into cosmic 1 Jordan, Edwin O., 1908, pp. 67, 68. 2O%. cit., D. 08. 3 Loeb, Jacques, 1906, p. 1006. * Cultures of bacteria have even been exposed to the temperature of liquid hydrogen (about —250° C.) without destroying their vitality or sensibly impairing their biologic qualities. This temperature is far below that at which any chemical reaction is known to take place, and is only about 23 degrees above the absolute zero point at which, it is believed, molecular movement ceases. On the other hand, when bacteria are frozen in water during the formation of natural ice the death rate is high. See Jordan, Edwin O., 1908, p. 60. 5 Poulton, Edward B., 1896, p. 818. 6 Pirsson, Louis V., and Schuchert, Charles, 1915, pp. 535, 536. 50° THE ORIGIN AND EVOLUTION OF LIFE space instead of resolutely seeking it within the forces and elements of our own humble planet. The thermal conditions of living matter point to the prob- ability that life originated at a time when portions at least DEVONIAN SILURIAN ORDOVICIAN PALAOZOIC CAMBRIAN VER KEWEENAWAN ANIMIKIAN CW HURONIAN AND \ { eer i 1 | | Ll. : ty : N Sie | \ | E= ATES ARBO ALGOMIAN ( aaa t LICA 1 1 ' Lt 1 1 1 = 1 | SUDBURIAN ' Fa < we = oO S o- @ oO +S Ze rs BACTERIA - DEPOSITING Ss N aw on a ee I 1 ! ee ae E-CELLED ANIMALS : OUD INVERTEBR \ ! \ LAURENTIAN MANY-CELLED ANIMALS,“ / —_— ee ee ae _—— -—— ee oe IRON, LIME, SULPHUR, ETC. ALGAE AND M DEPOSITING LIME SINGLE-CELLED RLANTS DEPOSITING SILICEOUS OOZE PROTOZOA, SINGL DEPOSITING LIME AND SI ca ses | eevee ho erases go 5 ~— Zz < oc m = < Oo Lu or O. EARLIEST INDICATIONS OF GRENVILLE LIVING FORMS (KEEWATIN) (COUTCHICHING) ARCH/ZOZOIC (ARCHAAN) Fic. 5. THE EARLiest PHYLA OF PLANT AND ANIMAL LIFE. Chart showing the theoretic derivation of chordates and vertebrates from some inverte- brate stock, and of the invertebrates from some of the protozoa. The diagonal lines indicate the geologic date of the earliest known fossil forms in the middle Algonkian. The earliest well-known invertebrate fauna is in the Middle Cambrian (see pp. 118-134, and Figs. 20-27). Although diatoms are among the simplest known liy- ing forms and probably represent a very early stage in the evolution of life, no fossil forms are known earlier than two species from the Lias, while all the rest date from the Cretaceous. of the earth’s surface and waters had temperatures of between 89° C. and 6° C.; and also to the possibility of the origin of life before the atmospheric vapors admitted a regular supply of sunlight. DHE SOCAL Ri Or es UNEIGH D 51 Capture of the Energy of Sunlight After the sun’s heat living matter appears to have captured the sun’s light, which is essential, directly or indirectly, to all living energy higher than that of the most primitive bacteria. The discovery by Lavoisier (1743-1794) and the development (1804) by de Saussure! of the theory of photosynthesis, namely, that sunshine combining solar heat and light is a perpetual source of living energy, laid the foundations of biochemistry and opened the way for the establishment of the law of the conservation of energy within the living organism. Thus arose the first conception of the cycle of the elements continually passing through plants and animals which was so grandly formulated by Cuvier in 1817:2. “La vie est donc un tourbillon plus ou moins rapide, plus ou moins compliqué, dont la direction est constante, et qui entraine toujours des molécules de mémes sortes, mais ot les molécules individuelles entrent et d’ot elles sortent continuellement, de maniére que la forme du corps vivant lui est plus essentielle que sa matiére.”’ CHEMICAL COMPOSITION OF CHLOROPHYLL? Carbon Hydrogen Nitrogen WD atetG he) VAs Bee FS SRR Ra ROR MRE A SoMa draw ils AAR den Phosphorus Magnesium The green coloring matter of plants is known as chloro- phyll; its chemical composition according to Hoppe-Seyler’s 1 De Saussure, N. T., 1804. 2 Cuvier, Baron Georges L. C. F. D., 1817, p. 13. 3 Sachs, Julius, 1882, p. 758. 52 THE ORIGIN AND EVOLUTION OF LIFE analysis is given here. Potassium is essential for its assimi- lating activity. Iron (often accompanied by manganese), al- though essential to the production of chlorophyll, is not con- tained in it. The chlorophyll-bearing leaves of the plant in the presence of sunlight separate oxygen atoms from the carbon and hydrogen atoms in the molecules of carbon dioxide (CO,.) and of water (H.O), storing up the energy of the hydro- gen and carbon products in the carbohydrate substances of the plant, an energy which is stored by deoxidation (separation of oxygen), and which can be released only through reoxidation (addition of oxygen). Thus the celluloses, sugars, starches, and other similar substances deposit their kinetic or stored energy in the tissues of the plant and release that energy through the addition of oxygen, the amount of oxygen required being the same as that needed to burn these substances in the air to the same degree; in brief, through a combustion which generates heat.1. Thus living matter utilizes the energy of the sun to draw a continuous stream of electric energy from the chemical elements in the earth, the water, and the atmos- phere. This was the first step in the interpretation of life processes in the terms of physics and chemistry, rather than in terms of a peculiar vitalism. What had previously been regarded as a special vital force in the life of plants thus proved to be an adaptation of physicochemical forces. The chemical action of chlorophyll is even now not fully understood, but it is known to absorb most vigorously the solar rays between B and C of the spectrum,? and these rays are most effective in the assim- ilation of energy or food by the plant. While the effect of the solar rays between D and E is minimal, those beyond F are again effective. In heliotropic movements both of plants and UW... J: Gies: 2 Loeb, Jacques, 1906, p. 115. IONIZATION 53 animals the blue rays are more effective than the red.1. Spores given off as ciliated cells from the alge seek first the blue rays. Since the food supply of animals is primarily derived from chlorophyll-bearing plants, animals are less directly dependent on the solar light and solar heat, while the chemical life of plants fluctuates throughout the day with the variations of light and temperature. Thus Richards? finds in the cacti that the breaking down of the acids through the splitting of the acid compounds is a respiratory process caused by the alternate oxidation and deoxidation of the tissues through the action of the sun. The solar energy transformed into the chemical potential energy of the compounds of carbon, hydrogen, and oxygen in the plants is transmuted by the animal into motion and heat and then dissipated. Thus in the life cycle we observe both the conservation and the degradation of energy, corresponding with the first and second laws of thermodynamics developed in physics by the researches of Newton, Helmholtz, Phillips, Kelvin, and others.? The remaining life processes correspond in many ways to Newton’s third law of motion. ACTION AND REACTION AS ADAPTIVE PROPERTIES OF THE LIFE ELEMENTS The adaptation of the chemical elements to life processes is due to their incessant action and reaction, each element having its peculiar and distinctive forms of action and reaction, which in the organism are transmuted into functions. Such activity of the life elements is largely connected with forms of electric energy which the physicists call zonization, while the correlated or coordinated interaction of various groups “OP: Gila D..127, 2 Richards, Herbert M., 1915, pp. 34, 73-75. 3’ Henderson, Lawrence J., 1913, pp. 15-18. 54 THE ORIGIN AND EVOLUTION OF LIFE of life elements is largely connected with processes which the chemists term catalysts. Ionization, the actions and reactions of all the elements and electrolytic compounds—according to the hypothesis of Arrhe- nius, first put forth in 1887—1is primarily due to electrolytic dissociation whereby the molecules of all acids (e. g., carbonic acid, H.COs), bases (e. g., sodium hydroxide, NaOH), and salts (e. g., sodium chloride, NaCl) give off streams of the electrically charged particles known as ions. Ionization is dependent on the law of Nernst that the greater the dielectric capacity of the solvent (e. g., water) the more rapid will be the dissociation of the substances dissolved in it, other conditions remaining the same. } IONIZATION OF THE ELEMENTS THUS FAR DISCOVERED IN LIVING ORGANISMS Mainly or Wholly with or in Negative Ions} Mainly or Wholly with or in Positive Ions! Non-metallic Metallic Carbon? (e. g.,4 carbonates) Silicon Hydrogen® Iron’ Lithium Oxygen? (e. g.,4 sulphates) Iodine Potassium Copper Nickel Nitrogen”. (e. g.,4 nitrates) Bromine | Sodium Aluminum | Radium Phosphorus? (ec. g.,4 phosphates) | Fluorine || Calcium Barium Strontium Sulphur? (e. g.,4 sulphates) Boron Magnesium | Cobalt Zinc Chlorine (e. g.,4 chlorides) Arsenic® | Manganese | Lead * An ion is an atom or group of atoms carrying an electric charge. The positive ions (cations) of the metallic elements move toward the cathode; the negative ions (anions) given off by the non-metallic elements move toward the anode. * Together with hydrogen conspicuous in living colloids and non-electrolytes—very little in the indicated ionized forms. * Occurs also, as NH4, in positive ions. Here the hydrogen overbalances the nitrogen. * Substances occurring in living matter. * Arsenic itself is a metal, but in living compounds it is an analogue of phosphorus and occurs in negative ions when ionized. * Pictet has obtained results indicating that liquid and solid hydrogen are metallic. Hydrogen is metallic in behavior, though non-metallic in ap pearance. ‘Tron in living compounds is chiefly non-ionized, colloidal. Apparently this is also true of copper, aluminum, barium, cobalt, lead, nickel, strontium, and zinc. As to ra- dium, however, there is no information on this point. Thus, ions are atoms or groups of atoms carrying electric charges which are positive when given off from metallic ele- IONIZATION 55 ments, and negative when given off from non-metallic elements. Electrolytic molecules, according to this theory, are constantly dissociating to form ions, and the ions are as constantly recom- bining to form molecules. Since the salts of the various min- eral elements are constantly being decomposed through elec- trolytic lonization, they play an important part in all the life phenomena; and since similar decomposition is induced by currents of electricity, indications are that all the development of living energy is in a sense electric. The ionizing electric properties of the life elements are a matter of prime importance. We observe at once in the table above that all the great structural elements which make up the bulk of plant and animal tissues are of the non-metallic group with negative ions, with the single exception of hydro- gen which has positive ions. All these elements are of low atomic weight, and several of them develop a great amount of heat in combustion, hydrogen and carbon leading in this function of the release of energy, which invariably takes place in the presence of oxygen. On the other hand, the lesser com- ponents of living compounds are the metallic elements with positive ions, such as potassium, sodium, calcium, and mag- nesium, calcium combining with carbon or with phosphorus as the great structural or skeletal builder in animals. ‘There is also so much carbonaceous protein in the animal skeleton that calcium in animals takes the place of carbon in plants only in the sense that it reduces the proportion of carbon in the skele- ton: it shares the honors with carbon. In general the electric action and reaction of the non- metallic and the metallic elements dissolved or suspended in water are now believed to be the chief phenomena of the in- ternal functions of life, for these functions are developed always in the presence of oxygen and with the energy either of the 56 THE ORIGIN AND EVOLUTION OF LIFE heat of the earth or of the sun, or of both the heat and lght Olatheesuie Finally, we observe that ionization is connected with the radioactive elements, of which thus far only radium has been detected in the organic compounds, although the others may be present. Phosphorescence in plants and animals is treated by Loeb! and others as a form of radiant energy. While developed in a number of living animals—including the typical glowworms in which the phenomenon was first investigated by Faraday—the living condition is not essential to it because phosphorescence continues after death and may be produced in animals by non-living material. Many organisms show phosphorescence at comparatively low temperatures, yet the presence of free oxygen appears to be necessary. In Rutherford’s experiments on radioactive matter? he tells us that in the phosphorescence caused by the approach of an emanation of radium to zinc sulphate the atoms throw off the alpha particles to the number of five billion each second, with velocities of 10,000 miles a second; that the alpha particles in their passage through air or other medium produce from the neutral molecules a large number of negatively charged ions, and that this ionization is readily measurable. INTERACTION OR COORDINATION OF THE PROPERTIES OF THE LIFE ELEMENTS The actions and reactions of the life elements, which are mainly contemporaneous, direct, and immediate, do not suffice to form an organism. As soon as the grouping of chemical elements reaches the stage of an organism interaction also be- comes essential, for the chemical activities of one region of the ‘Loeb, Jacques, 1906, pp. 66-68. * Rutherford, Sir Ernest, 1915, p. 115. COORDINATION 57 organism must be harmonized with those of all other regions; the principle of interaction may apply at a distance and the results may not be contemporaneous. ‘This is actually inferred to be the case in single-celled organisms, such as the Ameba.! The interacting and coordinating form of lifeless energy which has proved to be of the utmost importance in the life processes is that recognized in the early part of the nineteenth century and denoted by the term catalysis, first applied by Berzelius in 1835. A catalyzer is a substance which modifies the velocity of any chemical reaction without itself being used up by the reaction. Thus chemical reactions may be accelerated or retarded, and yet the catalyzer lose none of its energy. In a few cases it has been definitely ascertained that the catalytic agent does itself experience a series of changes. The theory is that catalytic phenomena depend upon the alternate decomposition and recomposition, or the alternate attachment and detachment of the catalytic agent. Discovered as a property in the inorganic world, catalysis has proved to underlie the great series of functions in the organic world which may be comprised in the physical term interaction. ‘The researches of Ehrlich and others fully justify Huxley’s prediction of 1881 that through therapeutics it would become possible ‘‘to introduce into the economy a molecular mechanism which, like a cunningly contrived torpedo, shall find its way to some particular group of living elements and cause an explosion among them, leaving the rest untouched.” In fact, the interacting agents known as “‘enzymes”’ are such living catalyzers,? and accelerate or retard reactions in the body by forming intermediary unstable compounds which are rapidly decomposed, leaving the catalyzer (7. e., enzyme) free to repeat the action. Thus a small quantity of an enzyme 1 Calkins, Gary N., 1916, pp. 259, 260. * Loeb, Jacques, 1906, pp. 26, 28. 58 THE ORIGIN AND EVOLUTION OF LIFE can decompose indefinite quantities of a compound. The activity of enzymes is rather in the nature of the “interaction” of our theory than of direct action and reaction, because the results are produced at a distance and the energy liberated may be entirely out of proportion to the internal energy of the catalyzer. The enzymes, being themselves complex organic compounds, act specifically because they do not affect alike the different organic compounds which they encounter in the fluid circulation. ADAPTATION IN THE COLLOIDAL STATE In the lifeless world matter occurred both in the crystal- loidal and colloidal states. It is in the latter state that life originated. It is a state peculiarly favorable to action, reac- tion, and interaction, or the free interchange of physicochemi- cal energies. Each organism is in a sense a container full of a watery solution in which various kinds of colloids are sus- pended.! Such a suspension involves a play of the energies of the free particles of matter in the most delicate equilibrium, and the suspended particles exhibit the vibrating movement attributed to the impact of the molecules.?- These free parti- cles are of greater magnitude than the individual molecules; in fact, they represent molecules and multimolecules, and all the known properties of the compounds known as ‘‘colloids” can be traced to feeble molecular affinities between the molecules themselves, causing them to unite and to separate in multi- molecules. Among the existing living colloids are certain car- bohydrates, like starch or glycogen, proteins (compounds of carbon, hydrogen, oxygen, and nitrogen with sulphur or phos- phorus), and the higher fats. The colloids of protoplasm are dependent for their stability on the constancy of acidity and ‘ Bechhold, Heinrich, ror2. 2 Smith, Alexander, 1914, p. 305. FUNCTIONS OF LIFE ELEMENTS 59 alkalinity, which is more or less regulated by the presence of bicarbonates.! Electrical charges in the colloids? are demonstrated by cur- rents of electricity sent through a colloidal solution, and are interpreted by Freundlich as due to electrolytic dissociation of the colloidal particles, alkaline colloids being positively charged, while acid colloids are negatively charged. The concentration of hydrogen and hydroxyl ions in the ocean and in the organ- ism is automatically regulated by carbonic acid.® Among the colloidal substances in living organisms the so- called enzymes are very important, since they are responsible for many of the processes in the organism. Possibly enzymes are not typical colloids and perhaps, in pure form, they may not be classified as such; but if they are not colloids they cer- tainly behave like colloids. Cosmic PROPERTIES AND LIFE FUNCTIONS OF THE CHIEF CHEMICAL LIFE ELEMENTS Of the total of eighty-two or more chemical elements thus far discovered at least twenty-nine are known to occur in liv- ing organisms either invariably, frequently, or rarely, as shown in Table II of the Life Elements. Whether essential, fre- quent, or of rare occurrence, each one of these elements—as described below—has its single or multiple services to render to the organism. Hydrogen, the life element of least atomic weight, is always near the surface of the typical hot stars. Rutherford? tells us that, while the hydrogen atom is the lightest known, its nega- tively charged electrons are only about 1/1800 of the mass of 1 Henderson, Lawrence J., 1913, pp. 157-160. * Loeb, Jacques, 1906, pp. 34, 35. 3 Henderson, Lawrence J., 1913, p. 257. 4 Hedin, Sven G., 1915, pp. 164, 173. 5 Rutherford, Sir Ernest, 1915, p. 113. 60 THE ORIGIN AND EVOLUTION OF LIFE the hydrogen atom: they are liberated from metals on which ultra-violet light falls, and can be released from atoms of mat- Fic. 6. HypROGEN VAPOR IN THE SOLAR ATMOSPHERE Hydrogen, which far exceeds any other element in the amount of heat it yields upon oxidation (see Table II, p. 67) and ranks among the four most important of the chemical life elements, is also invariably present at the surface of all typical hot stars, includ- ing the sun. The large masses of hydrogen vapor known as “solar prominences” which burst forth from every part of the sun, are here shown as photographed during a total eclipse. The upper figure presents a detail from the lower, greatly enlarged From the Mount Wilson Observatory. ter by a variety of agencies. Hydrogen is present in all acids and in most organic compounds. It also has the highest FUNCTIONS OF LIFE ELEMENTS 61 power of combustion.' Its ions are very important factors in animal respiration and in gastric digestion.? It is very active in dissociating or separating oxygen from various compounds, and through its affinity for oxygen forms water (H;O), the principal constituent of protoplasm. Fic. 7. HypDROGEN FLOCCULI SURROUNDING A GROUP OF SUN-SPOTS. The vortex structure is clearly shown. After Hale. From the Mount Wilson Observatory. Oxygen, like hydrogen, has an attractive power which brings into the organism other elements useful in its various functions. It makes up two-thirds of all animal tissue, as it makes up one-half of the earth’s crust. Besides these attractive and syn- thetic functions, its great service is as an oxidizer in the release of energy; it.is thus always circulating in the tissues. Through this it is involved in all heat production and in all mechanical work, and affects cell division and growth.® 1 Henderson, Lawrence J., 1913, pp. 218, 239, 245. 2W.J.-Gies. 3 Loeb, Jacques, 1906, p. 16. 62 THE ORIGIN AND EVOLUTION OF LIFE Nitrogen comes next in importance to hydrogen and oxygen as structural material’ and when combined with carbon and sulphur gives the plant and animal world one of the chief organic food constituents, protein. It was present on the primordial earth, not only in the atmosphere but also in the gases and waters emitted by volcanoes. Combined with hy- drogen it forms various radicles of a basic character (e. g., NH: in amino-acids, NH,in ammonium compounds); combined with oxygen it yields acidic radicles, such as NO; in nitrates. It combines with carbon in — C = N radicles and in = C — NHz and == C — NH forms, the latter being particularly important in protoplasmic chemistry.? This life element forms the basis of all explosives, it also confers the necessary instability upon the molecules of protoplasm because it is loath to combine with and easy to dissociate from most other elements. Thus we find nitrogen playing an important part in the physiology of the most primitive organisms known, the nitrifying bacteria. Carbon also exists at or near the surface of cooling stars which are becoming red.* It unites vigorously with oxygen, tearing it away from neighboring elements, while its tendency to unite with hydrogen is less marked. At lower heats the carbon compounds are remarkably stable, but they are by no means able to resist great heats; thus Barrell‘ observes that a chemist would immediately put his finger on the element car- bon as that which is needed to endow organic substance with complexity of form and function, and its selection in the origin of plant life was by no means fortuitous. Including the arti- ficial products, the known carbon compounds exceed 100,000, while there are thousands of compounds of C, H, and O, and hundreds of C and H.? Carbon is so dominant in living mat- ‘Henderson, Lawrence J., 1913, p. 241. a W oe ee aes * Henderson, Lawrence J., 1913, p. 55. * Joseph Barrell, letter of March 20, 1916. * Henderson, Lawrence J., 1913, pp. 193, 194. FUNCTIONS OF LIFE ELEMENTS 63 ter that biochemistry is very largely the chemistry of carbon compounds; and it is interesting to observe that in the evolu- tion of life each of these biological compounds must have arisen suddenly as a saltation or mutation, there being no continuity between one chemical compound and another. Phosphorus is essential in the nucleus of the cell,! being a large constituent of the intranuclear germ-plasm known as chromatin, which is the seat of heredity. It enters largely into the structure of nerves and brain and also, in the form of phosphates of calcium and magnesium, serves an entirely diverse function as building material for the skeletons of animals. Phosphates are important factors in the maintenance of normal uniformity of reaction in the blood. Sulphur, uniting with nitrogen, oxygen, hydrogen, and car- bon, is an essential constituent of the proteins of plants and animals.” It is especially conspicuous in the epidermal protein known as keratin, which by its insolubility mechanically pro- tects the underlying tissues. Sulphur is also contained in one of the physiologically important substances of bile.* Sul- phates are important factors in the protective destruction, in the liver, of poisons of bacterial origin normally produced in and absorbed from the large intestine. Potassium is able to separate hydrogen from its union with oxygen in water, and is the most active of the metals, biologi- cally considered, in its positive lonization.® Through stimula- tion and inhibition potassium salts play an important part in the regulation of life phenomena, and they are essential to the living tissues of plants and animals, fresh-water and marine plants in particular storing up large quantities in their tissues.° 1Op. cit., p. 241. 2 Op. cit., p. 242. 3 Pirsson, Louis V., and Schuchert, Charles, 1915, p. 434. 4W. Js Gies: 5 Cesium is more electropositive.—F. W. Clarke. 6 Loeb, Jacques, 1906, p. 94. 64 THE ORIGIN AND EVOLUTION OF LIFE Potassium is of service to life in building up complex com- pounds from which the potassium cannot be dissociated as a free ion; it is thus one of the building stones of living matter.? Magnesium is fourth in order of activity among the metallic elements. It is essential to chlorophyll, the green coloring matter of plants, which in the presence of sunshine is able Fic. 8. THE SUN, SHOWING SUN-SPOTS AND CALCIUM VAPOR. Calcium, a life element essential to all plants and animals, and especially abundant in the bones and teeth of vertebrates, is also a constituent of the solar atmosphere, as shown by these two photographs of the sun, both displaying the same view and the same group of sun-spots. \ The one at the left, made by calcium rays alone with the spectro-heliograph,! shows in addition the clouds of calcium vapor which are not evident in the photograph at the right. From the Mount Wilson Observatory. _ 1 An instrument devised by Professor George E. Hale for taking photographs of the sun by the light of a single ray of the spectrum (calcium, hydrogen, etc.). to dissociate oxygen from the carbon of carbon dioxide and from the hydrogen of water. It is also found in the skeletons of many invertebrates and in the coralline alge, and is an im- portant factor in inhibiting or restraining many biochemical processes. Calcium is third in order of activity among the metallic elements. According to Loeb? it plays an important part in 1Qp. cit., p. 72. 2 Op. cit., 1906, p. 94. FUNCTIONS OF LIFE ELEMENTS 65 the life phenomena through stimulation (irritability) and in- hibition. It unites with carbon as carbonate of lime and is contained in many of those animal skeletons which, through deposition, make up an important part of the earth’s crust. HYDROGEN Fic. 9. CHEMICAL LIFE ELEMENTS IN THE SUN. Three regions of the solar spectrum with lines showing the presence of such essential life elements as carbon, nitrogen, calcium, iron, magnesium, sodium, and hydrogen. From the Mount Wilson Observatory. In invertebrates the carbonates, except in certain brachiopods, are far more important as skeletal material than the phosphates: the limestones form only about five per cent of the sedimen- taries. Shales and sandstones are far more abundant. Iron is essential for the production of chlorophyll,' though, unlike magnesium, it is not contained in it. It is present as well in all protoplasm, while in the higher animals it serves, in 1 Sachs, Julius, 1882, p. 699. 66 THE ORIGIN AND EVOLUTION OF LIFE the form of oxyhemoglobin, as a carrier of oxygen from the lungs to the tissues.’ Sodium is less important in the nutrition of plant tissues, but serves an essential function in all animal life in relation to movement through muscular contraction.” Its salts, like those of calcium, play an important part in the regulation of life phe- nomena through stimulation and inhibition.’ Iodine, with its negative ionization, becomes useful through its capacity to unite with hydrogen in the functioning of the brown alge and in many other marine organisms. It is also an organic constituent in the thyroid gland of the vertebrates. The iodine content of crinoids—stalked echinoderms—varies widely in organisms gathered from different parts of the ocean according to the temperature and the iodine content of the sea-water. Iodine and bromine are important constituents of the organic axes of gorgonias. Chlorine, like iodine, a non-metallic element with negative ions, is abundant in marine alge and present in many other plants, while in animals it is present in both blood and lymph. In union with hydrogen as hydrochloric acid it serves a very important function in the gastric digestion of proteins.° Barium, rarely present in plants, has been used in animal experimentation by Loeb, who has shown that its salts induce muscular peristalsis and accelerate the secretory action of the kidneys.® Copper ranks first in electric conductivity. In the inverte- brates, in the form of hemocyanine, it acts as an oxygen carrier in the fluid circulation to the tissues.’ It is always present in certain molluscs, such as the oyster, and also in the plumage : Henderson, Lawrence J., 1913, p. 241. * Loeb, Jacques, 1906, p. 79. 2 Op. cit., PP. 94, 95. 4 Henderson, Lawrence J., 1913, p. 242. © Op. cit, p. 242. 6 Loeb, Jacques, 1906, p. 93. 7 Henderson, Lawrence J., 1913, p. 241. TABLE II. ADAPTIVE FUNCTIONS OF THE LIFE ELEMENTS IN PLANTS AND ANIMALS Heat Combustion Per Gram Atomic Weight ae (H2) Element Hydrogen Carbon Oxygen Nitrogen Phosphorus Sulphur Potassium Magnesium Calcium Iron ?Sodium ?Chlorine ?Silicon Symbol Plants ELEMENTS INVARIABLY PRESENT IN LIVING ORGANISMS Animals Hydrogen, carbon, oxygen, and nitrogen—‘“H, C, O, N”—are essential and of chief rank in all life processes; forming, with sulphur, practically all plant and animal proteins and, with phosphorus, forming the nucleoproteins. In nucleoproteins and phospholipins. In most proteins, 0.15.0 per cent. Abundant in marine plants, esp. “‘kelps” (larger Pheophy- ce@); activity of chlorophyll depends on it. Present in large quantities in Corallinacee (a family of cal- cified red alge). Present in large quantities in certain alge (chiefly marine). Essential in the formation of protoplasm; present in chlo- rophyll. Believed essential to all plants, but not demonstrated; found in marine plants, esp. Pheophycee. Present in many plants; believed by some to be essential; abundant in marine alge, esp. in the Pheophycee. Found in all plants; present in large quantities in the Dia- tomacee, both fresh-water and marine; in form of “silica” constitutes o.5—7.0 per cent of the ash of ordinary marine alge. In nucleoproteins and phospholipins; in some brachiopods; in blood; and in vertebrate bone and teeth. In most proteins, o.1—-5.0 per cent. In blood, muscle, etc. Present in echinoderms and alcyonarians; present in all parts of vertebrates, esp. in bones. In all parts of vertebrates; abundant in bones and teeth. Essential in the formation of protoplasm, and in the higher animals; essential in hemoglobin as an oxygen- carrier. Present in all animals; abundant in blood and lymph. Present in all animals; abundant in blood and lymph; present in the gastric juice. Present in .radiolarians and siliceous sponges; also in all the higher animals. 0.1766 cal. ELEMENTS FREQUENTLY PRESENT IN LIVING ORGANISMS Iodine Manganese Bromine Fluorine In marine plants, esp. the “brown alge,’ Phaeophycee ; in Laminaria and Fucus; also in some Gorgonias. In some plants. In marine plants, esp. the “brown alge,’ Pheophycee; in some Gorgonias. In a few plants. Essential in the higher animals (thyroid). In most animals in very slight proportions. In some animals in very slight proportions. In some animals—constituent of bones and _ teeth; shells of mollusks and in vertebrate bones. ELEMENTS RARELY PRESENT IN LIVING ORGANISMS 1.407 1.291 The exceedingly rare occurrence 0 1 Commonly regarded as poisons Ww. Aluminum ! Arsenic ' Barium ' Boron Cobalt ! Copper ! Lead ! Lithium Nickel ! Radium ! Strontium ! Zinc ! In a few plants. In a few plants. In some plants. In a few plants. In a few plants. In some plants. In a few plants. In some plants. In a few plants. In a few plants. f cerium, chromium, didymium, lanthanum, molybdenum, and vanadium is in all probability merely adventitious. hen present in mineral (ionic) forms, even in small proportions. In a few animals. In some animals. Traces in some corals; essential in some lower animals as oxygen-carrier. | Traces in some corals, In some animals. In a few animals; traces in some corals. —_———— $$ PRIMARY STAGES OF LIFE 67 of a bird, the Turaco. Although among the rare life elements it ranks first in toxic action upon fungi, alge, and in general upon all plants, yet it is occasionally found in the tissues of trees growing In copper-ore regions.! | In general most of the metallic compounds and several of the non-metallic compounds are toxic or destructive to life when present in large quantities. All the mineral elements of high atomic weight are toxic in comparatively minute propor- tions, while the essential life elements of low atomic weight are toxic only in comparatively large proportions. Toxicity depends largely upon the liberation of ions, and non-ionized and non-ionizable organic compounds—such as hemoglobin containing non-ionizable iron—are wholly non-toxic. PURE SPECULATION AS TO THE PRIMARY PHYSICOCHEMICAL STAGES: OF —LIFE The mode of the origin of life is a matter of pure specula- tion, in which we have as yet little observation or uniformitarian reasoning to guide us, for all the experiments of Biitschli and others to imitate the original life process have proved fruitless. We shall, however, from our knowledge of bacteria (see Chap. III) put forward five hypotheses in regard to it, considering the life process as probably a gradual one, marked by short leaps or accessions of energy, and not as a sudden one. First: We may advance the hypothesis that an early step in the organization of living matter was the assemblage one by one of several of the ten elements now essential to life, namely, hydrogen, oxygen, nitrogen, carbon, phosphorus, sulphur, po- tassium, calcium, magnesium, and iron (also perhaps silicon), which are present in all living organisms, with the exception of some of the most primitive forms of bacteria which may 1M. A. Howe, letter of February 24, 1916. 68 THE ORIGIN AND EVOLUTION OF LIFE lack magnesium, iron, and silica. Of these the four most im- portant elements were obtained from their previous combina- tion in water (H.O), from the nitrogen compounds of volcanic emanations or from the atmosphere! consisting largely of nitrogen, and from atmospheric carbon dioxide (CO.). The remaining six elements, phosphorus, sulphur, potassium, cal- clum, magnesium, and iron, came from the earth. Second: Whether there was a sudden or a more or less serial grouping of these elements, one by one, we are led to a second hypothesis that they were gradually bound by a new form of mutual attraction whereby the actions and reactions of a group of life elements established a new form of unity in the cosmos, an organic unity, an zndividual or organism quite distinct from the larger and smaller aggregations of inorganic matter pre- viously held or brought together by the forces of gravity. Some such stage of mutual attraction may have been ancestral to the cell, the primordial unity and individuality of which we shall describe later. Third: This leads to the hypothesis that this grouping oc- curred in the gelatinous state described as “colloidal” by Graham.’ Since all living cells are colloidal, it appears prob- able that this grouping of the “‘life elements” took place in a state of colloidal suspension, for it is in this state that the life elements best display their incessant action, reaction, and interaction. Bechhold? observes that ‘“‘ Whatever the arrange- ment of matter in living organisms in other worlds may be, it must be of colloidal nature. What other condition except the * Ammonia is also formed by electrical action in the atmosphere and unites with the nitric oxides to form ammonium nitrate or nitrite; these compounds fall to earth in rain. —F. W. Clarke. * Over fifty years ago Thomas Graham introduced the term “colloid” (L. colla, glue) to denote non-crystalloid indiffusible substances, like gelatine, a typical colloid, as dis- tinguished from diffusible crystalloids. Proteins belong to that class of colloids which, once coagulated, cannot, as a rule, be redissolved in water. * Bechhold, Heinrich, 1912, p. 194. NEW ORGANIC COMPOUNDS 69 colloidal could develop such changeable and plastic forms, and yet be able, if necessary, to preserve these forms unaltered ?”’ Fourth: As a fourth hypothesis relating to the origin of organisms, we may advocate the idea that the evolution and specialization of various “chemical messengers’? known as catalyzers (including enzymes or ‘‘unformed ferments’’) has proceeded step by step with the evolution of plant and animal functions. In the evolution from the single-celled to the many- celled forms of life and the multiplication of these cells into hundreds of millions, into billions, and into trillions, as in the larger plants and animals, biochemical coordination and cor- relation became increasingly essential. This cooperation was also an application of energy new to the cosmos. Fifth: With this assemblage, mutual attraction, colloidal condition, and chemical coordination, a fifth hypothesis is that there arose the rudiments of competition and Natural Selection which tested all the actions, reactions, and inter- actions of two competing individuals. Was there any stage in this grouping, assemblage, and organization of life forms, how- ever remote or rudimentary, when the law of natural selection did not operate between different unit aggregations of matter? Probably not, because each of the chemical life elements possesses its peculiar properties which in living compounds best serve cer- tain functions. EVOLUTION OF NEW ORGANIC COMPOUNDS Special actions and reactions appear to be characteristic of each of the life elements, issuing in new compounds. The central idea in our five hypotheses (see p. 67) of suc- cessive physicochemical stages is that in the origin and early evolution of the life organism there was a gradual attraction and grouping of the ten chief life elements, followed by the 70 THE ORIGIN AND EVOLUTION OF LIFE grouping of the nineteen or more chemical elements which were subsequently added. The creation of new chemical compounds may have been analogous to the successive addition of new characters and functions, such as we now observe through paleontology in the origin and development of the higher plants and animals, resembling a series of inventions and dis- coveries by the organism. Conceivable steps in the process were as follows: From earth, air, and water there may have been an early grouping of oxygen, nitrogen, hydrogen, and carbon, such as we witness in the lowliest bacterial stages of life. Even those lifeless com- pounds which contain neither hydrogen, carbon, nor oxygen, make up but a very small percentage of the substance of known bodies. The compounds of carbon, hydrogen, and oxygen (C, H, O)! constitute a unique ensemble of fitness among all the possible chemical substances for the exchange of matter and energy within the life organism and between it and its environment. As the higher forms of life are constituted to- day, water and the carbon dioxide of the atmosphere are the chief materials of the complicated life compounds, and also the common end products of the materials yielding energy to the body. Proteins are made from materials containing nitro- gen in addition. Thus may have arisen the utilization of the binary com- pounds of carbon and oxygen (CO,), and of hydrogen and oxygen (H2O), to the attractive power of which Henderson? has especially drawn our attention. It is this attractive power of oxygen or of hydrogen or of both elements combined which is now bringing, and in the past may have brought into the life organism other elements useful to it in its various func- * Henderson, Lawrence J., 1913, pp. 71, 194, 195, 207, 231, 232. 2 Op. cit., Pp. 239, 240. INTERACTIONS aI tions. Thus in the origin of life hydrogen and oxygen, ele- ¢ ments unrivalled in chemical activity, functioned as “‘attrac- tive”’ agents to enable the life organism to draw in other chem- ical elements to serve new purposes and functions. Through such attraction or other means the incorporation of the active metals—potassium, sodium, calcium, magnesium, iron, manganese, and copper—into the substance of living organisms may have occurred in the order of their utility in capturing energy from the environment and storing it within the organism. For example, an immense period of geologic time may have elapsed before the addition of magnesium and iron to certain hydrocarbons enabled the plant to draw upon the energy of solar light. This marked the appearance of chlorophyll in the earliest algal stage of plant life. EVOLUTION OF INTERACTIONS The organism as a whole is made a harmonious unit through interaction. Its actions and reactions must be regu- lated, balanced, coordinated, correlated, protected from foreign invasion, accelerated, retarded. This harmony seems in large part to be due to the principle that every action and reaction sends off as a by-product a “chemical messenger’? which sooner or later produces an interaction at some more or less distant point. The regulating and balancing of actions and reactions within the organism was provided for by the presence in the fluid cir- culation of outside chemical agents, for many of the primordial actions and reactions are known to give rise to chemical by- products which circulate throughout the life organism. Among such regulating and balancing influences we observe that ex- erted by the phosphates upon the acidifying tendency of carbon 42 THE ORIGIN AND EVOLUTION OF LIFE dioxide;! in respiration carbon dioxide raises the hydrogen con- centration of the blood; the phosphates restrain this tendency, while the breathing apparatus, in response to stimuli from the respiratory centres irritated by the hydrogen, throws out the excess of this element. | Thus there evolved step by step the function of coordinating and correlating the activities of various parts of the life organ- ism remote from each other by means of chemical messen- gers adapted to effect not only a general imlteraction between general parts, but also special interactions between special parts; for it is now known that, as Huxley prophesied (see p- 57), certain chemical messengers do reach particular groups of living elements and leave others entirely untouched. For example, the enzyme developed in the yeast ferment produces a different result in each one of a series of closely related carbo- hydrates.’ These chemical messengers are doubtless highly diversified; they are now known to exist in at least three or four forms, as follows: First: The simplest forms of such chemical messengers are those which originate as by-products of single chemical reactions. For example, the carbon dioxide (CO,) liberated in the cell by the reactions of respiration acts at a distance on other portions of the cell and of the organism. Thus every cell of the body furnishes in the carbon dioxide which it eliminates a chemical messenger,’ since under normal conditions the carbon dioxide of the blood is one of the chief regulators of the respiratory centre, influencing this centre by virtue of its acidic properties. Second: Of prime importance among the various “‘ chemical messengers’’ are the organic catalyzers! known as enzymes, the : W. J. Gies. * Moore, F. J., 1915 p. 170; Loeb, Jacques, 1906, pp. 21, 22. * Abel, John J., rors, p. 168. _ 4 Loeb, Jacques, 1906, pp. 8, 28. CHEMICAL MESSENGERS 73 action of which has already been described (see p. 57). They appear to be present in all cells, and in most cases the ac- tivity of the cell itself depends upon them.! These enzymes are very probably of a protein nature and are readily destroyed by heat in the presence of water. The active agents of the external secretions when present are always of the nature of a ferment or enzyme. Driesch? has suggested that the nucleus of the cell is a storehouse of these ferments which pass out into the protoplasm tissues and there set up specific activities. Third: Antigens, antibodies including the agents of immunity. The active and inactive protein compounds termed antigens in- clude certain known proteins and possibly a few other com- pounds of kindred nature. Among the active protein compounds are certain enzymes, bacterial poisons, snake venoms, spider poisons, and some vegetable poisons; antigens of this class are all powerfully active and possess properties which suggest that they may eventually be classed as enzymes. On the invasion of an organism by any foreign protein of this class in any region except the interior of the alimentary canal it would seem that certain chemical messengers called antibodies arise which are especially fitted to protect the tissues of the body against such invasion; these antibodies are true agents of im- munity and serve to increase the resistance of the organism to any future attack of the invading antigen; it is to this forma- tion of neutralizing antibodies, known as antitoxins, that the curative powers for such infections as diphtheria and tetanus are due. There are also antigens of another kind, consisting of znac- tive protein compounds, which, when they invade an organism, induce the formation of antibodies acting in an entirely dif- 1 Schafer, Sir Edward A., 1916, pp. 4, 5. 2 Wilson, Edmund B., 1906, p. 427. 3 Zinsser, Hans, 1915, pp. 223-226, 247, 248. 74 THE ORIGIN AND EVOLUTION OF LIFE ferent manner from the antitoxins. While antibodies of this kind tend to assimilate or remove the invading antigen, they do not confer immunity against a future invasion: on the con- trary, they render the organism increasingly susceptible. Ex- periments on animals show that, while the first injection of such inactive proteins may be entirely harmless, subsequent injections may result in severe injury or even death. It is, therefore, evident that the invasion of an organism either by a powerfully active or by an inactive antigen causes changes of a physicochemical nature which appear to originate in the body cell itself, resulting in the formation of chemical messengers known as antibodies which appear in the circulat- ing blood. Fourth: Of vital importance to the life organism are those chemical messengers known as internal secretions, due for the most part to the so-called endocrine (Gr. &dov, within, and xpivw, to separate) organs or ductless glands, which liberate some specific substance within their cells that passes directly into the blood stream and has a stimulating or inhibiting effect upon other organs. ‘To certain of these stimulating internal messengers Starling applied the term “hormone” (Gr. oppdoa, to awaken, to stir up). Recently Schafer,! in reviewing all the organs of internal secretion, has proposed the opposite term “‘chalone” (Gr. yadda, to make slack) for those messen- gers which depress, retard, or inhibit the activity of distant parts of the body. The interactions between different parts of the organism produced by these chemical messengers depend upon a simpler chemical constitution than that of the enzymes,’ as hormones and chalones, for the most part, are not rendered inactive, even by prolonged boiling. We may suppose that in the course of evolution certain * Schafer, Sir Edward A., 1916, p. 5s. 2 Loc. cit. CHEMICAL MESSENGERS 75 special cells and, finally, special groups of cells gave rise to the glands, and none of the discoveries we have hitherto de- scribed throws greater illumination on the whole process of building up an elaborate life organism than those connected with the products of internal secretion. Among the special glands of internal secretion known in man are the thyroids, parathyroids, thymus, suprarenals, pituitary body, and pineal gland, rudiments of which doubtless occur in the very oldest vertebrates and even among their invertebrate ancestors; al- though their functions have been discovered chiefly through experiment upon the lower mammals and man. Of the chemical messengers produced by these glands some affect the growth of the entire organism, while others affect only certain parts of the organism; some arrest growth entirely, others stimulate growth at certain points only, and others again entirely change the proportions of certain parts of the body. Thus an injury to the pituitary body, which lies beneath the vertebrate brain, results in stunted stature, marked adiposity, and delayed or imperfect sexual development; on the other hand, a diseased condition of the pituitary body, rousing it to excessive function, is followed by a great increase in the general size of the head, as well as by a complete change in the proportions of the face from broad to long and narrow, and an abnormal growth of the long limb-bones, while at the same time the proportions of the hands are changed from nor- mal to the short and broad condition known as brachydactyly.! In other words, the regulation and balance resulting in the normal size and proportions of certain parts of the skeleton are dependent upon chemical messengers coming from these glands. 1Schafer, Sir Edward A., 1916, pp. 107, 108, 110. Cushing, Harvey, 1911, pp. 255 ons 76 THE ORIGIN AND EVOLUTION OF LIFE It has also been discovered that the source of such internal secretions is not confined to the ductless glands, but that cer- tain duct-glands, such as the ovaries, testes, and pancreas, serve a double function, for they secrete not only through their ducts, but they also produce an internal secretion which enters the circulation of the blood. It is, of course, a fact known from remote antiquity that removal of the sex Fic. 10. HAND Form DETERMINED BY HEREDITY (A) AND BY ABNORMAL INTERNAL SECRETIONS (B, C). A. Hereditary brachydactyly (partial) attributed to congenital causes. After Drinkwater. B. Acquired brachydactyly. This abnormally broad and stumpy hand shows one of the results of abnormally excessive secretions of the pituitary gland. After Cushing. C. Acquired dolichodactyly. This slender hand with tapering fingers shows one of the results of abnormally insufficient secretions of the pituitary gland. After Cushing. glands from a young animal of either sex not only inhibits the development of all the so-called secondary sexual characters, but favors the development of characters of the opposite sex. During the last and present centuries it has been discovered that all these inhibited characters may be restored by success- fully transplanting or grafting into some part of the body the ovary or testicle, either from the same or another individual, thus proving that in both sexes the secondary sexual characters CHEMICAL MESSENGERS a7 are dependent upon some internal secretion from the ovaries and testes and not upon the normal production of the male and female germ-cells, or ova and spermatozoa. The classic demonstration of this internal messenger sys- tem is that made experimentally by Berthold in fowls. In 1849 he transplanted the testicles of young cocks which after- ward developed the masculine voice, comb, sexual desire, and love of combat, thus anticipating the theories of Brown- Sequard, who committed himself to the view that a gland, ductless or not, sends into the circulation substances essential to the normal growth and maintenance of many if not all parts of the body. With the discovery that the regulating and balancing func- tions, as well as the accelerating or retarding of the activities of certain characters of organisms, are phenomena of physico- chemical action, reaction, and interaction in individual devel- opment, we obtain a distant glimpse of the possible causes of the balance, development, or degeneration of certain parts of organisms through successive generations, and conceivably of the long-sought means of interaction between the actions and reactions of individual development (body-protoplasm and body-chromatin) and of the germ-cells in race development (heredity-chromatin). In fact, a heredity hypothesis was proposed by Cunning- ham! in 1906 based upon Berthold’s discovery that the connec- tion between the germ-cells and the secondary sexual organs of the body was really of a chemical rather than of a nervous nature as had previously been supposed. To paraphrase Cun- ningham’s hypothesis in modern terms, since hormones and chalones issuing as internal secretions from the groups of germ- cells (ovaries and testes) determine the development of many 1 Cunningham, J. T., 1908, pp. 372-428. 78 THE ORIGIN AND EVOLUTION OF LIFE other organs, it is possible that hormones and chalones arising from the various cellular activities of the body itself may act upon the physicochemical elements in the germ-cells which correspond potentially to the tissues from which these hor- mones and chalones are derived. Cunningham was a strong believer in the Lamarckian explanation (see p. xiii) of evolu- tion, and his heredity hypothesis was designed to suggest a means by which the modifications of the body due to environ- mental and developmental conditions could so modify the corresponding tissues and physicochemical constitution of the chromatin in the germ-cells as to become hereditary and re- appear in subsequent generations. PHYSICOCHEMICAL DIFFERENTIATION As the result of recent investigations of cancer, Loeb! comes to the following conclusions: ‘““We must assume that every individual of a certain species differs in a definite chemical way from every other of that species, and that in its chemical constitution an animal of one species differs still more from an animal of another. Every cell of the body has a chemical character in common with ev- ery other cell of that body and also in common with the body fluids; and this particular chemical group differs from that of every other individual of the species and to a still greater de- gree from that of any individual of another group or species. Thus it happens that cells belonging to the same organism are adapted to all the other cells of that organism and also to the body fluids. .. . “Tt has been possible to demonstrate by experimental methods that there are fine chemical differences not only be- tween different species and between different individuals of 1 Loeb, Leo, 1916, pp. 209-226. PHYSICOCHEMICAL DIFFERENTIATION 79 the same species, but also between different sets of families which constitute a strain, for certain chemical characters dif- ferentiate them from other strains of the same species. It has been shown, for instance, that white mice bred in Europe differ chemically from white mice bred in America, although the appearance of both strains may be identical.” The investigations of Reichert and Brown (cited in Chapter VIII, p. 247) give an insight into the almost inconceivable physicochemical complexity of a single element of the blood, namely, the oxyhemoglobin crystals. GHAR EE Rag tii ENERGY EVOLUDION OF BAGTERTAS ARGH AND GE GANGES Energy and form. Primary stages of biochemical evolution in bacteria. Evo- lution of protoplasm and chromatin, the two structural components of the living world. Chlorophyll and the energy of sunlight. Evolution of the alge. Some physicochemical contrasts between plant and animal evo- lution. We shall now trace some of the physicochemical principles of action, reaction, and interaction as they actually appear in operation in some of the simpler forms of life, beginning with the bacteria. In the bacterial organisms the capture, storage, release, and interaction of energy are what is best known and apparently most important, while their form is less known and apparently less important. PRIMARY STAGES OF BIOCHEMICAL EVOLUTION IN BACTERIA A bacterialess earth and a bacterialess ocean would soon be uninhabitable either for plants or animals; conversely, it is probable that bacteria-like organisms prepared both the earth and the ocean for the further evolution of plants and animals, and that life passed through a very long bacterial stage. In the origin of life bacteria appear to lie half-way be- tween our hypothetical chemical precellular stages (pp. 67-71) and the chemistry and definite cell structure of the lowliest plants, or alge. Owing to their minute size or actual invisibil- ity, bacteria are classified less by their shape than by their chemical actions, reactions, and interactions, the analysis of which is one of the triumphs of modern research. 80 EVOLUTION OF BACTERIA SI The size of bacteria is in inverse ratio to their importance in the primordial and present history of the earth. The largest known are slightly above 1/20 of a millimetre in length and 1/200 of a millimetre in width.! The smaller forms range from 1/2000 of a millimetre to organisms on the very limit of microscopic vision, 1/5000 of a millimetre in size, and to the bacteria beyond the limits of microscopic vision, the existence of which is inferred in certain diseases. The chemical consti- tution of these microscopic and ultramicroscopic forms is doubtless highly complex. The number of these organisms is inconceivable. In the daily excretion of a normal adult human being it is estimated that there are from 128,000,000,000 to 3.3,000,000,000,000 bacteria, which would weigh approximately 5 5/10 grams when dried, and that the nitrogen in this dried mass would be about 0.6 gram, constituting nearly one-half the total intestinal nitrogen.’ The discovery of the chemical life of the lowliest bacteria marks an advance toward the solution of the problem of the origin of life as important as that attending the long-prior dis- covery of the chemical action of chlorophyll in plants. In their power of finding energy or food in a lifeless world the bacteria known as prototrophic, or ‘“‘primitive feeders,”’ are not only the simplest known organisms, but it is probable that they represent the survival of a primordial stage of life chemistry. ‘These bacteria derive both their energy and their nutrition directly from inorganic chemical compounds: such types were thus capable of living and flourishing on the lifeless earth even before the advent of continuous sunshine and long 1 The influenza bacillus, 5/10 X 2/10 of a micron (1/10oo mm.) in size, and the germ of infantile paralysis, measuring 2/10 of a micron, are on the limit of microscopic vision. Beyond these are the ultramicroscopic bacteria, beyond the range of vision, some of which can pass through a porcelain filter. See Jordan, Edwin O., 1908, pp. 52, 53. 2 Kendall, A. I., 1915, p. 200. 82 THE ORIGIN AND EVOLUTION OF LIFE | before the first chlorophyllic stage (Algz) of the evolution of plant life. Among such bacteria, possibly surviving from ) Archeeozoic time, is one of these “‘primitive feeders,’ namely, the Nitroso monas of Europe.'| For combustion it takes in oxygen directly through the intermediate action of iron, phos- phorus, or manganese, each of the single cells being a powerful little chemical laboratory which contains oxidizing catalyzers, the activity of which is accelerated by the presence of iron and of manganese. Still in the primordial stage, Nitroso monas lives on ammonium sulphate, taking its energy (food) from the nitrogen of ammonium and forming nitrites. Living sym- biotically with it is Nitrobacter, which takes its energy (food) from the nitrites formed by Nztroso monas, oxidizing them into nitrates. Thus these two species illustrate in its simplest form our law of the interaction of an organism (Nitrobacter) with its life environment (Nitroso monas).? These organisms are wide-spread: Nztroso monas is found in Europe, Asia, and Africa, while Nitrobacter appears to be almost universally distributed. These “primitive feeders”’ are classed among the nitrifying bacteria because they take up the nitrogen of ammonia com- pounds. Heraeus and Hiippe (1887) were the first to observe these nitrifiers in action in the soils and to prove that pre- chlorophyllic organisms were capable of development, with ammonium and carbon dioxide as their only sources of energy. Nine chemical “life elements’? are involved in the life reac- tions of these organisms, namely, sodium, potassium, phos- phorus, magnesium, sulphur, calcium, chlorine, nitrogen, and carbon. This discovery was confirmed by Winogradsky (1890, 1895), who showed that the above two symbiotic groups ex- isted; one the: nitrite formers, Nitroso monas, and the other the ‘Fischer, Alfred, 1900, pp. 51, 104. 2 Jordan, Edwin O., 1908, pp. 492-497. EVOLUTION OF BACTERIA 83 nitrate formers, Nitrobacter. These bacteria are not only in- dependent of life compounds, but even small traces of organic carbon and nitrogen compounds are injurious to them. Later Nathanson (1902) and Beyjerinck (1904) showed that certain sulphur bacteria possess similar powers of converting ferrous to TeMuGrOxidesa nds LiccimtO wo U)s: Such bacterial organisms may haye flourished on the lifeless earth and chemically prepared both the earth and the waters for the lowly forms of plant life. The relation of the nitrifying bacteria to the decomposition of rocks is well summarized by Clarke in the following passage:! ‘‘Even forms of life so low as the bacteria seem to exert a definite influence in the decom- position of rocks. A. Miintz has found the decayed rocks of Alpine summits, where no other life exists, swarming with the nitrifying ferment. ‘The limestones and micaceous schists of the Pic du Midi, in the Pyrenees, and the decayed calcareous schists of the Faulhorn, in the Bernese Oberland, offer good examples of this kind. The organisms draw their nourishment from the nitrogen compounds brought down in snow and rain; they convert the ammonia into nitric acid, and that in turn corrodes the calcareous portions of the ‘rocks. A. Stiitzer and R. Hartleb have observed a similar decomposition of cement by nitrifying bacteria. The effects thus produced at any one point may be small, but in the aggregate they may become appreciable. J. C. Branner, however, has cast doubts upon the validity of Miintz’s argument, and further investigation of the subiect seems to be necessary.” It is noteworthy that it is the nitrogen derived from waters and soils, rather than from the atmosphere, which plays the chief part in the life of these organisms; in a sense they repre- sent an early carbon stage of chemical evolution; since carbon 1 Clarke, F. W., 1916, p. 485. 84 THE ORIGIN AND EVOLUTION OF LIFE ‘is not their prime constituent, also adaptation to an earth-and- water environment rather than to an atmospheric one. In our portrayal of the chemistry of the lifeless earth it is shown how the chief life elements essential for the energy and nutrition of the nitrifying bacteria, namely, sodium, potassium, calcium, and magnesium, with potassium nitrite and ammo- nium salts as a source of nitrogen, may have accumulated in the waters, pools, and soils. These bacteria were at once the soil-forming and the soil-nourishing agents of the primal earth; they throve in the presence of energy-liberating compounds of extremely primitive character. It is important to note that water and air are essential to vigorous ammonium reactions, whether at or near the surface. In arid regions at the present time the ammonifying bacteria do not exist on the dry surface rocks, but act vigorously in the soils, not only at the surface, but also in the lower layers at depths of from six to ten feet, where moisture 1s constant and the porous soil well aérated,! thus giving rise to a nitrogen-nourished substratum, which explains the deep rooting of desert-dwelling plants. A second point of great significance is that these nitrifying organisms are heat-loving and light-avoiding; they are dependent on the heat of the earth or of the sun, for, like all other bac- teria, they carry on their activities best in the absence of sun- shine, direct sunlight being generally fatal. The sterilizing effect of sunlight is due partly to the coagulation of the bac- terial colloids by the rays of ultra-violet light. The sensitive- ness of bacteria to sunlight cannot, however, be viewed as evidence against their geologic antiquity, because their undif- ferentiated structure and their ability to live on inorganic foodstuffs even without the aid of sunshine seem to favor the idea that they represent a very primitive form of life.’ * Lipman, Charles B., 1912, pp. 7, 8, 16, 17, 20. *J. J. Kligler. EVOLUTION OF BACTERIA 85 The great geologic antiquity even of certain lower forms of bacteria which feed on nitrogen is proved by the discovery, announced by Walcott! in 1915, of a species of pre-Paleeozoic Al B C D E F Fic. 11. Fosst~n AND LIvING BACTERIA COMPARED. Extremely ancient fossil bacteria (4) compared with similar types of living bacteria (B-F), A. Fossil bacteria from the pre-Cambrian Newland limestone (Algonkian), after Walcott. B. Existing nitrifying bacteria found in soils—the arrow indicates a chain series similar to that of Walcott’s fossil bacteria. C. A more complex type of nitrifying bacteria found in soils. D. Nitrogen-fixing bacteria from the root nodules of legumes. Note the granular struc- ture of the supposed “chromatin.” E. Denitrifying bacteria found in soil and water. ¢ F. Bacteria stained to bring out the chromatin granules or “nuclei” in the centre of each rod-like bacterial cell. fossil bacteria attributed to ‘‘ Micrococcus,’ but probably related rather to the existing Nitroso coccus, which derives its nitrogen from ammonium salts. These fossil bacteria were found in a section of a chlorophyll- 1 Walcott, Charles D., 1915, p. 256. 86 THE ORIGIN AND EVOLUTION OF LIFE bearing algal plant from the Newland limestone of the Algon- kian of Montana, the age of which is estimated to be about 33,000,000 years. They point to a very long antecedent stage of bacterial evolution. In this section (Fig. 11, A), at the points indicated by the arrows, there is a little chain of cells closely similar to those in the existing species of Azotobacter, an organism that fixes atmospheric nitrogen and converts it into a form utilizable by the plant. The Algonkian form is related to the other nitrifiers, Nztroso coccus, Nitroso monas, and to Nitrobacter which lives on simple salts with carbon dioxide (CO:) as a source of carbon. The gradual evolution of a cellular structure in these organ- isms can be partly traced despite their excessively minute size. The cell structure of the Algonkian and of the recent Nitroso coccus bacteria (Fig. 11, 4, B) is very primitive and uniform in appearance, the protoplasm being naked or unprotected; this primitive structure is also seen in C, another type of nitrogen- fixer of the soil, which is chemically more complex because it can obtain its nitrogen either from the inorganic nitrogen compounds or from the organic nitrogen compounds (amino- acids), which are fatal to the Nitroso monas and the Nitro- bacter forms. The arrow points to a group of cells similar in appearance to those in B. A higher stage of granular structure appears in D, a nitrogen-fixer from the root nodules of legumes, which like B and C lives on inorganic chemical compounds, but draws upon the atmosphere for nitrogen and upon sugar for its carbon; we observe an uneven granular structure in this cell. This may be an illustration of an early type of parasitic adaptation. The next type of bacterium (£) is a denitrifier, which derives its oxygen from the nitrates, reducing them to nitrites and free nitrogen and ammonia. A further stage of structural and chemical evolution is seen (/) in four elongated EVOLUTION OF BACTERIA 87 bacteria, each showing a rod-like but cellular form with a deeply staining chromatin or nuclear mass; the arrows point to cells showing these chromatin granules. This organism is chemically more complex in that it can secrete a powerful tryptic-like enzyme which enables it to utilize complex poly- peptids and proteins (casein). Also it is an obligatory aérobic type, being unable to function in the absence of free oxygen. It was only after the chlorophyllic, carbon-storing true plants had evolved that the second great group of parasitic nitrifying bacteria arose to develop the power of capturing and storing the nitrogen of the atmosphere through life association or symbiosis with plants, also of deriving their carbon, not from inorganic compounds, but from the carbohydrates of plants. Such users of atmospheric nitrogen and of plant carbon include three general types: B. radicicola, associated with the root formation of legumes (compare D, Fig. 11), Clostridium (anaér- obic, z. e., independent of free oxygen), and Azotobacter (aérobic, i. €., requiring free oxygen).! It seems that the early course of bacterial evolution was in the line of developing a variety of complex molecules for per- forming a number of metabolic functions, and that the visible cell differentiation came later.2 Step by step the chemical evolution and addition of increasingly complex actions, reac- tions, and interactions appear to correspond broadly with the structural evolution of the bacterial organism in its approach to the condition of a typical cell with its cell-wall, protoplasm, and chromatin nucleus. To sum up, the existing bacteria exhibit a series of primor- dial physicochemical phases in the capture, storage, and utiliza- tion of energy, and in the development of products useful to themselves and to other organisms and of by-products which 1 Jordan, Edwin O., 1908, pp. 484-491. 21.J. Bligler, 838 THE ORIGIN AND EVOLUTION OF LIFE -as chemical messengers cause interactions in other organisms. With the simplest bacteria which live directly on the lifeless world we find that most of the fundamental chemical energies of the living world are already established, namely: (a) the colloidal cell interior, with all the adaptations of col- loidal suspensions, including (b) the stimulating electric action and reaction of the metallic on the non-metallic elements; for example, the accelera- tions by iron, manganese, and other metals. Some bac- teria carry positive, others negative ion charges; (c) the catalytic messenger, or enzyme action, both within and without the organism; (d) the protein and carbon energy storage, the primary food supply of the living world. Thus the chemical reactions of bacteria are analogous to those of the higher plant and animal cells. Considering bacteria as the primordial food supply, it is the invariable presence of nitrogen which distinguishes the bacteria making up their proteins; nitrogen is also a large con- stituent of all animal proteins. PERCENTAGE OF ELEMENTS IN THE PROTEINS ! Hydrogen Oxygen Nitrogen Sulphur Bacterial suspensions manifest the characteristics of col- loidal suspensions, namely, of fluids containing minute gelat- inous particles which are kept in motion by molecular move- ‘Moore, F. J., 1915, p. 199. Nucleic proteins contain a notable amount of phos- phorus as well. EVOLUTION OF .BACTERIA 89 ment: these colloidal substances have the food-value of protein and form the primary food of many Protozoa, the most ele- mentary forms of animal life. Chemical messengers in the form of enzymes of three kinds exist, proteolytic, oxidizing, and synthetic.! The proteolytic enzymes are similar to the tryptic enzymes of animals, being able to digest only the proteoses and simple proteins (casein, albumin) but not the complex proteins. Powerful oxidizing enzymes are present, but their character is not known. Synthetic enzymes, bringing together new living chemical compounds, must also exist, though as yet there is no positive information concerning them. Armed with these physicochemical powers, which may have been acquired one by one, the primordial bacteria begin to mimic the subsequent evolution of the higher plant and animal world by an adaptive radiation into groups which respectively seek new sources of energy, either directly from the inorganic world or parasitically from the developing organic bacterial and plant foods in protein and carbohydrate form, the different groups living together in large communities and interacting chemically upon one another by the changes pro- duced in their environment. The parasitic life of bacteria, beginning with their symbiotic relations with other bacteria, was extended into intimate rela- tions with the plants and finally with the entire living world. Like other forms of life, bacteria need oxygen for combus- tion in their intracellular actions and reactions; but free oxygen is not only unnecessary but actually toxic to the anaérobic bacteria, discovered by Pasteur in 1861, which derive their oxygen from inorganic and organic compounds. There is, however, a transitional group of bacteria, known as the faculta- live anaérobes, which can use either free or combined oxygen, 1T. J. Kligler. go THE ORIGIN AND EVOLUTION OF LIFE thus forming a link to all the higher forms of life in which free oxygen is an absolute essential. There is a group of the higher spore-forming bacteria which must have free oxygen. These constitute probably a late stage in bacterial evolution and form the link to the higher forms. The iron bacteria discovered by Ehrenberg in 1838 obtain their energy from the oxidation of iron compounds, the insolu- ble oxide remaining stored in the cell and accumulating into iron as the bacteria die.t_ In general the beds of iron ore found in certain of the pre-Cambrian stratified rocks, which have an estimated age of 60,000,000 years, are believed to be of bac- terial origin. Sulphur bacteria similarly obtain their energy from the oxidation of hydrogen sulphide. BACTERIA IN THE =BALANCE ZOE LIFE Bacteria thus anticipate the plant world of alge, diatoms, and carbon-formers, as well as the animal world of Protozoa and Mollusca, by playing an important réle in the formation of the new crust of the earth. This is observed in the primor- dial limestone depositions composed of calcium carbonate formed by bacterial action on the various soluble salts of cal- cium present in solution in sea-water, a process exemplified to-day” in the Great Bahama Banks, where chalk mud is now precipitated through accumulation by B. calcis. Doubtless in the shallow continental seas of the primal earth such bacteria swarmed, as in the shallow coastal seas of to-day, having both the power of secreting and precipitating lime and, at the same ‘It is claimed that iron bacteria play an important part in the formation of numerous small deposits of bog-iron ore, and it seems possible that their activities may be respon- sible for extensive sedimentary deposits as well. Further, the fact of finding iron bac- teria in underground mines opens the possibility that certain underground deposits of Iron ore may have been formed by them.—Harder, E. C., 1915, p. 311. * Drew, George H., 1914, p. 44. PROTOPLASM AND CHROMATIN on time, of converting nitrogen combinations. In the warm oceanic waters the amount of lime deposited is larger and the variety of living forms is greater; but the number of living forms which depend for food on the alge is less because the denitrify- ing bacteria which flourish in warm tropical waters deprive the algee of the nitrates so necessary for their development. Again, where algal growth is scarce, the protozoic unicellular and multicellular life (plankton) of the sea, which lives upon the alge, is also less abundant. This affords an excellent illustra- tion of the great law of the balance of the life environment through the equilibrium of supply of energy, one aspect of the interaction of organisms with their life environment. The denitrifying bacteria rob the waters of the energy needed for the lowest forms of plants, and these in turn are not available for the lowest forms of animal life. Thus in the colder waters of the oceans, where the denitrifying bacteria do not exist, the num- ber of living forms is far greater, although their variety is far less. ! The so-called luminous bacteria also anticipate the plants and animals in light production,” which is believed to be con- nected with the oxidation of a phosphorescing substance in the presence of water and of free oxygen. EVOLUTION OF PROTOPLASM AND CHROMATIN, THE Two STRUCTURAL COMPONENTS OF THE LIVING WORLD It is still a matter of discussion® whether any bacteria, even at the present time, have reached the evolutionary stage of the typical cell with its cell-wall, its contained protoplasm, and its distinct nuclear form and inner substance known as chro- matin. Some bacteriologists (Fischer) maintain that bacteria 1 Pirsson, Louis V., and Schuchert, Charles, 1915, p. 104. 2 Harvey, E. Newton, 1915, pp. 230, 238. 41 J. Kligler, Q2 THE ORIGIN AND EVOLUTION OF LIFE have neither nucleus nor chromatin; others admit the presence of chromatin, but deny the existence of a formal nucleus; others contend that the entire bacterial cell has a chromatin content; while still others claim the presence of a distinctly differenti- ated nucleus containing chromatin. Most of them, however, are agreed as to the presence in bacteria of granules of a chro- matin nature, while they leave as an open question the pres- ence or absence of a structurally distinct nucleus. This con- servative point of view is borne out by the fact that all the common bacteria have been found to contain nuclein, the spe- cific nuclear protein complex. Nucle1 and chromatin were ascribed to the Cyanophycee, by Kohl! as early as 1903 and by Phillips? and by Olive® in 1904. It is also a matter of controversy among bacteriologists whether protoplasm or chromatin is the more ancient. Cell observers (Boveri, Wilson, Minchin), however, are thoroughly agreed on this point. Thus Minchin is unable to accept any theory of the evolution of the earliest forms of living beings which assumes the existence of forms of life composed entirely of protoplasm without chromatin.‘ All the results of modern investigations—the combined results, that is to say, of cytology and protistology—appear to him to indicate that the chroma- tin elements represent the primary and original living units or individuals, and that the protoplasm represents a secondary product. As to whether chromatin or protoplasm is the more ancient, Boveri suggests that true cells arose through sym- biosis between protoplasm and chromatin, and that the chro- matin elements were primitively independent, living symbioti- cally with protoplasm. The more probable view is that of Wilson, that chromatin and protoplasm are coexistent in cells LRohL ehecG vino s 2 Phillips, O. P., 1904. 3 Olive, E. W., 1904. ‘ Minchin, E. A., 1916, p. 32. PROTOPLASM AND CHROMATIN 93 from the earliest known stages, in the bacteria and even prob- ably in the ultramicroscopic forms. The development of the cell theory after its enunciation in 1838 by Schleiden and Schwann followed first the differentia- Fic. 12. PROTOPLASM (GRAY) AND CHROMATIN (BLACK) OF Ameba, A TYPICAL PROTOZOAN. A group of six specimens of Amaba limax magnified tooo diameters; p=protoplasm; chr.=chromatin substance of nucleus; v=vacuoles. tand 5. Two amcebe with the chromatin nucleus (chr.) in the ‘“‘resting stage.” 2. An amoeba with the chromatin nucleus dividing into two chromatin nuclei. 3. A parent amoeba with chromatin nuclei completely separated. 4. Protoplasm and chromatin nuclei separated to form two young amcebe. After a photograph by Gary N. Calkins. tion of protoplasmic structure in the cellular tissues (histology). Since 1880 it has taken a new direction in investigating the chemical and functional separation of the chromatin. As proto- plasm is now known to be the expression, so chromatin is now known to be the seat of heredity which Nageli (1884) was the first to discuss as having a physicochemical basis; the “idio- plasm” postulated in his theory being realized in the actual O4 THE ORIGIN AND EVOLUTION OF LIFE structure of the chromatin as developed in the researches of Hertwig, Strasburger, Kolliker, and Weismann, who indepen- dently and almost simultaneously (1884, 1885) were led to the conclusion that the nucleus of the cell contains the physical basis of inheritance and that the chroma- tin is its essential constituent.1. In the development from unicellular (Protozoa) into multicellular (Metazoa) organisms the chromatin is distributed through the nuclei to “all: the scellSsot sthesbody.=but Boveri has demonstrated that all the body-cells lose a portion of their chroma- tin and only the germ-cells retain the entire ancestral heritage. Chemically, the most characteristic peculiarity of chromatin (Fig. 13), as 1 Wilson, E. B., 1906, p. 403. Fic. 13. THE Two STRUCTURAL COMPONENTS OF THE LIVING WORLD. Protoplasm or cytoplasm represents the chief visible form or substance of the cell in the growing condition. Chro- matin is the chief visible centre of heredity; there are doubtless other visible and invisible centres of energy concerned in heredity. PROTOPLASM (grayish dotted areas) and CHROMATIN (black, waving rods, threads, crescents, and paired spindles) in single cells (A—C) and in clusters of cells (D, £). A. Achromatium, bacteria-like organisms with network of chromatin threads and dots. B, C. Single-cell eggs in the ovaries of a sea-urchin (resting stage), the chromatin concentrated into a small black sphere within the nucleolus (inner circle). D. Many cells in the root-tip of an onion. Chromatin (division stage) in black, wavy lines and threads. E. Many cells in the embryo of the giant redwood-tree of California. Chromatin (division stage) in black, waving rods, threads, crescents, and spindles. The cell boundaries in thin black lines and the dotted protoplasm are clearly shown. After Lawson. PROTOPLASM AND CHROMATIN 95 contrasted with protoplasm, is its phosphorus content.! It is also distinguished by a strong affinity for certain stains which cause its scattered or collected particles to appear intensely dark (Fig. 13, A—E). Nuclein, whichis probably identical with chromatin, is a complex albuminoid substance rich in phos- phorus. The chemical, or molecular and atomic, constitution of chromatin infinitely exceeds in complexity that of any other form of matter or energy known. As intimated above (pp. 6, 77), it not improbably contains undetected chemical elements. Ex- periments made by Oskar, Gunther, and Paula Hertwig (1911- 1914) resulted in the conclusion that in cells exposed to radium rays the seat of injury is chiefly, if not exclusively, in the chro- matin:? these experiments point also to the separate and dis- tinct chemical constitution of the chromatin. The principle formulated by Cuvier, that the distinctive property of life is the maintenance of the individual specific form throughout the incessant changes of matter which occur in the inflow and outflow of energy, acquires wider scope in the law of the continuity of the germ-plasm (7. e., chromatin) announced by Weismann in 1883, for it is in the heredity- chromatin® that the ideal form is not only preserved, but through subdivision carried into the germ-cells of all the present and succeeding generations. It would appear, according to this interpretation, that the continuity of life since it first appeared in Archeozoic time is the continuity of the physicochemical energies of the chroma- tin; the development of the individual life is an unfolding of the energies taken within the body under the directing agency 1 Minchin, E. A., 1916, pp. 18,19. 2 Richards, A., 1915, p. 201. 3 The term “ chromatin” or “ heredity-chromatin ” as here used is equivalent to the “serm-plasm” of Weismann or the “stirp” of Galton. It is the visible centre of the energy complex of heredity, the larger part of which is by its nature invisible. Chro- matin, although within our microscopic vision, is to be conceived as a gross manifesta- tion of the infinite energy complex of heredity, which is a cosmos in itself. Fic. 14. BuLk OF CHROMATIN IN SEQUOIA AND TRILLIUM COMPARED. Chromatin rods in an embryonic cell of the Sequoia compared with those in an embryonic cell of the small wood-plant known as the Trinity-flower (Trillium). The chromatin of Sequoia (Sc.), which cone all the characters, potential and casual, of the giant tree, is less in bulk than the chromatin of Trillium (Tc.). . S. Sequoia washingtonia, or gigantea, the Big Tree of California. The tree known as General Sherman, shown here, is 2793%5 feet high above ground, its largest circumference is 102# feet, and its greatest diameter is 363 feet. : : - : Sc. Part of the germ cell of the nearly allied species, Sequoia sempervirens, the redwood, with the darkly stained chromatin rods in the centre. About 1,000 times actual size. The redwood is but little inferior in size to the “Big Tree.’’ After Goodspeed. T. Trillium. , ; Tc. Part of the germ cell of Trillium sessile, showing the darkly stained chromatin rods in the same phase and with the same magnification as in the cell of Sequoia. After Goodspeed. 96 PROTOPLASM AND CHROMATIN 97 of the chromatin; and the evolution of life is essentially the evolution of the chromatin energies. It is in the inconceivable physicochemical complexity of the microscopic specks of chromatin that life presents its most marked contrast to any of the phenomena observed within the lifeless world. Although each organism has its specific constant in the cubic content of its chromatin, the bulk of this content bears little relation to the size of the individual. This is illustrated by a comparison of the chromatin content of the cell-nucleus of Trillium, a plant about sixteen inches high, with that of Sequoia sempervirens, the giant redwood-tree of California, which reaches a height of from 200 to 340 feet! and attains an age of several thousand years (Fig. 14); we observe that the chromatin bulk in Sequoia is apparently less than that in Trillium. The chromatin content of such a nucleus is measured by the bulk of the chromosome rods of which it is composed. In the sea-urchin the size of the sperm-nucleus, the most compact type of chromatin, has been estimated as about 1/100,000,000 of a cubic millimetre, or to cubic microns, in bulk.? Within such a chromatin bulk there is yet ample space for an incal- culable number of minute particles of matter. According to the figures given by Rutherford® in the first Hale Lecture the dia- meter of the sphere of action of an atom is about 1 /100,000,000 1 Jepson, Willis Linn, 1911, p. 23. 2 E. B. Wilson, letter of June 28, 1916. $ Jt is necessary, observes Rutherford, to be cautious in speaking of the diameter of an atom, for it is not at all certain that the actual atomic structure is nearly so extensive as the region through which the atomic forces are appreciable. The hydrogen atom is the lightest known to science, and the average diameter of an atom is about 1/100,000,000 of a centimetre; but the negatively charged particles known as electrons are about 1/1800 of the mass of the hydrogen atom. ... These particles travel with enormous velocities of from 10,000 to 100,000 miles a second. ... The alpha particles produce from the neutral molecules a large number of negatively charged particles called ions. The ioniza- tion due to these alpha particles is measurable. . . . In the phosphorescence of an emanation of pure radium the atoms throw off the alpha particles with velocities of 10,000 miles a second, and each second five billion alpha particles are projected.—Ruth- erford, Sir Ernest, 1915, pp. 113, 128. 98 THE ORIGIN AND EVOLUTION OF LIFE of a centimetre, or 1/10,000,000 of a millimetre, or 1/10,000 of a micron—the unit of microscopic measurement. ‘The elec- trons released from atoms of matter are only 1/1800 of the mass of the hydrogen atom, the lightest known to science, and thus the mass of an electron would be only 1/18,000,000 of a micron. These figures help us in some measure to conceive of the chromatin as a microcosm made up of an almost unlimited number of mutually acting, reacting, and interacting particles; but while we know the heredity-chromatin to be the physical basis of inheritance and the presiding genius of all phases of development, we cannot form the slightest conception of the mode in which the chromatin speck of the germ cell controls the destinies of Sequoia gigantea and lays down all the laws of its being for its long life period of five thousand years. In observing the trunk of ‘‘General Sherman” (Fig. 14), the largest and oldest living thing known, one finds that an active regeneration of the bark and woody layers is still in progress, tending to heal scars caused by fire many centuries ago. This regeneration is attributable to the action of the heredity- chromatin in the plant tissues. We are equally ignorant as to how the chromatin responds to the actions, reactions, and interactions of the body cells, of the life environment, and of the physical environment, so as to call forth a new adaptive character,'! unless it be through some infinitely complex system of chemical messengers and other catalytic agencies (p. 77). Yet in pursuing the history of the evolution of life upon the earth we may constantly keep before us our fundamental biologic law? that the causes of evolution are to be sought within four complexes of energies, which are partly visible and partly invisible, namely: 1 Wilson, E. B., 1906, p. 434. 2 Osborn, H. F., 1912.2. CHLOROPHYLL 99 1. Physicochemical energies in the evo- lution of the physical environ- ment: Selection and Elimination 2. Physicochemical energies in the in- | Incessant competition, selection, dividual development of the or- | intraselection (Roux), and elim- ganism, namely, of its protoplasm ination between all parts of or- controlled and directed by its ganisms in their chromatin ener- chromatin; gies, in their protoplasmic ener- 3. Physicochemical energies in the evo- gies, and in their actions, reac- lution of the heredity-chromatin tions, and interactions with the with its constant addition of new living environment and with the powers and energies; physical environment. 4. Physicochemical energies in the evo- lution of the life environment, beginning with the protocellular chemical organisms, and such in- termediate organisms as bacteria, and followed by such cellular and multicellular organisms as_ the higher plants and animals. CHLOROPHYLL AND THE ENERGY OF SUNLIGHT As bacteria seek their energy in the geosphere and hydro- sphere, chlorophyll is the agent which connects life with the atmosphere, disrupting and collecting the carbon from its union with oxygen in carbon dioxide. The utilization of the energy of sunlight in the capture of carbon from the atmosphere through the agency of chlorophyll in alge marked the second great phase in the evolution of life, following the first bacterial phase. This capture of atmospheric carbon, the chief energy element of plants, always takes place in the presence of sun- light; while the chief energy elements of bacteria, nitrogen and (less frequently) carbon, are captured through molecule-splitting ~ in the presence of heat, but without the powerful aid of sun- light. It is the metamorphosed, fossilized tissue of plants which leads us to the conclusion that the agency of chlorophyll is I0O THE ORIGIN AND EVOLUTION OF LIFE also extremely ancient. Near the base of the Archean rocks! graphites, possibly formed from fossilized plant tissue, are observed in the Grenville series and in the Adirondacks. The very oldest metamorphosed sedimentaries are mainly composed of shales containing carbon which may have been deposited by plants. As a reservoir of life energy which is liberated by oxidation, hydrogen exceeds any other element. in the heat it yields, namely, 34.5 calories per gram, while carbon yields 8.1 calories per gram.? Since the carbohydrates constitute the basal energy-supply of the entire plant and animal world,* we may, with reference to the laws of action and reaction, examine the process even more closely than we have done above (p. 51). The results of the most recent researches are presented by Wager:? “The plant organ responds to the directive influence of light by a curvature which places it either in a direct line with the rays of light, as in grass seedlings, or at right angles to the light, as in ordinary foliage leaves.” “Of the light that falls upon a green leaf a part is reflected from its surface, a part is transmitted, and another part is absorbed. That which is reflected and transmitted gives to the leaf its green color; that which is absorbed, consisting of certain red, blue, and violet rays, 1s the source of the energy by means of which the leaf is enabled to carry on its work. ‘The extraordinary molecular complexity of chlorophyll has recently been made clear to us by the researches of Willstatter and his pupils; Usher and Priestley and others have shown us something of what takes place in chlorophyll when light acts upon it; and we are now beginning to realize more fully what a very complex photosensitive system the chlorophyll must 1 Pirsson, Louis V., and Schuchert, Charles, 1915, p. 545. * Henderson, Lawrence J., 1913, p. 245. “Moore, *i.).;«10 85D: alse ‘Wager, Harold, 1915, p. 468. EVOLUTION OF ALG IOI be, and how much has yet to be accomplished before we can picture to our minds with any degree of certainty the changes that take place when light is absorbed by it. But the evidence afforded by the action of light upon other organic compounds, especially those which, like chlorophyll, are fluorescent, and the conclusion according to modern physics teaching that we may regard it as practically certain that the first stage in any photochemical reaction consists in the separation, either par- tial or complete, of negative electrons under the influence of light, leads us to conjecture that, when absorbed by chloro- phyll, the energy of the light-waves becomes transformed into the energy of electrified particles, and that this initiates a whole train of chemical reactions resulting in the building up of the complex organic molecules which are the ultimate products of the plant’s activity.” Chlorophyll absorbs most vigorously the rays between B and C of the solar spectrum,! which are the most energizing; the effect of the rays between D and £ is minimal; while the rays beyond F again become effective. As compared with the primitive bacteria in which nitrogen figures so largely, chloro- phyllic plant tissues consist chiefly of carbon, hydrogen, and oxygen, the chief substance being cellulose (CsHO;),? while in some cases small amounts of nitrogen are found, and also min- eral substances—potassium, magnesium, phosphorus, sulphur, and manganese. Chlorophyllic algal life is thus in contrast with bacterial life, the prime function of which is to capture nitrogen. EVOLUTION OF THE ALGE Closest to the bacteria in their visible structure are the so- called “blue-green alge’’ or Cyanophycee, found almost every- 1 Loeb, Jacques, 1906, p. IIS. 2 Pirsson, Louis V., and Schuchert, Charles, 1915, p. 164. 102 THE ORIGIN AND EVOLUTION OF LIFE where in fresh and salt water and even in hot springs, as well as on damp soil, rocks, and bark. The characteristic color of the Red Sea is due to a free-floating form of these blue-green alge, which in this case are red. | Wnlikes thesstruc alge, the cell-nucleus of the Cyanophycee or- dinarily is not sharply limited by a membrane, and there is no evidence of distinct chlorophyll bodies, although chloro- phyll is present. In the simpler of the unicel- lular Cyanophycee the only method of repro- duction is that known as vegetative multipli- Fic. 15. _ Fosstt AnD LIVING ALG COMPARED C. A living algal pool colony near the Great Fountain Geyser, Yellowstone Park. After Walcott. B. Fossil calcareous alge, Crypto- zoon proliferum Hall, from the Cryptozoon Ledge in Lester Park near Saratoga Springs, N. Y. These alge, which are among the oldest plants of the earth, grew in cabbage-shaped heads on the bottom of the ancient Cambrian sea and deposited lime in their tissue. The ledge has been planed down by the action of a great glacier which cut the plants across, showing their concentric interior structure. Photographed by H. P. Cushing. A. Fossil alge, Newlandia concentrica, Newlandia frondosa, from the Algonkian Belt Series of Montana. After Walcott. EVOLUTION OF ALG: 103 cation, in which an ordinary working cell (individual) divides to form two new individuals. In certain of the higher forms, in which there is some differentiation of connected cells and in which we seem justified in considering the “ individual”’ to be multicellular, multiplication is accomplished through the agency of cells of special character known as the spores. No evidences of sexual reproduction have been observed in the Cyanophycee. The sinter deposits of hot springs and geysers in Yellowstone Park are attributed to the presence of Cyanophycee.! With the appearance of the true alge the earth-forming powers of life become still more manifest, and few geologic discoveries of recent times are more important than those growing out of the recognition of alge as earth-forming agents. As early as 1831 Lyell remarked their rock-forming powers. It is now known that there are formations in which the alge rank first among the various lower organisms concerned in earth-building. In a forthcoming work by F. W. Clarke and W. C. Wheeler, they remark upon these earth-building activ- ities as follows: “The calcareous alge are so important as reef-builders that, although they are not marine invertebrates in the ordinary acceptance of the term, it seemed eminently proper to include them in this investigation. In many cases they far outrank the corals in importance, and of late years much attention has been paid to them. On the atoll of Funa- futi, for example, the alge Lithothamnium and Halimeda rank first and second in importance, followed by the foraminifera, third, and the corals, fourth.’’ Algze are probably responsible for the formation of the very ancient limestones; those of the Grenville series at the very base of the pre-Cambrian are believed to be over 60,000,- 000 years of age. The algal flora of the relatively recent Al- 1 Coulter, John Merle, 1910, pp. 10-14. 104 THE ORIGIN AND EVOLUTION OF LIFE gonkian time,’ together with calcareous bacteria, developed the massive limestones of the Tetons. Clarke observes: ‘We are now beginning to see where the magnesia of the limestones comes from and the alge are probably the most important contributors of that constituent.”’ Thus representatives of the Rhodophycez contribute as high as 87 per cent of calcium carbonate and 25 per cent of magnesium carbonate. Species of Halimeda, however, calci- fied alge belonging to the very different class Chlorophycee, are important agents in reef-building and land-forming, yet are almost non-magnesian.’ The Grenville series at the base of the Paleozoic is essen- tially calcareous, with a thickness of over 94,000 feet, nearly eighteen miles, more than half of which is calcareous.* Thus it appears probable that the surface of the primordial conti- nental seas swarmed with these minute alge, which served as the chief food magazine for the floating Protozoa; but it is very important to note that algal life is absolutely dependent upon phosphorus and other earth-borne constituents of sea-water, as well as upon nitrogen, also earth-borne, and due to bacterial action; for where the denitrifying bacteria rob the sea-water of its nitrogen content the alge are much less numerous.‘ Silica is also an earth-borne, though mineral, constituent of sea-water which forms the principal skeletal constituent of the shells of diatoms, minute floating plants especially charac- teristic of the cooler seas, which form the siliceous ooze of the sea-bottoms. ‘Walcott, Charles D., 1914. 2M. A. Howe, letter of February 24, 1916. * Pirsson, Louis V., and Schuchert, Charles, 1915, pp. 545, 546. 50D. Cit, DvtOAs PLANT AND ANIMAL EVOLUTION 105 SOME PHYSICOCHEMICAL CONTRASTS BETWEEN PLANT AND ANIMAL EVOLUTION In their evolution, while there is a continuous specialization and differentiation of the modes of obtaining energy, plants may not attain a higher chemical stage than that observed among the bacteria and alge, except in the parasitic forms which feed both upon plant and animal compounds. In the energy which they derive from the soil plants continue to be closely dependent upon bacteria, because they derive their nitrogen from nitrates generated by bacteria and absorbed along with water by the roots. In reaching out into the air and sunlight the chlorophyllic organs differentiate into the marvellous variety of leaf forms, and these in turn are sup- ported upon stems and branches which finally lead into the creation of woody tissues and the clothing of the earth with forests. Through the specialization of leaves in connection with the germ-cells flowers are developed, and plants establish a marvellous series of balanced relations with their life environ- ment, first with the developing insect life, and finally with the developing bird life. The main lines of the ascent and classification of plants are traced by paleobotanists partly from their structural evolu- tion, which is almost invariably adapted to keep their chloro- phyllic organs in the sunlight! in competition with other plants, and partly from the evolution of their reproductive organs, which pass through the primitive spore stage into various forms of sexuality, with, finally, the development of the seed habit and the dominance of the sporophyte.? It is a striking peculiarity of plants that the powers of motion evolve chiefly in connection with their reproductive activities, namely, with 1 Wager, Harold, 1915, p. 468. 2M. A. Howe. 106 THE ORIGIN AND EVOLUTION OF LIFE the movements of the germ cells. We follow the development of a great variety of automatic migrating organs, especially in the seed and embryonic stages, by which the germs, or chro- matin bearers, are mechanically propelled through the air or water. Plants are otherwise dependent on the motion of the atmosphere and of animals to which they become attached for the migration of their germs and embryos and of their adult forms into favorable conditions of environment. In these respects and in their fundamentally different sources of energy they present the widest contrast to animal evolution. In the absence of a nervous system the remarkable actions and reactions to environmental stimuli which plants exhibit are purely of a physicochemical nature. The interactions be- tween different tissues of plants, which become extraordinarily complex in the higher and larger forms, are probably sustained through catalysis and the circulation through the tissues of chemical messengers analogous to the enzymes, hormones (ac- celerators), and chalones (retarders) of the animal circulation. It is a very striking feature of plant development and evolu- tion that, although entirely without the coordinating agency of a nervous system, all parts are kept in a condition of perfect correlation. This fact is consistent with the comparatively © recent discovery that a large part of the coordination of animal organs and tissues which was formerly attributed to the ner- vous system is now known to be catalytic. Throughout the evolution of plants the fundamental dis- tinctions between the heredity-chromatin and the body-proto- plasm are sustained exactly as among animals. It would appear from the researches of de Vries! and other botanists that the sudden hereditary alterations of plant struc- ture and function which may be known as mutations of de 1 De Vries, Hugo, 1901, 1903, 1905. PLANT AND ANIMAL EVOLUTION 107 Vries‘ are of more general occurrence among plants than among animals. Such mutations are attributable to sudden alterations of molecular and atomic constitution in the hered- ity-chromatin, or to the altered forms of energy supplied to the chromatin during development. Sensitiveness to the bio- chemical reactions of the physical environment should theo- retically be more evident in organisms like plants which derive their energy directly from inorganic compounds that are con- stantly changing their chemical formule with the conditions of moisture, of aridity, of temperature, of chemical soil con- tent, than in organisms like animals which secure their food compounds ready-made by the plants and possessing com- paratively similar and stable chemical formule. Thus a plant transferred from one environment to another may exhibit much more sudden and profound changes than an animal, for the reason that all the sources of plant energy are profoundly changed while the sources of animal energy in a new environ- ment are only slightly changed. The highly varied chemical sources of plant energy are in striking contrast with the com- paratively uniform sources of animal energy which are primarily the starches, sugars, and proteins formed by the plants. In respect to character origin, or the appearance of new characters, therefore, plants may in accordance with the de Vries mutation hypothesis exhibit discontinuity or sudden changes of form and function more frequently than animals. In respect to character coordination, or the harmonious relations of all their parts, plants are inferior to animals only in their sole dependence on catalytic chemical messengers, while animal characters are coordinated both through catalytic chemical messengers and through the nervous system. In respect to character velocity, or the relative rates of move- 1 As distinguished from the earlier defined Mutations of Waagen (see p. 138). 108 THE ORIGIN AND EVOLUTION OF LIFE ment of different parts of plants in individual development and in evolution, plants appear to agree very closely with animals. In both we observe that some characters evolve more rapidly or more slowly than others in geologic time; also that some characters develop more rapidly or slowly than others in the course of individual growth. This may be termed charac- ter motion or character velocity. This law of changes in character velocity, both in individ- ual development (ontogeny) and in racial evolution (phylog- eny), is one of the most mysterious and difficult to understand in the whole order of biologic phenomena. One character is hurried forward so that it appears in earlier and earlier stages of individual development (Hyatt’s law of acceleration), while another is held back so that it appears in later and later stages (Hyatt’s law of retardation). Osborn has also pointed out that corresponding characters have different velocities in different lines of descent—a character may evolve very rapidly in one line and very slowly in another. ‘This is distinctively a heredity-chromatin phenomenon, although visible in protoplas- mic form. Among plants it is illustrated by the recent obser- vations of Coulter on the relative time of appearance of the archegonia in the two great groups of gymnosperms (i. e., naked-seeded plants), the Cycads (sago-palms, etc.) and the Conifers (pines, spruces, etc.), as follows: In the Cycads, which are confined to warmer climates, the belated appearance of the archegonium persists; in the Conifers, in adaptation to colder climates and the shortened reproductive season, the appearance of the archegonium is thrust forward into the early embryonic stages. Finally, in the flowering plants (Angiosperms) with their brief reproductive season, the forward movement of the archegonium continues until the third cellular stage of the em- bryo is reached. This is but one illustration among hundreds PLANT AND ANIMAL EVOLUTION 109g which might be chosen to show how character velocity in plants follows exactly the same laws as in animals, namely, characters are accelerated or retarded in race evolution and in individual development in adaptation to the environmental and individual needs of the organism. We shall see this mysterious law of character velocity beautifully illustrated among the vertebrates, where of two characters, lying side by side, one exhibits inertia, the other momentum. It is difficult to resist the speculation that character velocity in individual development and in evolution is also a phenom- enon of physicochemical interaction in some way connected with and under the control of chemical messengers which are circulating in the system. PART oll.) THESE VOLU PONG @TaeAINUV UAL @) rey Ciabavedhisice (hy THE ORIGINS OF ANIMAL LIFE AND EVOLUTION OF THE INVERTEBRATES Evolution of single-celled animals or Protozoa. Evolution of many-celled animals or Metazoa. Pre-Cambrian and Cambrian forms of Inverte- brates. Reactions to climatic and other environmental changes of geo- logic time. The mutations of Waagen. A prime biochemical characteristic in the origin of animal life is the derivation of energy neither directly from the water, from the earth, nor from the earth’s or sun’s heat, as in the most primitive bacterial stages; nor from sunshine, as in the chlorophyllic stage of plant life; but from its stored form in the bacterial and plant world. All animal life 1s chemically dependent upon bacterial and plant life. Many of the single-celled animals like the single-celled bac- terla and plants appear to act, react, and interact directly with their lifeless and life environment, their protoplasm be- ing relatively so simple. We do not know how far this action, reaction, and interaction affects the protoplasm only, and how far it affects both protoplasm and chromatin. It would seem as if even at this early stage of evolution the organism-proto- plasm was sensitive while the heredity-chromatin was relatively insensitive to environment, stable, and as capable of conserving and reproducing hereditary characters true to type as in the many-celled animals in which the heredity-chromatin is deeply buried within the tissues of the organism remote from direct environmental reactions. EVOLUTION OF PROTOZOA — III EVOLUTION OF SINGLE-CELLED ANIMALS OR PROTOZOA We have no idea when the first unicellular animals known as Protozoa appeared. Since the Protozoa feed freely upon bacteria, it is possible they may have evolved during the bac- terial epoch; it is known that Protozoa are at present one of the limiting factors of bacterial activity in the soil, and it is even claimed! that they have a material effect on the fertility of the soil through the consumption of nitrifying bacteria. On the other hand, it may be that the Protozoa appeared during the algal epoch or subsequent to the chlorophyllic plant organisms which now form the primary food supply of the freely floating and swimming protozoan types. A great num- ber of primitive flagellates are saprophytic, using only dis- solved proteids as food.’ Apart from the parasitic mode of deriving their energy, even the lowest forms of animal life are distinguished both in the embryonic and adult stages by their locomotive powers. Heliotropic or sun reactions, or movements toward sunlight, are manifested at an early stage of animal evolution. In this function there appear to be no boundaries between animals and the motile spores, gametes, and seedlings of certain plants.* As cited by Loeb and Wasteneys, Paul Bert in 1869 discovered that the little water-flea Daphnia swims toward the light in all parts of the visible spectrum, but most rapidly in the yellow or in the green. More definitely, Loeb observes that there are two particular regions of the spectrum, the rays of which are especially effective in causing organisms to turn, or to congre- gate, toward them; these regions lie (1) in the blue, in the 1 Russell, Edward John, and Hutchinson, Henry Brougham, 1909, p. 118; 1913, pp. TOI, 210. 2 Gary N. Calkins. 3 Loeb, Jacques, and Wasteneys, Hardolph, 1915.1, pp. 44-47; 1915.2, pp. 328-330. Vea eeee fo, oh Jd By em ed ME, ORY s Fic. 16. TyprcAaL Forms oF PROTOZOA OR SINGLE-CELLED ORGANISMS. A. Ameba proteus, one of the soft, unprotected, jelly-like organisms which rank among the simplest known animals. They are continually changing form by thrusting out or withdrawing the lobe-like projections known as pseudopodia, which are temporary prolongations of the cell-body for purposes of locomotion or food capture. Any part of the body may serve for the purpose of food ingestion, which is accomplished by simply extending the body so as to surround the food. Magnified 200 times life-size. After Leidy. D. A colony of flagellates or Mastigophora, showing a number of individuals in various stages of their life his- tory. They are distinguished by one or more whip-like prolongations which serve chiefly for purposes of locomotion. As contrasted with the Amaba, many of the flagellates have definite, characteristic body forms, and have the function of food ingestion limited to a special area of the body. Magnified 285 times life-size. Photographed from a model in the American Museum. E. A typical ciliate, one of the most highly organized single-celled forms, distinguished by a multitude of fine hair-like cilia, distributed over the whole or a part of the body, which are used for locomotion and for the capture of food. In some forms these cilia are grouped or specialized for further effectiveness. After Biitschli Magnified 180 times life-size. II2 EVOLUTION OF PROTOZOA II3 neighborhood of a wave-length of 477 pu, and (2) in the yellowish-green, in the region of A == 534 mu; and these two wave-lengths affect different organisms, with no very evident relation to the nature of these latter. Thus the blue rays (of 477 mu) attract the protozoan flagellate Euglena, the hydroid AP eer LLY ULTRA VIOLET Fic. 17. Licut, HEAT, AND CHEMICAL INFLUENCE OF THE SUN. Diagram showing the increase, maximum, and decrease of heat, light, and chemical energy derived from the sun. The shaded area represents that portion of the spec- trum included in the phosphorescent light emitted by our common fire-flies. It is probable that it corresponds more closely with the light sensitiveness of the fire-fly’s eye than with that of the human eye as represented by the wave marked “Light.” After Ulric Dahlgren. ceelenterate Hudendrium, and the seedlings of oats; while the yellowish-green rays (of 534 mu) in turn affect the protozoan Chlamydomonas, the crustacean Daphnia, and the crustacean larve of barnacles. Aside from these heliotropic movements which they share with plants, animals show higher powers of individuality, of initiation, of experiment, and of what Jennings cautiously terms ‘‘a conscious aspect of behavior.’? In his remarkable studies this author traces the genesis of animal behavior to (Rah THE ORIGIN AND EVOLUTION OF LIFE ‘reaction and trial. Thus the behavior of organisms is of such a character as to provide for its own development. Through the principle of the production of varied movements and that of the resolution of one physiological state into another, any- thing that is possible is tried and anything that turns out to be advantageous is held and made permanent.! Thus the sub- psychic stages when they evolve into the higher stages give us the rudiments of discrimination, of choice, of attention, of desire for food, of sensitiveness to pain, and also give us the foundation of the psychic properties of habit, of memory, and of consciousness.2 These profound and extremely ancient powers of animal life exert indirectly a creative influence on animal form, whether we adopt the Lamarckian or Darwinian explanation of the origin of animal form, or find elements of truth in both explanations.’ The reason is that choice, dis- crimination, attention, desire for food, and other psychic powers are constantly acting on individual development and directing its course. Such action in turn controls the habits and migrations of animals, which finally influence the laws of adaptive radiation’ and of selection. In this indirect way these psychic powers are creative of new form and new function. In the evolution of the Protozoa® the starting-point is a simple cell consisting of a small mass of protoplasm contain- ing a nucleus within which lies the heredity-chromatin (Fig. 12). This passes into the plasmodial condition of the Rhizopods, in which the protoplasm increases enormously to form the relatively large, unprotected masses adapted to 1 Jennings, H. S., 1906, pp. 318, 310. 2 OP. cit., pp. 320-335. _ * These two explanations are fully set forth below (see pp. 143-146) in the introduc- tion to the evolution of the vertebrates. * Adaptive radiation—the development of widely divergent forms in animals ances- trally of the same stock or of related stocks, as a result of bodily adaptation to widely different environments (see p. 157). ® Minchin, E. A., 1916, p. 277. EVOLUTION OF PROTOZOA IIS the creeping or semiterrestrial mode of life. From _ these evolve the forms specialized for the floating pelagic habit, namely, the Foraminifera and Radiolaria, protected by an excessive development and elaboration of their skeletal struc- tures.1 Less cautious observers? than Jennings find in the Fic. 18. SKELETONS OF TYPICAL PROTOZOA. B. Siliceous skeleton or shell of a typical radiolarian, Stauraspis stauracantha Haeckel, 170 times the actual size. Owing to their vast numbers, these microscopic, glassy skeletons are an appreciable factor in earth-building. A large part of the island of Barbados is formed of radiolarian ooze. Photographed from a model in the American Museum. C. Calcareous skeleton or shell of a typical foraminifer, Globigerina bulloides d’Orbigny, 30 times the actual size. As the animal increases in size it forms successively larger shells adjoining the earlier ones until, as shown in the figure, a cluster of shells of increasing size is formed. The name foraminifer refers to the many minute openings, plainly seen in this figure, through which the pseudopodia can pass. Photographed from a model in the American Museum. (Compare Fig. 16, Dp, TT2:) Foraminifera the rudiments of the highest functions and the most intelligent behavior of which undifferentiated protoplasm has been found capable. In the Mastigophora the body de- velops flagellate organs of locomotion and food-capture. As an offshoot from the ancestors of these forms arose the Czlzata, the most highly organized unicellular types of living beings, 1 Op. cit., p. 278: 2 Heron-Allen, Edward, 1915, p. 270. 116 THE ORIGIN AND EVOLUTION OF LIFE for a Ciliate, like every other protozoan, is a complete and independent organism, and is specialized for each and all of the vital functions performed by the higher multicellular or- ganisms as a whole. In the chemical life of the Protozoa! (Ameba) the proto- plasm is made up of colloidal and of crystalloidal substances of different density, between which there is a constant, orderly chemical activity. The relative speed of these orderly proc- esses is attributed to specific catalyzers which control each successive step in the long chain of chemical actions. Thus in the breaking-down process (destructive metabolism) the by- products act as poisons to other organisms or they may play an important part in the vital activities of the organism itself, as in the phosphorescence of Noctiluca, or as in reproduction and regeneration. Since regrowth or regeneration’ takes place in artificially separated fragments of cells in which the nuclear substance (chromatin) is believed to be absent, the formation of new parts may be due to a specific enzyme, or perhaps to some chemical body analogous to hormones and formed as a result of mutual interaction of the nucleus and the protoplasm. Reproduction through cell-division is also interpreted theoreti- cally as due to action set up by enzymes or other chemical bodies produced as a result of interaction between the nucleus and cell body. The protoplasm is regenerated, including both the nuclei and the cell-plasm, by the distribution of large quan- tities of nucleoproteins, the specific chemical substance of chromatin. The latest word as to the part played by natural selection in the heredity-chromatin is that of Jennings’ who, after many years of experiment, has proved that the congenital charac- 1 Calkins, Gary N., 1916, p. 260. 2 Op. cit., pp. 261-264, 266. 3 Jennings, H. S., 1916, pp. 522-526. EVOLUTION OF METAZOA D7 ters arising from the heredity-chromatin are changed by long- continued selection through a great number of generations in the form of slow gradations which would not be revealed by imperfect selection for a few generations. This is doubtless the way in which nature works. In the protozoan known as Diffiugia the inherited changes produced by selection seem as gradual as could well be observed. Large steps do occur, but much more frequent is the slow alteration of the stock with the passage of generations. The question is asked whether even such slight and seemingly gradual hereditary changes may not really be little jumps or mutations, since all chemical change is discontinuous. In reply, Jennings observes that it is highly probable that every inherited variation does involve a chemical change, for there is no character change so slight that it may not be chemical in nature. In the relatively immense organic molecule, with its thousands of groups, the simple trans- fer of one atom, one ion, perhaps one electron, 1s a chemical change and, in this sense, discontinuous even though its effect is below our powers of perception with the most refined instru- ments. Through this modern chemical interpretation of the pro- tozoan life cycle we may conceive how the laws of thermody- namics may be applied to single-celled organisms, and espe- cially our fundamental biologic law of action, reaction, and inter- action. By far the most difficult problem in biologic evolution is the mode of working of this law among the many-celled or- ganisms (Metazoa) including both invertebrates and vertebrates. EVOLUTION OF MANY-CELLED ANIMALS OR METAZOA It is possible that during the long period of pre-Cambrian time, which, from the actual thickness of the Canadian pre- Cambrian rocks, is estimated at not less than thirty million 118 THE ORIGIN AND EVOLUTION OF LIFE years, some of the simpler Protozoa gave rise to the next higher stage of animal evolution and to the adaptive radiation on land and sea of the Invertebrata. We are compelled to assume that the physicochemical actions, reactions, and interactions were sustained and became step by step more complex as the single-celled “ life forms (Protozoa) evolved into or- PHYLA, OF HOSSIE INVERTEBRATA ganisms with groups of cells (Metazoa), Protozoa, and these into organisms with two chief Porifera, cell-layers (Ccelenterata), and later = yp nn into organisms with three chief cell- Echinoderms em layers. Annulata, The metamorphosis by heat and Renee pressure of the pre-Cambrian rocks has for the most part concealed or destroyed all the life impressions which were undoubtedly made in the various continental or oceanic basins of sedimentation. Indirect evidences of the long process of life evolution are found in the great accumula- tions of limestone and in the deposits of iron and graphite! which, as we have already observed, are considered proofs of the existence at enormously remote periods of limestone- forming alge, of iron-forming bacteria, and of a variety of chlorophyll-bearing plants. These evidences begin with the metamorphosed sedimentaries overlying the basal rocks of the crust of the primal earth. PRE-CAMBRIAN AND CAMBRIAN FORMS OF INVERTEBRATES The discovery by Walcott? of a world of highly specialized and diversified invertebrate life in the Middle Cambrian seas completely confirms the prophecy made by Charles Darwin in ' Joseph Barrell. See Pirsson, Louis V., and Schuchert, Charles, 1915, p. 547. ? Walcott, Charles D., 1911, 1912. CAMBRIAN INVERTEBRATES II9Q 1859' as to the great duration that must be assigned to pre- Cambrian time to allow for the evolution of highly specialized life forms. | By Middle Cambrian time the adaptive radiation of the Invertebrata to all the conditions of life—in continental waters, BRIAN 5 130 ‘ tos 7S 60 3S, tO 165 PALEOGEOGRAPHY. LATE LOWER CAMBRIAN (WAUCOBIAN OR OLENELLUS) TIME AFTER SCHUCHERT, APRIL, 1916 SH wonine DEPOSITS or ACTIVE VOLCANOES IN SCOTLAND a MOUNTAINS A= ARCHAEOCYATHINAE Fic. 19. THEORETIC WORLD ENVIRONMENT IN LATE LOWER CAMBRIAN TIME. This period corresponds with that of the first well-known marine fauna with trilobites and brachiopods as the dominant forms. No land life of any kind is known, and the climate appears to have been warm and equable the world over. After Schuchert. along the shore-lines, and in the littoral and pelagic environ- ment of the seas—appears to have been governed by mechan- ical and chemical principles fundamentally similar to those observed among the Protozoa, but distributed through myriads of cells and highly complicated tissues and organs, instead of being differentiated within a single cell as in the ciliate Pro- tozoa. Among the elaborate functions thus evolved, showing 1 Darwin, Charles, 1850, pp. 306, 307. 120 THE ORIGIN AND EVOLUTION OF LIFE a more complicated system of action, reaction, and interaction with the environment and within the organism, were, first, a more efficient locomotion in the quest of food, in the capture of food, and in the escape from enemies, giving rise in some cases to skeletal structures of various types; second, the evolu- tion of offensive and defensive weapons and armature; third, various chemical modes of offense and defense; fourth, protec- tion and concealment by methods of burrowing.! There are heavy protective coverings for slowly moving and sessile animals. In contrast we find swiftly moving types (e. g., Sagitta and other chetognaths) with the lines of modern submarines, whose mechanical means of propulsion resemble those of the most primitive darting fishes. Other types, such as the Crustacea, have skeletal parts for the triple purposes of defense, offense, and locomotion, some being adapted to less swift motion. In Paleozoic time they include the slowly moving, bottom-living, armored types of trilobites. Then there are other slowly moving, bottom-living forms, such as the brachiopods and gastropods, with very dense armature of phosphate and carbonate of lime. Finally, there are pelagic or surface-floating types, such as the Jellyfishes, which are chemically protected by the poisonous secretions of their ‘sting-cells.”’ This highly varied life of mid-Cambrian time affords abun- dant evidence that in pre-Cambrian time certain of the inver- tebrates had already passed through first, second, and even third phases of form in adaptation to as many different life zones. Our first actual knowledge of such extremely ancient adap- tations dates back to the pre-Cambrian and is afforded by Wal- cott’s discovery? in the Greyson shales of the Algonkian Belt 1R. W. Miner. 2 Walcott, Charles D., 1899, pp. 235-244. CAMBRIAN INVERTEBRATES Meee Series of fragmentary remains of that problematic fossil, Bel- tina danat, which he refers to the Merostomata and near to the eurypterids, thus making it probable that either eurypterids, or forms ancestral both to trilobites and eurypterids existed in pre- Cambrian times. More extensive adaptive radiations are found in the Lower Cambrian life period of Olenellus. This trilobite is not primitive but a compound phase of evolution, and rep- resents the highest trilobite development. Trilobites TRILCOBITA | are beautifully preserved as fossils because of their dense chitinous armature, which protected them and at the same time admitted of con- siderable freedom of mo- tion. The relationships of the trilobites to other in- vertebrates have long been enue Serratus Oo Mid Ce metian 555 2 Fic. 20. A M1p-CAMBRIAN TRILOBITE. in dispute, but the dis- Neolenus serratus (Rominger). After Walcott. covery of the ventral sur- face and appendages in the mid-Cambrian WNeolenus serratus (Fig. 20) seems to place the trilobites definitely as a subclass of the Crustacea, with affinities to the freely swimming phy]l- lopods, which swarm on the surface of the existing oceans. A most significant biological fact is that certain of the primitively armored and sessile brachiopods of the Cambrian seas have remained almost unchanged generically for a period of nearly thirty million years, down to the present time. These animals afford a classic illustration of the rather exceptional condition known to evolutionists as “‘balance,’”’ resulting in absolute stability of type. One example is found in Lingulella (Lingula), of which the fossil form, Lingulella acuminata, char- 122 THE ORIGIN AND EVOLUTION OF LIFE acteristic of Cambrian and Ordovician times, is closely similar to that of Lingula anatina, a species living to-day. Represen- tatives of the genus Lingula (Lingulella) have persisted from Cambrian to Recent times. The great antiquity of the brachi- opods as a group is well illustrated by the persistence of Lingula (Cambrian—Ordovician—Recent), on the one hand, and of Terebratula (Devonian—Recent), belonging to a widely differ- ing family, on the other. These lamp-shells are thus charac- teristic of all geologic ages, including the present. Reaching their maximum radiation during the Ordovician and Silurian, they gradually lost their importance during the Devonian and Permian, and at the present time have dwindled into a rela- tively insignificant group, members of which range from the oceanic shore-line to the deep-sea or abyssal habitat. By the Middle Cambrian the continental seas covered the whole region of the present Cordilleras of the Pacific coast. In the present region of Mount Stephen, B. C., in the unusually favorable marine oily shales of the Burgess formation, the remarkable evolution of invertebrate life prior to Cambrian time has been revealed through Walcott’s epoch-making dis- coveries between 1909 and 1912.! It is at once evident (Figs. 20-27) that the seashore and pelagic life of this time exhibits types as widely divergent as those which now occur among the aquatic Invertebrata; in other words, the extremes of invertebrate evolution in the seas were reached some thirty million years ago. Not only are the characteristic external features of these soft-bodied invertebrates evident in the fossil remains, but in some cases (Fig. 22) even the internal organs show through the imprint of the transparent integument. Walcott’s researches on this superb series have brought out two important points: First, the great antiquity of the chief 1 Walcott, Charles D., 1911, 1912. CAMBRIAN INVERTEBRATES ee aquatic invertebrate groups and their high degree of special- ization in Early Cambrian times, which makes it necessary to look for their origin far back in the pre-Cambrian ages; and, second, the extraordinary persistence of type, not only among the lamp-shells (brachiopods) but among members of all the invertebrate phyla from the mid-Cambrian to the present -BRACHIOPODA : BRACHIOPODA Minguielia (Fossil) | Lin _ Lingulella ebratula “Cembrian Recent : Camby Whecan @ Camb-Recent Devon -Recent Fic. 21. BRACHTOPODS, CAMBRIAN AND RECENT. Lingulella (Lingula) acuminata, a fossil form ranging from Cambrian to Ordovician, and the very similar existing form, Linguwla anatina, which shows that the genus has persisted from Cambrian times down to the present day. Lingulella (fossil), Cambrian to Ordovician, contrasted with a living specimen of the widely differing Terebratula, which ranges from Devonian to recent times. time; so that sea forms with an antiquity estimated at tw enty- five million years can be placed side by side with existing sea forms with very obvious similarities of function and structure, as in the series arranged for these lectures by Mr. Roy W. Miner, of the American Museum of Natural History (Figs. 21, 22, 24-27). Except for the trilobites, the existence of Crustacea in Cambrian times was unknown until the discovery of the prim- 124 THE ORIGIN AND EVOLUTION OF LIFE itive shrimp-like form, Burgessia bella (Fig. 22), a true crusta- cean, which may be compared with Apus lucasanus, a mem- ber of the most nearly allied recent group. We observe a close correspondence in the shape of the chitinous shield (car- apace), in the arrangement of the leaf-like locomotor appen- dages at the base of the tail, and in the clear internal impres- CRUSTACEA Burgessis Sid. Cambrian Fic. 22. HorsESHOE CRAB AND SHRIMP, CAMBRIAN AND RECENT. Molaria spinifera, a mid-Cambrian merostome (after Walcott), compared with the recent ‘‘horseshoe crab,” Limulus polyphemus. Burgessia bella, a shrimp-like crustacean of the Middle Cambrian (after Walcott), compared with the very similar A pus lucasanus of recent times. sions in Surgessia of the so-called ‘‘kidneys,”’ with their branched tubules. The position of these organs in Apus is indicated by the two light areas on the carapace. Other specimens of Burgessia found by Walcott show that the taper- ing abdominal region and tail are jointed as in A pus. The age of the armored merostome arthropods is also thrust back to mid-Cambrian times by the discovery of several genera of Aglaspide, the typical species of which, Molaria spinifera Walcott, may be compared with that ‘‘living fossil,” CAMBRIAN INVERTEBRATES 125 the horseshoe crab (Limulus polyphemus), its nearest modern relative, which is believed to be not so closely related to the phyllopod crustaceans as would at first appear, but rather to the Arachnida through the eurypterids and scorpions. Mo- laria and Limulus are strikingly similar in their cephalic shield, — MIDDLE CAMBRIAN PALEOGEOGRAPHY, MIDDLE CAMBRIAN (ACADIAN OR PARADOXIDES) TIME AFTER SCHUCHERT, APRIL, 1916 JS MARINE DEPOSITS Fic. 23. THEORETIC WORLD ENVIRONMENT IN MIDDLE CAMBRIAN TIME. The period of the trilobite Paradoxides. This shows the theoretic South Atlantic con- tinent ‘‘Gondwana” of Suess, connecting Africa and South America. segmentation, and telson; but the latter shows an advance upon the earlier type in the coalescence of the abdominal seg- ments into a single abdominal shield-plate. The trilobate character of the cephalic shield in Molaria is an indication of its trilobite affinities; hence we apparently have good reason to refer both the merostomes and phyllopods to an ancestral trilobite stock. Another mode of defense is presented by some of the sessile, rock-clinging sea-cucumbers (Holothuroidea) protected 126 THE ORIGIN AND EVOLUTION OF LIFE not only by their habit of hiding in crevices, but by their leathery epidermis, in which are scattered a number of cal- careous plates, as among certain members of the modern eden- tate mammals. Fossils of this group have been known here- tofore only through scattered spicules and calcareous plates dating back no earlier than Carboniferous times (Goodrich) ; therefore Walcott’s holothurian material from the Cambrian constitutes new records for invertebrate paleontology, not only for the preservation of the soft parts, but for the great antiquity of these Cambrian strata. In Lowisella pedunculata (Fig. 24) we observe the preservation of a double row of tube- feet, and the indication at the top of oral tentacles around the mouth like those of the modern Elpidiide. A typical rock- clinging holothurian is the recent Pentacta frondosa. Besides these sessile, rock-clinging forms, the adaptive radiation of the holothurians developed burrowing or fossorial types, an example of which is the mid-Cambrian Mackenzia costalis (Fig. 24) which strikingly suggests one of the existing burrowing sea-cucumbers, Synapta girardu. The character- istic elongated cylindrical body-form with longitudinal muscle- bands is clearly preserved in the fossil, while around the mouth is a ring of tubercles interpreted by Walcott as calcareous ossicles from above which the oral tentacles have been torn away. A remarkable and problematic mid-Cambrian fossil, Eldonia ludwigi (Fig. 24), is regarded by Walcott as a free-swimming or pelagic animal. It bears a superficial resemblance to a medusa, or jellyfish, while the lines radiating from a central ring suggest the existence of a water vascular system; but the cylindrical body coiled around the centre shows a spiral intes- tine through its transparent body-wall, and it is therefore con- sidered to be a swimming holothurian, or sea-cucumber, with CAMBRIAN INVERTEBRATES B27, a medusa-like umbrella. The existing holothuroid Pelagothuria natatrix Ludwig, shown at the right, is somewhat analogous, HOLOTHUROIDEA Etdonis Mid Cambrian HOLOTHUROIDEA Mid. Cambrian » Recent et Ra Recent * Fic. 24. SEA-CUCUMBERS OF CAMBRIAN AND RECENT SEAS. Eldonia ludwigi of the mid-Cambrian (after Walcott), regarded as pelagic and somewhat resembling a jellyfish, is thought rather to be a form analogous to Pelagothuria nata- irix, a swimming sea-cucumber, although it shows wide differences. The mouth of Pelagothuria is above the swimming umbrella, the posterior part of the body and the anal opening are below: in the fossil Eldonia both mouth and anus hang below. Mackenzia costalis, a mid-Cambrian form (after Walcott), strongly resembling the bur- rowing sea-cucumbers, a recent form of which, Synapta girardit, is shown at the right. Louisella pedunculata, another mid-Cambrian form (after Walcott), and a recent rock-clinging form, Pentacta frondosa. although it also displays wide differences of structure. If Eldonia ludwigi proves to be a holothurian, we witness in mid- 128 THE ORIGIN AND EVOLUTION OF LIFE Cambrian strata members of this order differentiated into at least three widely distinct families. The worms, including swimming and burrowing annulates, are represented in the Bur- ANNULATA gess fauna by a very large number of specimens, com- prising nineteen species, dis- tributed through eleven genera and six families. NVlostwolathesem-atenorrthe order Polycheta, as, for ex- ample, Worthenella cambria, in which the head is armed wei with tentacles, while the segmented body and _ the continuous series of bilobed parapodia are very clear. When compared with such typical living polychetes as Nereis virens and Arabella opalina (Fig. 25), we have clear proof of the modern Recent relationships of these mid- Fic. 25. Worms (ANNULATA) OF THE MIDDLE C et A il CAMBRIAN AND RECENT SEASHORES. aMbTlan Species, aS Well as Canadia spinosa, a mid-Cambrian form (after of Cambrian sea-shore and Walcott) with overlapping groups of scale- : ras like dorsal spines, resembling those of the liv- tidal conditions close ly ing A phroditide, such as Polynoé squamata. similar to those of the pres- W orthenella cambria, a worm of mid-Cambrian ; A rat 2 times (after Walcott), compared with Nereis ent time. specia ization virens and Arabella opalina, recent marine toward the spiny or scaly WOTms. ° ° annulates at this period is emphasized in such forms as Canadia spinosa (Fig. 25), a slowly moving form which shows a development of lateral chet and CAMBRIAN INVERTEBRATES 129 overlapping groups of scale-like dorsal spines comparable only to those of the living Aphroditida. An example of this latter family is Polynoé squamata, furnished with dorsal scales. Still other recent forms, such as Palmyra aurifera Savigny, have groups of spinous scales closely resembling those of Canada. Even the modern freely pro- pelled Chetognatha have their representatives in the mid- Cambrian, for to no other group of invertebrates can Amiskwia sagittiformis Walcott (Fig. 26) be referred, so far as we can judge by its external form. As in the recent Sagitta the body is divided into head, trunk, and a somewhat fish-like tail. Its ' Sagitta Amiskwi single pair of fins of chetognath. iid-Cambrian fl Recent type would perhaps give a Fic. 26. FREELY SWIMMING CHZTOG- : NATHS, CAMBRIAN AND RECENT. clearer affinity to the genus aie ee - ; Amiskwia sagittiformis, a mid-Cambrian Spadella. The conspicuous pair form (after Walcott), has a body di- vided into head, trunk, and tail like the of tentacles which surmounts recent Sagitta, as seen in S. gardinert. the head is absent in modern chetognaths, although some recent species show a pair of sen- sory papilla mounted on a stalk on either side of the head, as in Spadella cephaloptera Bush. The digestive canal and other digestive organs appear through the thin walls of the body. A modern group of jellyfishes, the Scyphomeduse (Fig. 27), is represented by the Middle Cambrian Peytota nathorsti, the elliptical disk of which is seen from below. Although this fossil species is ascribed by Walcott to the group Rhizostome because of a lack of marginal tentacles, the thirty-two radiat- eye: THE ORIGIN AND EVOLUTION OF LIFE ing lobes which are so beautifully preserved in the fossil cor, respond closely with those of the existing genus Dactylometra of the suborder Semostome.. It is possible that the marginal tentacles may have been lost in Peytoza, as so frequently hap- pens in living jellyfishes when in a dying condition. From the Burgess fauna it appears that the pre-Cambrian invertebrates had entered and become completely adapted to all the life zones of the continental and oceanic waters, except possibly the abyssal. All the principal phyla—the segmented Annulata, the jointed Arthropoda (including trilobites, merostomes, crusta- ceans, arachnids, and FIG. 27. JELLYFISH, CAMBRIAN AND RECENT. ; asesee in Peytoia nathorsti, mid-Cambrian (after Walcott), sects) é meduse and and Dactylometra qiuinquecirra, recent. The other ccelenterates 5 thirty-two lobes of the fossil specimen corre- : ‘ spond with the same number often observed in echinoder Ms, brachio- Dactylometra, and the characteristic marginal : moll in - tentacles may have been lost in Peytoia. pods, meets s ( clud ing pelycypods, gastro- pods, ammonites, and other cephalopods), and sponges—were all clearly established in pre-Cambrian times. Which one of these great invertebrate divisions gave rise to the vertebrates remains to be determined by future discovery. At present the Annulata, Arthropoda, and Echinodermata all have their advocates as being theoretically related to the ancestors of the vertebrates. The evolution of each of these invertebrate types follows the laws of adaptive radiation, and in the case of the articulates and molluscs extends into the terrestrial and arboreal habitat zones, while many branches of the articulates enter the aérial zone. EVOLUTION OF DIVERGENT AND ANALOGOUS MODES OF RESPIRATION, MOTION, FEEDING, OFFENSE AND DEFENSE. eae a ae eek ————— fF - a a” = = a = = s = oa = By = ee a a Se gD Rl Oa A ae fl oc a, nl = Ls a Fa oc a = Sa wn = = = 3 pT. Bites th Se pa R oy 2 SS -z Pye ee AS = S Aan N i tu a = be = ‘b — ee eee ee —s ———— ee ee ee a eee SSS — N lu a i ee ee ee » — PELAGIC »» ~~ ABYSSAL LAW OF ADAPTIVE RADIATION Fic. 28. THe TWEbLvE CuHIeFr. HABITAT ZONES OF ANIMAL LIFE. These twelve zones compose the environment, aérial to abyssal, into which the Inver- tebrata and Vertebrata have adaptively radiated in the course of geologic time. The Invertebrates range from the abyssal to the aérial zones. The fishes, ranging only from the terrestrio-aquatic to the abyssal habitat zones, nevertheless evolve body forms and types of locomotion similar to those observed in the Amphibia, which range from the littoral to the arboreal habitat zones. The reptiles, birds, and mammals, ranging from the aérial to the pelagic habitat zones, independently evolve through the law of adaptive radiation many convergent, parallel, or similar types of body form, as well as similar modes of locomotion and of offense and defense. ZONAL DISTRIBUTION OF INVERTEBRATE PHYLATYPICALLY QF MARINE ORIGIN ROY W. MINER, APRIL. 1916 MID-CAMBRIAN RECENT a ARBOREAL ARBOR? TERRE TERRESTRIAL | [| FOSSORIAL & TERR? AQUATIC Z | AQUATIC,FLUVEE t » LITTORAL | | AWOL NV » peLacic | \ J vAk ] i ‘ i a » ABYSSAL i fi 2 AVAL = < . i < F is 5 o 86 ohh ee) cae 3 ae te 7 r > § d= MARINE: PELAGIC, LITTORAL, ABYSSAL. SECONDARILY AQUATIC AND TERRESTRIAL Fic. 29. Lire ZONES OF CAMBRIAN AND RECENT INVERTEBRATES. Chart showing in shaded areas the limited habitat zones—Littoral, Pelagic, Abyssal—of the known Cambrian forms (left) compared with the wide adaptive radiation (Abyssal to Arboreal) of recent forms (right). By Roy W. Miner. 131 132 THE ORIGIN AND EVOLUTION OF LIFE The evolution of the articulates! is believed to be as follows: From a pre-Cambrian annelidan (worm-like) stock arose the trilobites with their chitinous armature and many-jointed bodies. ‘The same stock gave rise also to the chitin-armored Fic. 30. ENVIRONMENT. NorTH AMERICA IN CAMBRIAN TIMES. Theoretic restoration of the North American continent (white), continental seas (gray), and ocean (dark gray) in Upper Cambrian (Lower Saint-Croixian) time, during which there occurred the earliest known great invasion of land by the oceans. This period marks the rise of invertebrate gastropods, limulids, eurypterids, and articulate brach- iopods, and the greatest differentiation of trilobites. The lands were probably all low and the climate warm. Detail from the globe model in the American Museum by Chester A. Reeds and George Robertson, after Schuchert. sea-scorpions, or eurypterids, which attained a great size and dominated the seas of Silurian times (Fig. 31). Another line from the same stock is that of the chitin-armored horseshoe crab (Limulus). Out of the eurypterid stock of Silurian times may have come the terrestrial scorpions, fossils of which are 1 Pirsson, Louis V., and Schuchert, Charles, 1915, p. 608. CAMBRIAN INVERTEBRATES Licks first known in the Silurian, and through it arose the entire group of arachnoid (spider-like) animals, including the existing scorpions, spiders, and mites. It is also possible that the Fic. 31. EURYPTERIDS OR SEA-SCORPIONS OF SILURIAN TIMES. A. Restoration of the giant eurypterid, Stylonurus excelsior, from the Catskill sandstone. Natural length, four feet. B. Restoration of Eusarcus, from the Bertie water-lime. Natural length, three feet. C. Restoration of Eusarcus, age of the Bertie water-lime. (After John M. Clarke.) amphibious, terrestrial, and aérial Insecta were derived from some Silurian or Devonian chitin-armored articulate. The true Crustacea also have probably developed out of the same 124 THE ORIGIN AND EVOLUTION OF LIFE pre-Cambrian stock, giving rise to the phyllopods and other true Crustacea of the Cambrian, and to the cirripedes or bar- nacles of the Ordovician. Fic. 32. Norra AMERICA IN MIDDLE DEVONIAN TIMES. Theoretic restoration of the North American continent (white), continental seas (gray), and ocean (dark gray), in Middle Devonian (Hamilton) time. This period is marked by the last extensive inundation of the Arctic seas, by the rise of the Schick- chockian Mountains and many volcanoes in Acadia, and by the beginning of the great Catskill delta built up by rivers from the rising Acadian region. Marine shark and arthrodires become abundant, the American fauna of the Mississippi Sea shows numerous brachiopods and bivalves, and the first evidence of a land flora with large conifers (Dadoxylon) is found. Detail from a globe model in the American Museum by Chester A. Reeds and George Robertson, after Schuchert. REACTIONS TO CLIMATIC AND OTHER ENVIRONMENTAL CHANGES OF GEOLOGIC TIME Schuchert observes that there is no more significant period in the history of the world than the Devonian! (Fig. 32), for at this time the increasing verdure of the land invited the 1 Pirsson, Louis V., and Schuchert, Charles, 1915, p. 714. *‘JAOPONYIS Joye uojurjunyY wor poyIpoyy “WoOMN[OAsI urejunow jo sporisd puv ‘uorsvaut o1ue900 pur uorIsseidap [e}JUNUT]UOD WNUTxeUr Jo sporiod ‘uorjzeloRIS [eUY ay} SuIpooeid saraydsturay W19YINOs pue WoYy}IOU oY} UI UOT}eeIS Jo sy~poda yenjoe puv IJo100q} IY} OsTe fAyIprumy Jo pue Apple Jo “UOTPLUTIOF 9UOJSIUTT] JO “UOT]LUIOJ [VOD Jo sported uUMUTUIU pu LINWIXvUL oY} SMOYS JIL sIYT, ‘“saseyd of] pue ‘oruvI00 “PeJUIUT}UOD ‘OT}VUMI[D JO WOT}LIIIIOD ITJoIOIT I, ‘SUVA NOITIJ AXOJ XO ALA ISVG AHL ONTANG INANNOAIANY ONIONVHD “ff “OL genie 5 oes NSSDANL| NSSOLLT | UDULLAT ‘fiuogang | “fruogung upwuonagy | uDLingig saddp 4anoT aaddQ L907 i at DIMMU YR4ON fo suornjoaas WY PUP UYU YY, YY unjqunoyy SainjgoLoadua J 12200) ies eens et 7 ie os uoynutof jp00 fo sporlag ps 135 136 THE ORIGIN AND EVOLUTION OF LIFE invasion of life from the waters, the first conquest of the terres- trial environment being attained by the scorpions, shell-fish, worms, and insects. This is an instance of the constant dispersion of animal forms into new environments in search of their food-supply, the chief instinctive cause of all migration. This impulse is con- stantly acting and react- ing throughout geologic time with the migration of the environment, which is graphically pre- sented by Huntington’s chart (Fig. 33), from the researches of Barrell, Schuchert, and others. The periodic readjust- Fic. 34. Fosstt STARFISHES. ment of the earth crust A portion of petrified sea bottom of Devonian age, of North America! is showing fossil starfishes associated with and t, Ca er t devouring bivalves as starfishes attack oyster- witnesse In fourteen beds at the present time. Hamilton group, periods of mountain- Saugerties, N. Y. After John M. Clarke. | making (oblique lines), concluding with the Appalachian Range, the Sierra Nevada (Sierran), the Rocky Mountains (Laramide), and the Pacific Coast Range. Between these relatively short periods of mountain up- heaval came? periods of continental depression and oceanic invasion (horizontal lines) when the continent was more or less flooded by the oceans. ‘There are certainly twelve and probably not less than seventeen periods of continental flood- 1 Pirsson, Louis V., and Schuchert, Charles, 1915, p. 979. 4 Od, cit., p. 982. ENVIRONMENTAL CHANGES 137 ing which vary in extent up to the submergence of 4,000,000 square miles of surface. Each of these changes, which by some geologists are be- lieved to be cyclic, included long epochs especially favorable to certain forms of life, resulting in the majority of cases in high specialization like that of the sea-scorpions (eurypterids) followed by more or less sudden extinction. In the oceans the life most directly influenced was that of the lime-secreting organisms which resulted in maximum and minimum periods of limestone formation (oblique lines) by alge, pelagic fora- minifera, and corals. On land there were two greater (Car- boniferous, Upper Cretaceous) and several lesser periods of coal formation. Changes of environment play so large and conspicuous a part in the selection and elimination of the invertebrates that the assertion is often made that environment is the cause of evolution, a statement only partly consistent with our funda- mental biologic law, which finds that the causes of evolution lie within the four complexes of action, reaction, and inter- action (see p. 21). Perrin Smith, who has made a most exhaustive analysis of the evolution of the cephalopod molluscs and especially of the Triassic ammonites, observes that the evolution of form continues uninterruptedly, even where there is no evidence whatever of environmental change. Conversely, environmen- tal change does not necessarily induce evolution—for exam- ple, during the Age of Mammals, although the mammals de- veloped an infinite variety of widely divergent forms, the rep- tiles (p. 231) show very little change. 138 THE ORIGIN AND EVOLUTION OF LIFE THE MUTATIONS OF WAAGEN d When Darwin published the “Origin of Species,’”’ in 1859, no one had actually observed how one form of animal or plant actually passes into another, whether according to some definite law or principle, or whether fortuitously or by chance. So far as we know, the honor of first observing how new specific forms arise belongs to Wilhelm Heinrich Waagen.! It was among the fossil ammonites of the Jurassic, which are repre- sented by the existing pearly nautilus, that Waagen first ob- served the actual mode of transformation of one animal form into another, as set forth in his classic paper of 1869, “ Die Formenreihe des Ammonites subradiatus.”* The essential fea- ture of the ‘‘mutation of Waagen’’® is that it established the law of minute and inconspicuous changes of form which ac- cumulate so gradually that they are observable only after a considerable passage of time, and which take a definite direc- tion as expressed in the word Mutationsrichtung. We now recognize that they represent a true evolution of the heredity- chromatin. This law of definitely directed evolution is illus- trated in the detailed structure of the type series of ammon- ites (Fig. 35) in which Waagen’s discovery was made. It has proved to be a fundamental law of the evolution of form, for it is observed alike in invertebrates and vertebrates wherever a closely successive series can be obtained. Among the fossil invertebrates a mutation series of the brachiopod, S‘pirifer mucronatus of the Middle Devonian or Hamilton time, is one of the most typical (Fig. 36). The essential law discovered by Waagen is one of the most 1 Born in 1841, died in 1900. An Austrian paleontologist and stratigraphic geologist. * Waagen, Wilhelm, 1869. 3 The term “‘mutation”’ used in this sense was introduced by Waagen in 1869. Twenty years later the great Austrian paleontologist Neumayr defined the “ Mutationsrichtung” as the tendency of form to evolve in certain definite directions. See Neumayr, M., 1880, pp. 60, 61. MUTATIONS OF WAAGEN 139 important in the whole history of biology. It is that certain new characters arise definitely and continuously, and, as Osborn has subsequently shown,! adaptively. This law of the Zone des A, MACROCEPHALUS Zone des A. ASPIDOIDES Zone der TERDIGONA A. LATILOBATUS A. ASPIDOIDES en A, ~~“ SUBRADIATUS Zone des A, FERRUGINEUS Zone des A, PARKINSONI Zone des A. HUMPHRIESIANUS A. SUBRADIATUS es ee ee ee ee See ee 4 senator Gui COLLECTIVART— A. SUBRADIATUS Fic. 35. CONTINUOUS CHARACTER CHANGES KNOWN AS THE MUTATIONS OF WAAGEN. Successive geologic mutations of Ammonites subradiatus, drawn and rearranged from the original plates published by Waagen in 1869, showing his type series of the contin- uous character changes known as the Mutations of Waagen. 1Qsborn, Henry Fairfield, 1912.1. 140 THE ORIGIN AND EVOLUTION OF LIFE gradual evolution of adaptive form is directly contrary to Darwin’s theoretic principle of the selection of chance varia- tions. It is unfortunate that the same term, mutation, was chosen by the botanist, Hugo de Vries, in 1901, to express his observation that certain characters in plants arise by sudden THEDFORDENSE = ANTRIM BLACK SHALE 1s b @| pantioce PT. BEDS ‘~-— -——S| POTTER FARM BEDS ATEENUATUS Ssoe > Foe eS 2 ae TROWBRIDGE MILLS ALPENA LIMESTONE MULTIPLICATUS >> | SOMMERVILLE LIMESTON! ELCAJON CLAY SUNNYSIDE LIMESTONE ALPENENSE > MIDOLE LAKE SHALE (1.77) COLLECTIVART-—SPIRIFER MUCRONATUS Fic. 36.. SuccEssIvE Mutations oF Spirifer mucronatus. Specimens from the geologic section at Alpena, Mich., on the shore of Lake Huron, and from the corresponding section at Thedford across the lake on the Canadian shore, arranged by A. Grabau to show the relationships of the various mutations. In the scale of strata at the right 814 mm. equals too feet depth. changes (saltations) or discontinuously, and without any defi- nite direction or adaptive trend (Mutationsrichtung). The essential feature of de Vries’s observations, in contrast to Waagen’s, is that of discontinuous saltations in directions that are entirely fortuitous—that is, either in an adaptive or in- adaptive direction, the direction to be subsequently deter- mined by selection—a theoretic principle agreeing closely with that of Darwin. CHAP TE RIV VISIBLE AND INVISIBLE EVOLUTION OF THE VERTEBRATES Chromatin evolution. Errors and truths in the Lamarckian and Darwinian explanations of the processes of evolution. Character evolution more important than species evolution. Individuality in character origin, velocity, and cooperation. Origin of the vertebrate type. The laws of convergence, divergence, and adaptive radiation of form. SIMON NeEwcoms! considered the concept of the rapid movement of the solar system toward Lyra as the greatest which has ever entered the human mind. He remarks: “If I were asked what is the greatest fact that the intellect of man has ever brought to light, I should say it was this: Through all human history, nay, so far as we can discover, from the infancy of time, our solar system—sun, planets, and moons—has been flying through space toward the constellation Lyra with a speed of which we have no example on earth. ‘To form a con- ception of this fact the reader has only to look at the beauti- ful Lyra and reflect that for every second that the clock tells off we are ten miles nearer to that constellation.” The history of the back-boned animals (Vertebrata) as the visible expression of the invisible evolution of the microscopic chromatin presents an equally great concept of the potential- ities of matter in the infinitely minute state. According to this concept our study of the evolution of the back-boned animals at once resolves itself into two parallel lines of inquiry and speculation, which can never be divorced and are always to be followed in observation and inference: 1 Newcomb, Simon, 1902 (ed. of 1904, p. 325). I41 142 THE ORIGIN AND EVOLUTION OF LIFE The Visible Body The Invisible Germ The evolution of somatic (7. e., The evolution of HEREDITY- BODILY) FORM and FUNCTION as 0)- CHROMATIN as inferred from the in- served in anatomy, embryology, pa- cessant visible evolution of Form leontology, and physiology. The andFunction. ‘The rise and decline rise, differentiation, and change of _ of potentialities, predispositions, and function in bodily characters. other germinal characters. A clear distinction exists between the slow, stable heredity- chromatin, or germ evolution, and the unstable body cell evolu- tion as viewed by the experimental zoologist. The body is un- stable because it is immediately sensitive to all variations of environment, growth, and habit, while the chromatin alters very slowly. The peculiar significance of heredity-chromatin, when viewed in the long perspective of geologic time, is its stability in combination with incessant plasticity and adaptability to varying environmental conditions and new forms of bodily action. Chromatin is far more stable than the surface of the earth. ‘Throughout, the potentiality of constant changes of proportion, gain and loss of characters, genesis of new charac- ters, there is always preserved a large part of the history of antecedent form and function. In the vertebrates chromatin evolution is mirrored in the many continuous series of forms which have been discovered, also in the perfection of mechani- cal detail in organisms of titanic size and inconceivable com- plexity, like the dinosaurs among reptiles and the whales among mammals, which rank with the Sequoza among plants. ADAPTIVE CHARACTERS OF INTERNAL-EXTERNAL ACTION, REACTION, INTERACTION Of the causes! of this slow but wonderful process of chroma- tin evolution there are two historic explanations, each adum- brated in the Greek period of inquiry. hoee Pretace, Driix, EVOLUTION OF THE GERM 143 The older, known as the Lamarckian,! expressed in modern terms, is that the causes of the genesis of new form and new func- tion are to be sought in the body cells (soma), on the hypothesis that cellular actions, reactions, and interactions with each other and with the environment are in some way impressed physico- chemically upon and are heri- This idea was originally suggested table by the chromatin. by the accurate observation of early naturalists and anatomists that bodily function not only controls and perfects form but is generally adaptive or pur- posive in its effects upon form. According to this Lamarck- Spencer-Cope explanation a change of environment, of habit, and of function should al- ways be antecedent to changes of form in succeeding genera- tions; moreover, if this explana- tion were the true one, succes- sive changes in evolutionary series would be like growth, they would be observed to fol- low the direct lines of individ- ual action, reaction, and inter- action, and the young would ADAPTATIONS OF ENVIRONMENTAL Cor- RELATION: RESPIRATORY, OLFACTORY, VISUAL, AUDITORY, THERMAL, GRAVITY FUNCTIONS AND ORGANS COORDINATIVE AND CORRELATIVE TO VARIATIONS OF LIGHT, HEAT, HU- MIDITY, ARIDITY, CAUSED BY MI- GRATIONS OF THE INDIVIDUAL OR OF THE ENVIRONMENT. ADAPTATIONS OF INTERNAL CORRELATION: CORRELATION AND COORDINATION OF THE INTERNAL GROWTH AND FUNC- TIONS THROUGH INTERNAL SECRE- TIONS, ENZYMES, AND THE NER- VOUS SYSTEM. ADAPTATIONS OF NUTRITION (1) ON INORGANIC COMPOUNDS. (2) ON BACTERIA. (3) ON PROTOPHYTA, ALG, ETC. (4) ON PROTOZOA. (5) ON HIGHER PLANTS, HERBIVO- ROUS DIET. (6) ON HIGHER ANIMALS, CARNIVO- ROUS DIET. (7) PARASITIC, WITHOUT OR WITHIN PLANTS AND ANIMALS. ADAPTATIONS OF INDIVIDUAL COMPETI- TION AND SELECTION: (A) SELECTION, AFFECTING VARIA- TION, RECTIGRADATION, MUTA- TION, ORIGIN, AND DEVELOP- MENT OF SINGLE CHARACTERS, PROPORTIONS, ETC. (B) AFFECTING ALL REPRODUCTIVE ORGANS, PRIMARY AND SEC- ONDARY. ADAPTATIONS OF RACIAL COMPETITION AND. SELECTION, AFFECTING CHIEFLY ALL MOTOR, PRO- TECTIVE, OFFENSIVE, AND DEFEN- SIVE STRUCTURES OF THE ENDO- AND EXOSKELETON; ALSO REPRO- DUCTION RATE. THE PECULIAR SIGNIFICANCE OF THE HEREDITY-CHROMATIN is its sta- bility in combination with incessant plasticity and adaptability to vary- ing environmental conditions and new forms of bodily action. 1 Cf. Preface, pp, xiii) xiv. 144 THE ORIGIN AND EVOLUTION OF LIFE be increasingly similar to the adults of antecedent genera- tions, which is frequently the case but unfortunately for the Lamarckian explanation is not zmvariably the case. In many parts of the skeleton chromatin development and degeneration so obviously follow bodily use and disuse that Cope was led to propose a law which he termed bathmism (growth force) and to explain the energy phenomena of use and disuse in the body tissues as the cause of the appearance of corresponding energy potentialities in the chromatin. In other words, he believed that the energy of development or of degeneration in the bodily parts of the individual is inherited by corresponding parts in the germ. Similar opinions prevail among most anatomists (e. g., Cunningham) and among many paleontologists and zo- ologists (e. g., Semon). The opposed explanation, the pure Darwinian,! as restated by Weismann and de Vries, is that the genesis of new form and function is to be sought in the germ cells or chromatin. ‘This is based upon an hypothesis which is directly anti-Lamarckian, that the actions, reactions, and interactions which cause cer- tain bodily organs to originate, to develop, or to degenerate, to exhibit momentum or inertia in development, do not give rise to corresponding sets of predispositions in the chromatin, and are thus not heritable. According to this explanation, body cell changes do not exert any corresponding specific in- fluence on the germ cells. All predispositions to new form and function not only begin in the germ cells but are more or less lawless or experimental; they are constantly being tested or tried out by bodily experience, habits, and functions. Techni- cally stated, they are “fortuitous”? or chance variations, fol- lowed by selection of the fittest variations, and thus giving rise to adaptations. Thus Darwin’s disciple, Poulton, also de L. Cf. Pretace spi alve EVOLUTION OF THE GERM 145 Vries, who has merely restated in his law of ‘mutation’? Dar- win’s original principle of 1859, and Bateson, the most radical thinker of the three, hold the opinion that there is no adaptive law observed in germ variation, but that the chromatin is con- tinuously experimenting, and that from these experiments se- lection guides the organism into adaptive and purposive lines. This is the prevailing opinion among most modern experimental zoologists and many other biologists. Neither the Lamarckian nor the Darwinian explanation accords with all that we are learning through paleontology and experimental zoology of the actual modes of the origin and development of adaptive characters. That there may be ele- ments of truth in each explanation is evident from the follow- ing consideration of our fundamental biologic law. Adaptive characters present three phases: first, the origin of character form and character function; second, the more or less rapid acceleration or retardation of character form and function; third, the coordination and cooperation of character form and func- tion. If we adopt the physicochemical theory of the origin and development of life it follows that the causes of such origin, velocity (acceleration or retardation) and cooperation must lie somewhere within the actions, reactions, and interac- tions of the four physicochemical complexes, namely, the physical environment, the developing organism, the heredity- chromatin, the living environment, because these are the only reservoirs of matter and energy we know of in life history. While it is possible that the relations of these four energy complexes will never be fathomed, it is certain that our search for causes must proceed along the line of determining which actions, reactions, and interactions invariably precede and which invariably follow those of the body cells (Lamarckian view) or those of the chromatin (Darwin-Weismann view). 140 THE ORIGIN AND EVOLUTION OF LIFE The Lamarckian view that adaptation in the body cells znvart- ably precedes similar adaptive reaction in the chromatin is not supported either by experiment or by observation; such pre- cedence, while occasional and even frequent, is by no means invariable. The Darwinian view, namely, that chromatin evolution is a matter of chance and displays itself in a variety of directions, is contradicted by paleontological evidence both in the Invertebrata and Vertebrata, among which we observe that continuity and law in chromatin evolution prevails over the evidence either of fortuity or of sudden leaps or mutations, that in the genesis of many characters there 1s a slow and prolonged rectigradation or direct evolution of the chromatin toward adaptive ends. This is what is meant in our introduction (p. 9) by the statement that in evolution law prevails over chance. VISIBLE CHARACTERS, INVISIBLE CHROMATIN DETERMINERS The chief quest of evolutionists to-day in every field of observation is the mode and cause of the origin and subsequent history of single characters. The quest of Darwin for the causes of the origin of species has now become an incidental or side issue, since, given a number of new or modified heredity char- acters,’ presto, we have a new species. In this present aspect of research the discoveries of modern paleontology are in accord with many of the recently discovered laws of heredity. The paleontologist supports the observer of heredity in dem- onstrating that every vertebrate organism is a mosaic of an ' Character (Greek, yxoaxche, metaph., a distinctive mark, characteristic, character) is the most elastic term in modern biology; we may apply it to every part and function of the organism, large or small, which may evolve separately and be inherited separately. Mendel has shown that “‘characters’’ are far more minutely separable in the invisible chromatin than they are in the visible organism; also that every bodily ‘‘character”’ is a complex of numerous germ ‘‘characters,”’ which are technically known as determiners or factors. For example, such a simple visible character as eye color in the fruit-fly is known to have determiners in the chromatin. Morgan, Thomas Hunt, 1916, pp. 118-124. CHARACTER EVOLUTION 147 inconceivably large number of ‘‘characters”’ or ‘‘character complexes,” structural and functional, some indissolubly and invariably grouped and cooperating, others singularly inde- pendent. For example, the zoologist infers that every one of the most minute scales of a reptile or hairs of a mammal is a “character complex” having its particular chemical formule and chemical energies which condition the shape, the color, the function, and all other features of the complex. Through researches on heredity each of these characters and character complexes is now believed to have a corresponding physico- chemical determiner or group of determiners in the germ- chromatin, the chromatin existing not as a miniature, but as an individual potential and causal. In the course of normal physicochemical environment, of normal life environment, of normal individual development, and of normal selection and competition, an organism will tend to more or less closely reproduce its normal ancestral charac- ters. But a new or abnormal physicochemical intruder either into the environment, the developing individual, the heredity- chromatin or the life environment may produce a new or abnor- mal visible character type. This quadruple nature of the physicochemical energies directed upon each and every char- acter is fetrakinetic in the sense that it represents four complexes of energy; it is /etraplastic in the sense that it moulds bodily development from four different complexes of causes. This law largely underlies what we call variation of type. In other words, the normal actions, reactions, and inter- actions must prevail throughout the whole course of growth from the germ to the adult; otherwise the visible body (pheno- type, Johannsen) may not correspond with the normal expres- sion of the potentialities of the invisible germ (genotype, Jo- hannsen). 148 THE ORIGIN AND EVOLUTION OF LIFE The principle of individuality, namely, of separate develop- ment and existence, which we have seen to be the prime char- acteristic of the first chemical assemblage into an organism (p. 68), also governs each of the character complexes, as ob- served by the paleontologist. In some vertebrates we observe an infinity of similar character com- plexes, evolving in an exactly similar manner, as in the beautiful mark- ings of the shell and the exquisite B Fic. 37. SIMILARLY FORMED CHARACTERS IN THE GLYPTODON. Shell pattern and tooth pattern of the Glyptodon, a heavily armored fossil armadillo found in North and South America. The entire shell is covered with rosettes, composed of small plates nearly uniform in design, similar to those in the very small section repre- sented (A). The entire series of upper and lower teeth bear within a uniform “‘glyptic” pattern, like that of the tooth shown here (B), to which the name Glyptodon refers. enamel pattern of the teeth of the heavily armored. armadillo known as the glyptodon (Fig. 37), in which respectively every portion of the shell evolves similarly and every one of the teeth evolves similarly, from which we might conclude that there is an absence of separability or individuality in form characters and that some homomorphic (similarly formative) impulse is present in all characters of similar chromatin origin. But such a rash conclusion is offset by the existence of other CHARACTER EVOLUTION 149 character complexes of similar ancestry in which each char- acter evolves differently and is in a high degree heteromorphic (diversely formative), as, for example, in the grinding teeth of mammals (Fig. 38). This individuality and separability inherent in character form is equally observed in character velocity and is the basis of the shifting of characters from adult to youthful stages, or vice versa, as well as of all the pro- portionate and quantitative changes which make up four-fifths of verte- brate evolution. Increasing character velocity is a process of acceleration; decreasing character velocity is a proc- Fre. 38. DrssimriaRLy FORMED CHARACTERS’ OF ess of retardation. Sree Oe Teme For example, in Surface of the upper grinding teeth of two ancient Eocene mammals. Type B is known to be related to the evolution of any group of ani- mals, as in plants (p. 108), two char- aclemmiormsomside by side, like the fingers of the hand or toes of the foot, may evolve with equal velocity and maintain a perfect symmetry, or type A. In Euxprotogonia (A) all the cusps are of a somewhat similar rounded form. In Meniscotherium (B) each cusp has its own : peculiar form. one may be accelerated into a very rapid momentum! while another may be held in a state of absolute inertia or equilibrium, and a third may be retarded. These are the extremes of character velocity which result in the anatomical or visible conditions respectively known as de- velopment, balance, and degeneration. 1In physics momentum equals mass X velocity. In biology momentum and inertia refer to the relative rate of character change, both in individual development (ontogeny) and in evolution (phylogeny). Character parallax would express the differing velocities of two characters. Thus the character parallax of the right and left horns in the Bron- totheriine (titanotheres) is very small, 7. e., they evolve at nearly or quite the same rate; on the other hand, the character parallax between the first and second premolar teeth in these animals is very great. The character-parallax idea has innumerable ap- plications and can be expressed quantitatively. W.K. Gregory. 150 THE ORIGIN AND EVOLUTION OF LIFE The ever changing velocity and changing bodily form and function in character complexes are to be regarded as expressions of physicochemical energy resulting from the actions, reactions, and interactions of different parts of the organism. As we have repeatedly stated, these changes proceed according to some unknown laws. The only vista which we enjoy at pres- sent of a possible fu- ture explanation of the CAUSES. Obechatacter origin, character veloc- ity, and character co- operation is through chemical catalysis, namely, through the hypothesis that all ac- PROPORTIONAL ADAPTATION IN THE FINGERS OF A LEMUR. FIG. 30. This peculiar hand of the Aye-Aye (Cheiromys) of Madagascar affords an excellent example of un- equal velocity in the development of adjacent characters. In this hand each finger has its own proportionate rate of evolution. The thumb (upper) is extremely short; the index finger is normal; the middle finger is excessively slender, tions and reactions of form and of motion liberate specific cata- lytic messengers, such in adaptation to a very special purpose, namely, for insertion into small spaces and crevices in search of larve; the fourth and fifth fingers (two lower) are normal. as ferments, enzymes, hormones, chalones, and other as yet un- discovered chemical messengers, which produce specific and cooperating imteractions in every character complex of the organ- ism and corresponding predispositions in the physicochemical energies of the germ; in other words, that the chemical accelera- tors, balancers, and retarders of body cell development also affect the germ. In our survey of the marvellous visible evolution of the vertebrates we may constantly keep in our imagination this conception of the invisible actions, reactions, and interactions of the hard parts of the structural tissues, which are preserved CHARACTER EVOLUTION I51 in visible form in fossils. In this field of observation the nature of the chemical. and physiological influences of the body can only be inferred, while the relations of these physicochemical influences to those of the chromatin are absolutely unknown. Such a form of explanation would, however, only apply to a pert of the characters of adaptation (table, page 143). The visible and invisible evolution of the hard parts in adaptation resolves itself into six chief and concurrent processes, namely: Ever changing character form and character function, Ever changing character velocity, acceleration, balance, re- tardation, in individual development and in the chromatin, Ever changing character cooperation, coordination and corre- lation, Characters Incessant character origin in the heredity-chromatin, some- and times following, sometimes antecedent to similar charac- | Character ter origin in the developing individual, Complexes Relatively rapid disappearance of character form and charac- ter function in the developing individual, Relatively slow disappearance of the determiners and predis- positions of character form and character function in the heredity-chromatin. | Changes in the visible bodily hard parts invariably mirror the invisible evolution of the chromatin; in fact, this invisible evolution is nowhere revealed in a more extraordinary manner than in the incessantly changing characters in such structures as the labyrinthine foldings of the deep layers of enamel in the grinding teeth of the horse. The chromatin as the potential energy of form and func- tion is at once the most conservative and the most progressive centre of physicochemical evolution; it records the body form of past adaptations, it meets the emergencies of the present through the adaptability to new conditions which it imparts to the organism in its distribution throughout every living cell; it is continuously giving rise to new characters and functions. 152 THE ORIGIN AND EVOLUTION OF LIFE Taking the whole history of vertebrate life from the beginning, we observe that every prolonged, old adaptive phase in a sim- ilar habitat becomes impressed in the hereditary characters of the chromatin. Throughout the development of new adaptive phases the chromatin always retains more or less potentiality of repeating the embryonic, immature, and more rarely some of the mature structures of older adaptive phases in the older environments. This is the basis of the /aw of ancestral re peti- tion, formulated by Louis Agassiz and developed by Haeckel and Hyatt, which dominated biological thought during thirty years of the nineteenth century (1865-1895). It yielded with more or less success a highly speculative solution of the ances- tral form history of the vertebrates, through the study of em- bryonic development and comparative anatomy, long before the actual lines of evolutionary descent were determined through paleontology. LAws OF ForRM EVOLUTION IN ADAPTATION TO THE MECHANTI- CAL AND PHYSICOCHEMICAL ACTIONS, REACTIONS, AND INTERACTIONS OF LOCOMOTION, OFFENSE AND DEFENSE, AND REPRODUCTION The form evolution of the back-boned animals, beginning with the pro-fishes of Cambrian and pre-Cambrian time, ex- tends over a period estimated at not less than 30,000,000 years. The supremely adaptable vertebrate body type be- gins to dominate the living world, overcoming one mechan- ical difficulty after another as it passes through the habitat zones of water, land, and air. Adaptations in the motions necessary for the capture, storage, and release of plant and animal energy continue to control the form of the body and of its appendages, but simultaneously the organism through me- chanical and chemical means protects itself either offensively THE LAWS OF ADAPTATION 153 or defensively and also adapts itself to reproduce and protect its kind, according to Darwin’s original conception of the strug- gle for existence as involving both the hfe of the individual and the life of its progeny. Among all defenseless forms either speed or chemical or elec- trical protection is a prime necessity, while all heavily ar- mored forms gradually aban- don mobility. As among the Invertebrata, calcium carbon- ate and phosphate and various compounds of keratin and chi- tin are the chief chemical ma- terials of defensive armature. Locomotion, as distinguished from that in all invertebrates, is in an elongate body stiffened by a central axis, hence the name chordate or Chordata for the vertebrate division. The evolution of the cartilaginous skeletal supports (endoskeleton) and of the limbs is generally from the centre of the body toward the periphery, the evolu- tion of the epidermal defensive armature (exoskeleton) is from the periphery toward the centre. AGE OF MAN QUATERNARY 2 AGE g OF S TERTIARY ~ MAMMALS | 3] UPPER CRETACEOUS LOWER CRETACEOUS (COMANCHEAN) TRIASSIC PERMIAN PENNSYLVANIAN (UPPER CARBONIFEROUS) MISSISSIPPIAN (us R CARBONIFEROUS) MILLIONS OF YEARS | 3,000,000 |__ YEARS AGE F REPTILES MESOZOIC RATIO 6, 9,000,000 YEARS AGE OF AMPHIBIANS LATE PALAEOZOIC IGNEOUS SECONDARY. ENTOMBED FOSSILS DIRECT EVIDENCE OF FORMER LIFE DEVONIAN AGE OF FISHES MID-PALAEOZOIC SILURIAN PALAEOZOIC ORDOVICIAN ROCKS CHIEFLY UNMETAMORPHOSED: SEDIMENTARY PREDOMINANT; RATIO 12, 18,000,000 YEARS AGE OF INVERTEBRATES EARLY PALAEOZOIC CAMBRIAN 30 MILLIONS KEWEENAWAN F YEARS (ALGONKIAN) ANIMIKIAN LATE PROTEROZOIC 35 EVOLUTION HURONIAN INVERTEBRATES ALGOMIAN PROTEROZOIC 40 : | | EARLY PROTEROZOIC SUDBURIAN | LAURENTIAN a fe} eb ae (Sw oa b a eens ROCKS GENERALLY METAMORPHOSED: heats PREDOMINANT; EVOLUTION UNICELLULAR “PRECAMBRIAN,” RATIO 20, 30,000,000 YEARS SEDIMENTARY SECONDARY. LIMESTONE, IRON ORE, AND GRAPHITE INDIRECT EVIDENCE OF FORMER LIFE. FOSSILS SCARCE. a ARCHAEOZOIC (ARCHEAN) GRENVILLE (KEEWATIN) (COUTCHICHING) Fic. 40. ToTAL GEOLOGIC TIME SCALE, ESTIMATED AT SIXTY MILLION YEARS. These estimates are based upon the relative thickness of the pre-Cambrian and post-Cambrian rocks. Prepared by the author and C. A. Reeds after the time estimates of Walcott and Schuchert. 154 THE ORIGIN AND EVOLUTION OF LIFE The defensive armature finally through change of function makes important contributions to the inner skeleton. The chief advance which has been made in the last fifty years is our abundant knowledge of the modes of adaptation as contrasted with the very limited knowledge yet attained as to the causes of adaptation. The theoretic application of the fundamental law of action, reaction, and interaction becomes increasingly difficult and almost inconceivable as adaptations multiply and are super- posed upon each other with the evolution of the four physico- chemical relations, as follows: Physical environment: succession, reversal, and alternation of habitat zones, Individual development: succession, reversal, and alterna- tion of adaptive habitat phases, a te Chromatin evolution: addition of the determiners of new ea habitat adaptations while preserving the determiners of old habitat adaptations, lepomae au Succession of life environments: caused by the migrations of the individual and of the life environment itself. THE LAW OF CONVERGENCE OR PARALLELISM OF FORM IN LOCOMOTOR, OFFENSIVE, AND DEFENSIVE ADAPTATIONS There arise hundreds of adaptive parallels between the evolution of the Vertebrata and the antecedent evolution of the Invertebrata. Although the structural body type and mechanism of locomotion is profoundly diverse, the combined necessity for protection and locomotion brings about close parallels in body form between such primitive Silurian euryp- terids as Bunodes and the vertebrate armored fishes known as ostracoderms, a superficial resemblance which has led Patten’ to defend the view that the two groups are genetically related. 1 Patten, Wm., 1912. THE LAWS OF ADAPTATION 155 It must be the similarity of the internal physicochemical energies of protoplasm, the similarity in the mechanics of motion, of offense and defense, together with the constant simi- larity of selection, which under- lies the law of convergence or parallelism in adaptation, name- ly, the production of externally similar forms in adaptation to similar external natural forces, a law which escaped the keen ob- servation of Huxley! in his re- markable analysis of the modes of vertebrate evolution pub- lished in 1880. The whole process of motor adaptation in the vertebrates, whether among fishes, amphib- lans, reptiles, birds, or mam- mals, is the solution of a series of mechanical problems, namely, of adjustment to gravity, of overcoming the resistance of water or air in the develop- ment of speed, of the evolution of the limbs in creating levers, fulcra (joints), and pulleys. The fore and hind fins of fishes Sorpotoc -a modern bammal Fic. 41. CONVERGENT ADAPTATION OF ForM IN THREE WHOLLY UNRELATED MARINE VERTEBRATES. Analogous evolution of the swift-swim- ming, fusiform body type (upper) in the shark, a fish; (middle) in the ichthyosaur, a reptile; and (lower) in the dolphin, a mammal—three wholly unrelated animals in which the in- ternal skeletal structure is radically different. After Osborn and Knight. and the fore and hind limbs of mammals evolve uniformly where they are homodynamic and divergently where they are heterodynamic. ‘This principle of homodynamy and _hetero- dynamy applies to the body as a whole and to every one of its PHuxleyeel weet o50. 156 parts, according to two laws: THE ORIGIN AND EVOLUTION OF LIFE first, that each individual part has its own mechanical evolution, and, second, that the same mechanical problem is generally solved on the same principle. HABITAT ADAPTATIONS OF THE VER- TEBRATES TO THE CHANGES OF ENVIRONMENT AERIAL (FLYING, VOLANT TYPES) AERO-ARBOREAL (PARACHUTE, VOLPLANING TYPES) ARBOREAL (CLIMBING, LEAPING,AND BRACHIATING TYPES) ARBOREO-TERRESTRIAL (WALKING AND CLIMBING, SCANSORIAL TYPES) TERRESTRIAL (AMBULATORY, SLOW; SALTATORY, LEAPING; CUMBROUS) CURSORIAL, RAPID; GRAVIPORTAL, SLOW, TERRESTRIO-FOSSORIAL (WALKING AND BURROWING TYPES) FOSSORIAL (BURROWING TYPES) TERRESTRIO-AQUATIC (aMPHIBIOUS TYPES) AQUATIC PALUSTRAL, LACUSTRINE (SURFACE-LIVING, BOTTOM-LIVING) FLUVIATILE FRESH-WATER, SWIFT CURRENT, SLOW- CURRENT; FLUVIO-MARINE TYPES) MARINE LITTORAL SURFACE-LIVING AND BURROWING TYPES) MARINE PELAGIC (FREE SURFACE-LIVING, DRIFTING, FLOAT- ING, SELF-PROPELLING TYPES) MARINE ABYSSAL (DEEP BOTTOM-LIVING TYPES, SLOW- AND SWIFT-MOVING) Each of the chief habitat zones may be divided into many subzones. The vertebrates may mi- grate from one to another of these habitats, or through geophysical changes the environments themselves may migrate. Conditions of locomo- tion result in forms that are quadrupedal, bipedal, pinnipedal, apodal, etc. This, we observe, is invariably the ideal principle, for, unlike man, nature wastes little time on inferior inventions but imme- diately proceeds to superior in- ventions. The three mechanical prob- lems of existence in the water habitat are: the buoyancy of water either by First, overcoming weighting down and increasing the gravity of the body or by the development of special grav- itating organs, which enable animals to rise and descend in this medium; second, the me- chanical problem of overcom- ing the resistance of water in rapid motion, which is accom- plished by means of warped sur- faces and well-designed entrant and re-entrant angles of the body similar to the lines’’ ““stream- of the fastest modern third, the problem of propulsion of the body, which is yachts; accomplished, first, by simuous motion of the entire body, ter- minating in powerful propulsion by the tail fin; supplementary action of the four lateral fins; secondly, by third, by the THE LAWS OF ADAPTATION 157 horizontal steering of the body by means of the median sys- tem of fins. The terrestrial and aérial evolution of the four-limbed types (Tetrapoda) is designed chiefly to overcome the resis- tance of gravity and in a less degree the resistance of the atmos- phere through which the body moves. When the aérial stage evolves, with increasing speed the resistance of the air becomes only slightly less than that of the water in the fish stage, and the warped surfaces, the entrant and re-entrant angles evolved by the flying body are similar to those previously evolved in the rapidly moving fishes. In contrast with this convergence brought about by the sim- ilarity above described of the physicochemical laws of action, reaction, and interaction, and the similarity of the mechanical obstacles encountered by the different races of animals in similar habitats and environmental media, is the law of diver- gence. . BRANCHING OR DIVERGENCE OF FORM, THE LAW OF ADAPTIVE RADIATION In general the /aw of divergence of form, perceived by La- marck and rediscovered by Darwin, has been expanded by Osborn into the modern Jaw of adaptive radiation, which ex- presses the differentiation of animal form radiating in every direction in response to the necessities of the quest for nour- ishment and the development of new forms of motion in the different habitat zones. The psychic rudiments of this ten- dency to divergence are observed among the single-celled Pro- tozoa (p. 114). Divergence is constantly giving rise to differ- ences in structure, while convergence is constantly giving rise to resemblances of structure. The law of adaptive radiation is a law expressing the modes 158 THE ORIGIN AND EVOLUTION OF LIFE of adaptation of form, which fall under the following great principles of convergence and divergence: 1. Divergent adaptation, by which the members of a primitive stock tend to develop differences of form while radiating into a number of habitat zones. 2. Convergent adaptation, parallel or homoplastic, whereby an- imals from different habitat zones enter a similar habitat zone and acquire many superficial similarities of form. 3. Direct adaptation, for example, in primary migration through an ascending series of habitat zones, aquatic to terres- ee trial, arboreal, aérial. ’ 4. Reversed adaptation, where secondary migration takes a re- Adaptive verse or descending direction from aérial to arboreal, Radiation from arboreal to terrestrial, from terrestrial to aquatic in the | habitat zones. External | 5- 4/ternate adaptation, where the animal departs from an orig- Body inal habitat and primary phase of adaptation into a sec- ondary phase, and then returns from the secondary phase Form of adaptation into a more or less perfect repetition of the primary phase by returning to the primary habitat zone. 6. Change of adaptation (function), by which an organ serving a certain function in one zone is not lost but takes up an entirely new function in a new zone. 7. Symbiotic adaptation, where vertebrate forms exhibit recip- rocal or interlocking adaptations with the form evolution of other vertebrates or invertebrates. It is very important to keep in mind that the body and limb form developed in each adaptive phase is the starting point of the next succeeding phase. Prolonged residence by an animal type in a single habitat zone results in profound alterations in its chromatin and in consequence the history of past phases is more or less clearly recorded. Among the disadvantages of prolonged existence in one life zone are the following: Through the law of compensation, dis- covered by Geoffroy St. Hilaire early in the last century, every vertebrate, in developing and specializing certain organs sacri- THE LAWS OF ADAPTATION 159 fices others; for example, the lateral digits of the foot of the horse are sacrificed for the evolution of the central digit as the animal evolves from tridactylism to monodactylism. These sacrificed parts are never regained; the horse can never regain the tridactyl condition although it may re-enter a habitat zone in which three digits on each foot would serve the pur- poses of locomotion better than one. In this sense chromatin evolution is irreversible. The extinction of vertebrate races has generally been due to the fact that the various types have sacrificed too many characters in their structural and func- tional reactions to a particular life habitat zone. A finely spe- clalized form representing a perfect mechanism in itself which closely interlocks with its physical and living environment reaches a cul-de-sac of structure from which there is no possible emergence by adaptation to a different physical environment or habitat zone. It is these two principles of too close adjust- ment to a single environment and of the non-revival of char- acters once lost by the chromatin which underly the law that the highly specialized and most perfectly adapted types become extinct, while primitive, conservative, and relatively unspe- cialized types invariably become the centres of new adaptive radiations. CHAR RH Ka EVOLUTION OF BODY FORM IN THE FISHES AND AMPHIBIANS Rapid evolution in a relatively constant environment. Mechanism of motion, of offense, and defense. Early armored fishes. Primordial sharks. Rise of existing groups of fishes. Form evolution of the amphibians. Maxi- mum radiation and extinction. A SIGNIFICANT law of fish evolution is that in a practically unchanging environment, that of salt and fresh water, which is relatively constant both as to temperature and chemical con- stitution as compared with the variations of the terrestrial environment, it is steadily progressive and reaches the great- est extremes of form and of function. This indicates that a changing physicochemical environment, although important, is not an essential cause of the evolution of form. The same law holds true in the case of the marine invertebrates (p. 137), as observed by Perrin Smith. A second principle of signifi- cance is that even the lowliest fishes establish the chief glandu- lar and other organs of action, reaction, and interaction which we observe in the higher types of the vertebrates. Especially the glands of internal secretion (p. 74), the centres of inter- action and coordination, are fully developed. MECHANISM OF MOTION, OF OFFENSE, AND DEFENSE Ordovician time, the early Palzozoic Epoch next above the Cambrian, is the period of the first vertebrates known, namely, the fossil remains of fish dermal defenses found near Canon City, Col., as announced by Walcott in 1891, and subse- quently discovered in the region of the present Bighorn 160 EARLIEST KNOWN FISHES 101 Mountains of Wyoming and the Black Hills of South Dakota. Small spines referred to acanthodian sharks are also abundant in the Ordovician of Cafion City, Col. Since they were slow- moving types protected with the beginnings of a dorsal arma- ture composed of small calcareous tubercles, to which the frermasy | eo eo LOWER AGE CRETACEOUS ({COMANCHEAN) REPTILES JURASSIC PENNSYLVANIAN (UPPER CARBONIFEROUS) il noe apeee dial Lat (LCWER CARBONIFEROUS) AGE OF MAN | QUATERNARY o ee N o csi | | ua | 2 | RATIO 6, 9,000,000 YEARS MESOZOIC AGE LATE PALAEOZOIC OF AMPHIBIANS MID-PALAEOZOIC RATIO 12, 18,000,000 YEARS PALAEOZOIC ORDOVICIAN AGE OF INVERTEBRATES EARLY PALAEOZOIC CAMBRIAN ORDER OF APPEARANCE AND EXPANSION OF THE CLASSES OF VERTEBRATE ANIMALS a, Fic. 42. CHRONOLOGIC CHART OF VERTEBRATE SUCCESSION. Successive geologic appearance and epochs of maximum adaptive radiation (expansion) and diminution (contraction) of the five classes of vertebrates, namely, fishes, amphi- bians, reptiles, birds, and mammals. group name Ostracoderm refers, probably these earliest known pro-fishes were not primitive in external form but followed upon a long antecedent stage of vertebrate evolution. In the form evolution of the vertebrates relatively swift-moving, de- fenseless types are invariably antecedent and ancestral to slow- moving, armored types. Ancestral to these Ordovician chor- dates there doubtless existed free-swimming, quickly darting 162 THE ORIGIN AND EVOLUTION OF LIFE types of unarmored fishes. The double-pointed, fusiform body, in which the segmented propelling muscles are external and a stiffening notochord is central, is the fish prototype, which MYOMERES (Muscle, segments) SPINAL NERVE CORD NOTOCHORD (Provertebral axis) as DIGESTIVE TRACT GILL SLITS more or less clearly Survives in the exist- ing lancelets (Amphi- oxus) and in the lar- val stages of the de- generate ascidians. These animals also furnish numerous Fic. 43. THe Existinc LANcELETS (Amphioxus). embryonic and _lar- Fusiform protochordates living in the littoral zone of val proof efor ces the ocean shores, sole survivors of an extremely ancient stage of chordate (pro-vertebrate) evolution. scent from nobler The body is fusiform or doubly pointed, hence the types name Amphioxus. It is stiffened by the continuous ‘ central axis (chorda, notochord). All the other or- Followin g the gans are more or less sharply segmented. After Willey. pro-fishes of Ordovi- cian time, the great group of true fishes begins its form evolu- tion with (A) active, free-swimming, double-pointed types of fusiform shape, adapted to rapid motion through the water and to predaceous habits in pursuit of swift-moving prey. EARLIEST KNOWN FISHES 163 From this type there radiated many others: (B) the deep, narrow-bodied fishes of relatively slow movements, frequenting the middle depths of the waters; (D) the swift-moving, elongate Se te SIE - thy DEPRESSED (GROVELING) Fic. 44. THe Five Principat Types or Bopy Form In FISHES. These begin with (A) the swift-moving, compressed, fusiform types which pass, on the one hand, into (B) laterally compressed, slow-moving, deep-bodied types, and, on the other, into (C) laterally depressed, round, bottom-dwelling, slow-moving types, also into (D) elongate, swift-moving fusiform types which grade into (£) the eel-like, swift- moving, bottom-living types without lateral fins. These five types of body form in fishes arise independently over and over again in the various groups of this class of vertebrates. Partially convergent forms subsequently appear among amphibians, rep- tiles, and mammals. Prepared for the author by W. K. Gregory and Erwin S. Christman. 164 THE ORIGIN AND EVOLUTION OF LIFE types which increasingly depend upon lateral motions of the body for propulsion and thus tend to lose the lateral fins and PALEOGEOGRAPHY, UPPER SILURIAN (SALINA) TIME _ AFTER SCHUCHERT, APRIL, 1916 MARINE DEPOSITS 4 CONTINENTAL DEPOSITS (7 SALT DEPOSITS xx VOLCANOE Fic. 45. NorTH AMERICA IN UPPER SILURIAN TIME. During this period of depression of the Appala- chian region and elevation of the western half of the North American continent occurred the maximum evolution of the most primitive armored fishes, known as Ostracoderms, which were widely distributed in Europe, America, and the Antarctic. After Schuchert, 1916. finally to assume (£) an elongate, eel shape, en- tirely finless, for pro- gression along the bot- tom; (C) the bottom- living forms, in which the body becomes later- ally broadened, the head very large relatively and covered with protective dermal armature, the movements of the ani- mals becoming slower and slower as the dermal defenses develop. This law applies to all the vertebrates, including man, namely: the de- velopment of armor is pari passu with the loss of speed. Conversely, the gain of speed neces- sitates the loss of ar- mor. Smith Wood- ward! has traced similar radiations of body form in the historic evolution of each of the great groups of fishes. The interest of this fivefold law of body-form radiation is greatly enhanced when we find it repeated successively under 1 Smith Woodward, A., 1915. EARLY ARMORED FISHES 105 the law of convergence among the aquatic amphibia, reptiles, and mammals as one of the invariable effects of the coordina- tion of the mechanism of locomotion with that of offense and defense. In each of these four or five great radiations of body form, from the swift-moving to the bottom- or ground- living, slow, armored types, ~ Fic. 46. THE OstTRACODERM Paleas pis there is usually an increase of OF CLAYPOLE AS RESTORED BY DEAN, bodily size, also an increase of specialization, the maximum in both being reached just before the period of extinction arrives. EARLY ARMORED FISHES The armored Ordovician ostracoderms are very little known. The Upper Silurian ostracoderms enjoyed a wide distribution in Europe and Americar am | Meveeinecluide both the fusiform, free-swim- ming type (Birkenia) and the broadly depressed ray- like types (Lanarkia, etc.). Apparently they had not yet acquired cartilaginous lower jaws and were in a lower stage of evolution than the true fishes. Fic. 47. THE ANTIARCHI. The armature is from Armored, bottom-living Ostracoderm type, Bo- the first arranged in shield thriolepis, from the Upper Devonian of Canada, ; with chitinous armature anda pair of anterior and plate form, as seen 1n appendages analogous to those of the euryp- . terid crustaceans. This cluster of animals was Paleasp Ws; from the Upper undoubtedly buried simultaneously while Sjlurian Salina time of Schu- headed against the current in search of food ‘ or for purposes of respiration. After Patten. chert. In this epoch we 100 THE ORIGIN AND EVOLUTION OF LIFE obtain our first glimpses of North American land life in the presence of the oldest known air-breathing animals, the scorpion Fic. 48. THE ARTHRODIRA. (Above.) Restoration of the gigantic Middle Devonian Arthrodiran (jointed neck) fish Dinichthys intermedius, eight feet in length, of the Cleveland shales (Ohio), showing the bony teeth and bony armature of the head region. (Below.) Lateral view of the same. Model by Dr. Louis Hussakof and Mr. Horter, in the American Museum of Natural History. spiders, also of the first known land plants. There are indica- tions of an arid climate in many parts of the world. In Upper Silurian time the ostracoderms attain the slow, armored, bottom-living stage of evolution, typified in the ptera- spidians and cephalaspidians, which were widely distributed in Europe, in America, and pos- sibly in the Antarctic regions, as indicated by recent explora- tions there. Belonging to an- other and very distinct order, or subclass (Antiarchi), are certain armored Devonian forms (Both- riolepis, Pterichthys, etc.), which possessed a pair of jointed lat- eral appendages. Some of these fishes, which are propelled by a pair of appendages at- tached to the anterior portion of the body, present analogies to the eurypterids (Merostomata, or Arachnida). In the fresh-water deposits of Lower Devonian age have been discovered the ancestors of the heavily armored fishes PRIMORDIAL SHARKS 167 known as the Arthrodira, a group of uncertain relationships. They have many adaptations in common with Bothriolepis, such as the jointed neck, dermal jaws, carapace, plastron, and paired appendages (Acanthaspis). Some authorities regard the Arthrodira as aberrant lung-fishes. others regard the balance of evidence as in favor of relationship with the stem of the Antiarchi (Bothriolepis). In the Middle Devonian (the Cleveland shales of Ohio) they attain the formi- dable size shown in the species Dean, Hussakof, and Dinichthys intermedius (Fig. 48). Like the ostracoderms, these animals are not in the central or main lines of fish evolution but represent collateral lines | yr (. Y Fic. 49. A PRIMITIVE DEVONIAN SHARK. (Above.) Cladoselache, the type of the primitive Devonian shark of Ohio with paired and median lappet fins provided with rod-like cartilaginous supports, from which type by fusion the limbs of which early attained a very high degree of specialization which was followed by extinction. PRIMORDIAL SHARKS, ANCES- TRAL TO HIGHER VER- TEBRATES The central line of fish evolution, destined to give rise all the higher land vertebrates have been derived. Model by Dean, Hussa- kof, and Horter from specimens in the American Museum of Natural History. (Below.) The interior structure of the lappet fins of Cladoselache showing the cartilaginous rays (white) within ; the fin (black). After Dean. to all the higher and modern fish types, is found in the typical cartilaginous skeleton and jaws and four fins of the primordial sharks, the primitive fusiform stage of which appears in the spine-finned type (acanthodian, Diplacanthus, Fig. 51) of Upper Silurian time. The relatively large-headed, bottom-living types of sharks do not appear until the Devonian, during which epoch the early swift-moving, fusiform, predaceous types through a partly reversed adaptation 168 THE ORIGIN AND EVOLUTION OF LIFE branch off into the elongated eel-shaped forms of the Car- boniferous. The prototype of the shark group is the Cladoselache (Fig. 49), a fish famed in the annals of comparative anatomy since it demonstrates that the fins of fishes arise from lateral skin ASCID-AMPHI- €XS Oz SHARKS_ STUR-. _GAR-_. BOWFIN_E: 5 a & RAYS ONS PIKES sabes a os i Qi ; T JURASSIC TRIASSIC PERMIAN PENNSYLVANIAN (UPPER CARBONIFEROUS) MISSISSIPPIAN (LOWER CARBONIFEROUS) Q Re... 3 Dy SS WA \EkZ: & Wee :. 4. a ae Ge 3 7 i z \ \ PRIMITIVE FIRS OBE. FINED IRST LAND- DEVODAN SHARKS L VERTEBRATE Z Al X \ ~~ ~~ ages oe SILURIAN z Y ERMS ORDOVICIAN FISHES WITH GILL-ARCH JAWS. PALAEOZOIC - SHARK SIOCK OSTRACODERMS EARLY PALAEOZOIC "2 SOFT- SKINNED ) CHORDATES CAMBRIAN ORIGIN AND ADAPTIVE RADIATION OF THE FISHES W..K. GREGORY, 1916 Fic. 50. ORIGIN AND ADAPTIVE RADIATION OF THE FISHES. This chart shows the now extinct Siluro-Devonian groups, the Ostracoderms and Arthro- dires, in relation to the surviving lampreys (Cyclostomes); sharks and rays (Elasmo- branchs); sturgeons, garpikes, and bowfins (Ganoids); bony fishes (Teleosts); primi- tive and recent lung-fishes (Dipnoi); and finally the fringe-finned or lobe-finned Ganoids (Crossopterygii) from the cartilaginous fins of which the fore and hind limbs of the first land-living vertebrates (Tetrapoda) were derived. Dotted areas represent groups which still exist. Hatched areas represent extinct groups. Prepared for the author by W. K. Gregory. folds of the body, into which are extended internal stiffening cartilaginous rods (Fig. 49). In course of evolution these rods are concentrated to form the central axis of a freely jointed fin, while in a further step of evolution they transform into the cartilages and bones of the limb girdles and limb segments of the four-footed land vertebrates, the Tetrapoda. The manner of this fin and limb transformation has been one of the greatest problems in the history of the origin of RISE OF MODERN: FISHES 169 animal form since the earliest researches of Carl Gegenbaur, of Heidelberg, who sought to derive the lateral fins from a modification through a profound change of adaptation (func- tion) of the cartilaginous rods which support the respiratory gill arches. While paleontology has disproved Gegenbaur’s hypothesis that the limbs of the higher vertebrates, including those of man, are derived from the cartilaginous gill arches of fishes, it has helped to demonstrate the truth of Reichert’s anatomical hypothesis that the bony chain of the middle ear of man has been derived through change of adaptation from a portion of a modified gill arch, namely, the mandibular carti- lage of the fish. The cycle of shark evolution in course of geologic time embraces a majority of the swift-moving, predaceous types, which radiate into the sinuous, elongate body of the frilled shark (Chlamydoselache) and into forms with broadly depressed bodies, such as the bottom-living skates and rays. Under the law of adaptive radiation the sharks seek every possible habitat zone except the abyssal in the search for food. The nearest approach to the evolution of the eel-shaped type among the sharks are certain forms discovered in Carboniferous time. RISE OF MODERN FISHES By Upper Devonian time the fishes in general had already radiated into all the great existing groups. The primitive armored arthrodires and ostracoderms were nearing extinc- tion. ‘The sharks were still in the early lappet-fin stage of evolution above described, a common characteristic of the members of this entire order being that they never evolved a solid bony armature, finding sufficient protection in the sha- green covering. The scaled armature of the first true ganoid, enamel-cov- 170 THE ORIGIN AND EVOLUTION OF LIFE ered fishes (Osteolepis, Cheirolepis) now makes its first appear- ance. These armored knights of the sea are descended from simpler scaly forms which also gave rise to the rich stock of sturgeons, garpikes, bowfins, and true bony fishes (teleosts) which now dominate all other fish groups both in the fresh Fic. 51. Fish TyPES FROM THE OLD RED SANDSTONE OF SCOTLAND. Upper Devonian time. Primitive ganoids, primitive spine-finned sharks, bottom-living Ostracoderms, partly armored ganoids, and the first lung-fishes. 1. Osteolepis, primitive lobe-finned ganoid. 2. Holoptychius, fringe-finned ganoid. 3, 6. Cheiracanthus, spine- finned shark (Acanthodian). 4. Diplacanthus, spine-finned shark (Acanthodian). 5. Coccosteus, primitive Arthrodiran. 7. Chetrolepis, primitive ganoid. 8,9. Dzpterus, primitive lung-fish. Pterichthys, bottom-living Ostracoderm allied to Bothriolepis. Restorations by Dean, Hussakof, and Horter, partly after Traquair. Models in the American Museum of Natural History. waters and the seas. Remotely allied to this stock are the first air-breathing lung-fishes (Dipnoi), represented by Dipterus ; also the “lobe-finned,”’ or “‘fringe-finned”’ ganoids from which the first land vertebrates were derived. From a single locality, in the Old Red Sandstone of Scotland, Traquair has recovered RISE OF MODERN FISHES I7I a whole fossil series of these archaic fish types as they lived together in the fresh water or the brackish pools of Upper De- vonian time. (Fig. 51). In this period the paleogeographers (Schuchert) obtain their first knowledge of the evolution of the terrestrial environment in the indications of the existence of parallel mountain ranges on the British Isles, of active volcanoes in the Gaspé region of PALEOGEOGRAPHY, EARLY LOWER DEVONIAN (HELDERBERGIAN-GEDINNIAN-HERCYNIAN-KONIEPRUSSIAN) TIME AFTER SCHUCHERT, APRIL, 1916 o wanine DEPOSITS CONTINENTAL DEPOSITS ,x* MOUNTAINS AND VOLCANOES Fic. 52. THEORETIC WORLD ENVIRONMENT IN EARLY LOWER DEVONIAN TIMES. The period of the early appearance of terrestrial invertebrates and vertebrates. This shows the hypothetical South Atlantic continent Gondwana and the Eurasiatic inland sea Tethys, according to the hypotheses of Suess. Modified after Schuchert, 1916. New Brunswick, of the mountain formations of South Africa, and of the depressions of the centre of the Eurasiatic continent into the great central Mediterranean Sea, known as the Jethys of the great Austrian geologist, Suess. In the seas of this time, as compared with Cambrian seas, we observe that the trilo- bites are in a degenerate phase, the brachiopods are relatively less numerous, the echinoderms are represented by the bottom- diigp: THE ORIGIN AND EVOLUTION OF LIFE living starfishes, sharks are abundant, and arthrodiran fishes are still abundant in Germany. It was long believed that the air-and-water-breathing Am- phibia evolved from the Dipnoi, the air-breathing fishes of the inland fresh waters, and this hypothesis was stoutly main- FIN STAGE FOOT STAGE RHIPIDISTIAN FISH AMPHIBIAN ‘ (DEVONIAN) (CARBONIFEROUS) Fic. 53. CHANGE OF ADAPTATION IN THE LIMBS OF. VERTEBRATES. The upper figures represent the theoretic mode of metamorphosis of the fringe-fin of the Crossopterygian fish (left) into the foot of an amphibian (right) through loss of the dermal fringe border and rearrangement of the cartilaginous supports of the lobe. After Klaatsch. The lower figures represent (left) the theoretic mode of direct original evolution of the bones of the fringe-fin (A, B) of a Crossopterygian fish—the Rhipidistia type of Cope— into the bony, five-rayed limb (C) of an amphibian of the Carboniferous Epoch (after Gregory); and (right) the secondary, reversed evolution of the five-rayed limb of a land reptile (A) into the fin or paddle (B, C) of an ichthyosaur (after Osborn). tained by Carl Gegenbaur, who also upheld what he termed the archipterygian theory of the origin of the vertebrate lmb, namely, that the prototype of the modern limbed forms of terrestrial vertebrates is to be found in the fin of the modern Australian lung-fish, Ceratodus. ‘This hypothesis of Gegen- baur, which has been warmly supported by a talented group of his students, is memorable as the last of the great hypotheses regarding vertebrate descent to be founded exclusively upon RISE OF MODERN FISHES 173 Fic. 54. EXTREMES OF ADAPTATION IN LOCOMOTION AND ILLUMINATION. Extremes of adaptation in the existing bony fishes (Teleosts) of the Abyssal Zone of the Oceans. Although many different or- ders of Teleosts are represented, each type has independently acquired phosphores- cent organs, affording a fine example of the law of adaptive convergence. The body form in these fishes is of great diversity. 1. Thread-eel, Nemichthys scolopaceus Richardson. 2. Barathronus diaphanus Brauer. 3. Neoscopelus macrole- pidotus Johnson. 4, 5. Gastrostomus bairdi Gill and Ryder. 6. Gigantactis ranhoeffent Brauer. 7. Sternoptyx diaphana Lowe. 8. Gigantura chuni Brauer. 9. Melanostomias melanops Brauer. 10. Stylophthalmus paradoxus Brauer. 11. Opisthoproctus solcatus Vaillant. After models in the American Museum of Natural History. comparative anatomy and embryology as opposed to the triple evidence afforded by these sciences when reinforced by paleontology. 174 THE ORIGIN AND EVOLUTION OF LIFE It is through the discovery of primitive types of the fringe- finned ganoids, to which Huxley gave the appropriate name Crossopterygia, in reference to the fringe of dermal rays around a central lobe-fin of cartilaginous rods, that the true ancestry of the Amphibia and of the amphibian limb has been traced. This is now regarded as due to a partial change of adaptation, *28 nite SER ih ng Fic. 55. PHOSPHORESCENT ILLUMINATING ORGANS. The abyssal fishes represented in Fig. 54 as they are supposed to appear in the darkness of the ocean depths. After models in the American Museum of Natural History. incident to the passage of the animal from the littoral life zone to the shore zone, whereby the propelling fin was gradually transformed into the propelling limb. This transformation implies a long terrestrio-aquatic phase, in which the fin was partly used for propulsion on muddy surfaces (Fig. 53). In the reversed parallel retrogressive evolution of the lung- fishes (Lepidosiren, Gymnotus), of the fringe-finned fishes (Cala- moichthys) and of the bony fishes (Anguilla), the final eel-shaped, RISE OF MODERN FISHES 175 finless stage is through convergent adaptation either approached or actually passed. The bony fishes (teleosts), which first emerge as a distinct group in Jurassic time, body-form types which had been previously at- tained by the older groups, more or less closely imitating each in turn, so that it is not easy to distinguish su- perficially between the armored catfishes (Lori- caria) of the existing South American waters and their prototypes (Cephalaspis) of the Gat lyemiealeozoic.., ‘The most extreme specializa- tion in the great group of bony fishes is to be found in the radiations of abyssal fishes into slow- and swift-moving forms which inhabit the great depths of the ocean and are adapted to tons of water-pres- sure, to temperatures just above the freezing radiate adaptively into all the great aN Re: aed 70 PALEOGEOGRAPHY, UPPER DEVONIAN (GENESEE-PORTAGE) TIME AFTER SCHUCHERT, APRIL, 1916 PS MARINE DEPOSITS 7S CONTINENTAL DEPOSITS — xxx MOUNTAINS AND VOLCANOES eo DEEP WELLS Fic.56. NortTHAMERICA IN UPPER DEVONIAN TIME. The maximum evolution of the Arthrodiran fishes (Dinichthys, etc.) and of the ganoids of the Upper Devonian of Scotland, the establishment of all the great modern orders of fishes excepting the bony fishes (Teleosts), and the appearance of the first land vertebrates, the amphibians (Thinopus), took place during this period of depression of the western centre of the North American continent. Modified after Schuchert. point, and to total absence of sunlight which is compensated for by the evolution of a great variety of phosphorescent light- 176 THE ORIGIN AND EVOLUTION OF LIFE producing organs in the fishes themselves and in other animals on which they prey. Another extreme of chemical evolution among the fishes is the production of electricity as a protective function, which is Fic. 57. THE EARLIEST Known LIMBED ANIMAL. Footprint of Thinopus anti- guus Marsh, an amphibian from the Upper Devonian of Pennsylvania. Type in the Peabody Museum of Yale University. Photograph of cast presented to the Ameri- can Museum of Natural His- tory by the Peabody Museum. even more effective than bony arma- ture because it does not interfere with rapid locomotion. In only a few of the= fishes# 1s OF {COMANCHEAN) 4 REPTILES a ¢ j sunassic | S 3 TRIASSIC LABYRINTHO- DONTS MESOZOIC LYSO- ROPHUS a —_——— SS ee —__ EMBOLOMERI. RHACHITOMI CRICOTUS YOP: AISTOPODA (SNAKE-LIKE MICROSAURS) PENNSYLVANIAN Pt MICROSAURS BRANCHIOSAURS CARBONIFEROUS) | FIRSTREPTILES AGE OF AMPHIBIANS LATE PALAEOZOIC PRIMITIVE STEGOCEPHS (LOXOM — —— Se essere essere FIRST BATRACHIANS THINOPUS DEVONIAN RHIPIDISTIAN FISHES LUNGFISHES (LOBE-FINNED GANOIDS) SILURIAN Biren 7GANOID STOCK ORDOVICIAN [em FISHES WITH GILL-ARCH JAWS CAMBRIAN ? SOFT-SKINNED CHORDATES ORIGIN AND ADAPTIVE RADIATION OF THE AMPHIBIA W. K. GREGORY. 1916 RATIO 12, 18,000,000 YEARS PALAEOZOIC OF INVERTEBRATES EARLY PALAEOZOIC Fic 59. DESCENT oF THE AMPHIBIA The Amphibia—in which the fin is transformed into a limb (Thinopus)—are believed to have evolved from an ancestral ganoid fish stock of Silurian age through the fringe- finned ganoids. From this group diverge the ancestors of the Reptilia and the sala- mander-like Amphibia which give rise to the various salamander types, also to branches of limbless and snake-like forms (Aistopoda, modern Ccecilians). The other great branch of the solid-skulled Amphibia, the Stegocephalia, was widespread all over the northern continents in Permian and Triassic time (Cricotus, Eryops), and from this stock descended the modern frogs and toads (Anura). Prepared for the author by W. K. Gregory. pelled type of the modern salamander and newt. The large- headed, short-bodied types (Amphibamus) were precocious descendants of such primordial forms. In Upper Carbonifer- EVOLUTION OF THE AMPHIBIANS 179 ous and early Permian time the terrestrial amphibians began to be favored by the land elevation and recession of the sea which distinguished the close of the Carboniferous and early Permian time. Under these varied zonal conditions, aquatic, palustral, terrestrio-aquatic, fossorial, and terrestrial, the Am- EUMICRERPETON PTYONIUS AMPHIBIA CARBONIFEROUS re erinne CARBONIFEROUS, o ‘Yin fp aii SE Yel sell eas =e ‘9 " y)) AMPHIBAMUS DIPLOCAULUS AMPHIBIA CARBONIFEROUS AAMPHIBIA PERMO- CARBONIFEROUS Fic. 60. CHIEF AMPHIBIAN TYPES OF THE CARBONIFEROUS. Restorations of the early short-tailed, land-living Amphibamus, the salamander-like Eumicrerpeton, the eel-bodied Ptyonius, and the broad-headed, bottom-living Diplo- caulus. Prepared for the author by W. K. Gregory and Richard Deckert. phibia began to radiate into several habitat zones and adaptive phases, and thus to imitate the chief types of body form which had previously evolved among the fishes as well as to anticipate many of the types of body form which were to evolve subse- quently among the reptiles. One ancestral feature of the amphibians is a layer of superficial body scales in some types, which appear to be derived from those of their lobe-finned fish ancestors; with the loss of these scales most of the Amphibia also lost the power of forming a bony dermal armature. 180 THE ORIGIN AND EVOLUTION OF LIFE Recent researches in this country, chiefly by Williston, Case, and Moodie, indicate that the solid-headed Amphibia (Stegocephalia) and primary forms of the Reptilia chiefly be- long to late Carboniferous (Pennsylvania) and early Permian time. They are found abundantly in ancient pool deposits, which are now widespread over the southwestern United States and Europe deposited in rocks of a reddish color. This reddish color points to aridity of climate in the northern hemis- phere during the period in which the terrestrial adaptive radiation of the Amphibia occurred. Wie cant ; These arid conditions Fic. 61. SKULL AND VERTEBRAL COLUMN OF : ; Diplocaulus. continued during the A typical solid-, broad-headed amphibian from the Permian of northern Texas. Specimen in the American Museum of Natural History. (Com- time, especially in the pare Fig. 60.) greater part of Permian northern hemisphere. In the southern hemisphere there is evidence, on the con- trary, of a period of humidity, cold, and extensive glaciaticn, which was accompanied by the disappearance of the old lyco- pod flora (club-mosses) and arrival of the cool fern flora (Glos- sopteris), which appeared simultaneously in South America, South Africa, Australia, Tasmania, and southern India. The widespread distribution of this flora in the southern hemisphere furnishes one of the arguments for the existence of the great South Atlantic continent Gondwana, a transatlantic land bridge of animal and plant migration, postulated by Suess and sup- ported by the paleogeographic studies of Schuchert. In North America the glaciation of Permian time is believed to EVOLUTION OF THE AMPHIBIANS 181 have been only local. The last of the great Paleozoic seas dis- appeared from the surface of the continents, while the border seas give evidence of the rise of the ammonite cephalopods. Toward the close of Permian time the continent was com- pletely drained. Along the eastern seaboard the Appalachian EARLIEST. “F| PERMIAN. pekanne S| * 180 165 so BS zo to: Ss PALEOGEOGRAPHY, EARLIEST PERMIAN (LOWER ARTINSKIAN-ROTLIEGENDE-AUTUNIAN), A GLACIAL TIME AFTER SCHUCHERT, APRIL, 1916 Y MARINE DEPOSITS © CONTINENTAL DEPOSITS ifftice FIELDS T DIRECTION OF ICE FLOW == UNCERTAIN ICE FIELDS: x®*VOLCANOES = aaaaMOUNTAINS Fic. 62. THEORETIC WORLD ENVIRONMENT IN EARLIEST PERMIAN TIME. A period of marked glacial conditions in the Antarctic region. Vanishing of the coal floras and rise of the cycad-conifer floras, along with the rise of more modern insects and the beginning of the dominance of reptiles. Modified after Schuchert, 1916. revolution occurred, and the mountains rose to heights esti- mated at from three to five miles. An opposite extreme, of slender body structure, is found in the active predaceous types of water-loving amphibians such as Cricotus, of rapid movements, propelled by a long tail fin, and with sharp teeth adapted to seizing an actively moving prey. This type retrogresses into the eel-like, bottom-loving Lysorophus with its slender skull, elongate body propelled by 182 THE ORIGIN AND EVOLUTION OF LIFE lateral swimming undulations, the limbs relatively useless. Corresponding to the bottom-living fishes are the large, slug- gish, broad-headed, bottom-living amphibians, such as Dzplo- caulus, with heads heavily armored, limbs small and weak, the body propelled by lateral motions of the tail. There were also CRICOTUS PERMO- AMPHIBIA CARBONIFEROUS AMPHIBIA PERMO- CACCES CARBONIFEROUS IL me iS SSS PA Ss ¥ ‘| Pra Sy, 444 “in Z ws, ee é iS Se oe CONTINENTAL DEPOSITS iflltice Frevo f DIRECTION OF ICE FLOW == UNCERTAIN ICE FIELDS = x*" VOLCANOES) naan MOUNTAINS Fic. 65. THEORETIC WORLD ENVIRONMENT IN EARLIEST PERMIAN TIME. A period of marked glacial conditions in the Antarctic region. Vanishing of the coal floras and rise of the cycad-conifer floras, along with the rise of more modern insects and the beginning of the dominance of reptiles. Modified after Schuchert, 1916. type these pro-reptiles are different in the inner skeletal struc- ture and in the anatomy of the skull they are exclusively air-breathing, primarily terrestrial in habit rather than ter- restrio-aquatic, superior in their nervous reactions and in the development of all the sensory organs, and have a more highly perfected cold-blooded circulatory system. Neverthe- less, the most ancient solid-headed reptilian skull type (Cotylo- sauria, Pareiasauria, of Texas and South Africa, respectively) 186 THE ORIGIN AND EVOLUTION OF LIFE is very similar to that of the solid-headed Amphibia (Steg- - ocephalia). Bone by bone its parts indicate a common descent from the skull type of the fringe- finned fishes Hig 3. As revealed by the researches of Cope, Williston, and Case, the adaptive radiation of the (Crossopterygia, REPTILIA Nye CARBCNIRCROUS reptile life of western America in Permian time is as follows: First there is a variety of swift- moving, alert, predaceous forms corresponding to the fusiform, swift-moving stage in the evolu- fishes. these reptiles (Varanops) re- semble the modern monitor liz- “SS ARAEOSCELIS ily tion of the Some of E REPTILIA CARBONIFEROQUS Fic. 66. Two of the defenseless, swift-moving, ANCESTRAL REPTILIAN TYPES. terrestrial reptilian types, Varanops and Ar@oscelis, of the Permo-Carbonif- erous period of Texas. The skull and skeleton of Are@oscelis foreshadow the existing lizard (Lacertilian) type and Williston regards it as the most nearly related Permian representative known of the true Squamata (ancestors of ards (Varanus); others (Ophi- acodon and Theropleura) are provided with four well-devel- oped limbs and feet, the long tail being utilized as a balancing the lizards, snakes, and mosasaurs). Restorations of Varanops and Ar@os- celis modified from Williston. Drawn for the author by Richard Deckert. organ. ‘These were littoral or lowland reptiles, insectivorous The primitive, lizard-like pelycosaur Varanops, with a long tail or carnivorous in habit. and four limbs of equal proportions, represents more nearly than any known ancient reptile, apart from certain special characters, a generalized prototype from which all the eighteen Orders of the Reptilia might have descended; its structure could well be ancestral to that of the lizards, the alligators, and the dinosaurs. At present, however, it is not determined whether EARLIEST REPTILES 187 the primitive ancestors from which the various orders of reptiles descended belong to a single, a double, or a multiple stock. Passing to the widely different amphibian-like order known as cotylosaurs, we see animals which, on the one hand, grade into the more fully aquatic, pad- dle-footed, free-swimming Lim- noscelis with a short, crocodile- like head, which propelled itself by means of its long tail, and, on the other hand, there devel- oped short-tailed, semi-aquatic forms, such as the Labido- saurus. In adaptation to the more purely terrestrial habitats there is sometimes a reduction in the length of the tail and greater perfection in the struc- ture of the limbs and the various forms of armature. In Pantylus these defenses appear in the form of bony ossicles of the skin and scutes; in Chilonyx the skull top is covered with tuber- culated defenses; in the slow- moving Diadectes the body is partly armored, the animal be- ing proportioned like the exist- ing Gila monster and probably of nocturnal habits, which is in- ferred from the large size of the eyes. LABIDOSAURUS ERMO- REPTILIA CARBONIFEROUS PERMO- REPTILIA SEYMOURIA CARBONIFEROUS DIADECTES PERMO- REPTILIA CARBONIFEROUS Fic. 67. REPTILES WITH SKULLS TRANS- ITIONAL IN STRUCTURE FROM THE AMPHIBIAN SKULL. Typical solid-headed reptiles (Coty- losaurs) characteristic of Permo-Car- boniferous time in northern Texas, including the three forms Seymourta, Labidosaurus, and the powerful Dia- dectes, which resembles the existing Gila monster. The head in the mounted skeleton of Diadectes (lower) in the American Museum of Natural History is probably bent too sharply on the neck. Restorations for the author by W. K. Gregory and Richard Deckert. Labidosaurus and Seymouria chiefly after Williston. 188 THE ORIGIN AND EVOLUTION OF LIFE The most remarkable types in this complex reptilian society of Permian Texas are the giant fin-backed lizards, Clepsydrops, Dimetrodon, Edaphosaurus, of Cope, probably terrestrial and carnivorous in habit. In these animals the neural spines of the dorsal vertebre are vertically elongated to support a power- ful median membranous fin, the spines of which are sometimes MIDDLE PERMIAN PALEOGEOGRAPHY, MIDDLE PERMIAN (THURINGIAN-ZECHSTEIN) TIME AFTER SCHUCHERT, APRIL, 1916 MO MARINE DEPOSITS A CONTINENTAL DEPOSITS — fff) GYPSUM AND SALT — ana’ MOUNTAINS vy GONDWANA FLORA Fic. 68. THEORETIC WORLD ENVIRONMENT IN MIDDLE PERMIAN TIME. Great extension of the Baltic Sea and of the Eurasiatic Mediterranean Tethys. Rise of the Appalachian, Northern European Alps, and many other mountains. Modified after Schuchert. smooth (Dimetrodon), sometimes provided with transverse rods (Edaphosaurus cruciger). These structures may have devel- oped through social or racial competition and selection within this reptile family rather than as offensive or defensive organs in relation to other reptile families. We now glance at the Permian life of another great zoologic region. Africa has been throughout all geologic time the most stable of the continents, especially since the begin- EARLIEST REPTILES 189 ning of the Permian Epoch. The contemporaneous evo- lution of the pro-Reptilia, traced in a continuous earth section from the base of the Permian to the Lower Trias- sic, aS successively explored Dye balla Owelies oceley, Broom, and Watson, has re- realed a far more extensive and more varied adaptive radiation of the reptiles than that which is known on the American continent. Al- though the adaptations are chiefly terrestrial, we trace ~ ! certain strong analogies if not actual relationships to the Permo-Triassic reptiles of North America. While the drying pools and lagoons of arid North America were entombing the lifes of — the Permian . and Triassic Epochs, there were being deposited in the Karoo series of South Africa some 9,500 feet of strata consist- ing of shales and sandstones, chiefly of river flood-plain and delta origin, and rang- ing in time from the basal EDAPHOSAURUS PERMO- REPTILIA CARBONIFEROUS DIMETRODON PERMO- REPTILIA CARBONIFEROUS Fic. 69. THe FIN-BACK PERMIAN REPTILES. Restorations (middle and upper figures) of the giant carnivorous reptiles of northern Texas in Permian time; the large-headed Dimetrodon and the contemporary small- headed Edaphosaurus cruciger. In both animals the neural spines of the vertebre are greatly elongated, hence the popular name ‘“‘fin-back.” Skeleton of Dimetrodon (lower) in the American Museum of Natural History. Restorations for the author by W. K. Gregory and Richard Deckert. 1QO THE ORIGIN AND EVOLUTION OF LIFE Permian into the Upper Triassic. Here, up to the year Igo, twenty-two species of fossil fishes had been recorded, mostly ganoids of Triassic age. The eleven species of amphibians dis- covered are of the solid-headed (Stegocephalia) type, broadly similar in external appearance to those of the same age discovered in Europe. The one hundred and fifteen species of reptiles described from the Lower and Middle Per- otha pans pe mian deposits include solid-headed pareiasaurs—great, round-bodied, herbivorous reptiles with massive ICTIDOPSIS REPTILIA TRIASSIC limbs and round heads—which are allied to the cotylosaurs of the Permo-Carboniferous of America, the agile dromosaurs, similar to the lizard-like reptiles of the Texas CYNOGNATHUS REPTILIA TRIASSIC Fic. 70. MAMMAL-LIKE REPTILES OF Permian, with large eye-sockets, Sour AFRICA, and adapted to swift, cursorial The relative stability of the African movements, also reptiles known continent favored the early evolu- tion of the free-limbed forms of as therocephalians in reference to reptiles known as Anomodonts, in- ; cluding the powerful Endothiodon, the analogy which the skull bears in which the jaws are sheathed in a horn like those of turtles; and also se that of the mammals, peeked: of the Cynodonts (dog-toothed sians, and numerous slender - reptiles), including the carnivorous, ; ; : strongly toothed Cynognathus which limbed, predatory reptiles with iswalied “to, the vancestorspolatheeecharp cannon teeth am be ian Mammalia. Restorations for the er . author by W. K. Gregory and predaceous Reptilia of the time Richard Deckert. : ; : ‘c ° are the dinocephalians (7. e., ‘‘ terri- ble-headed’’), very massive animals with a highly arched back, broad, swollen forehead, short, wide jaws provided with mar- ginal teeth. Surpassing these in size are the anomodonts (7. e., “lawless-toothed”’) in which the skull ranges from a couple MAMMAL-LIKE REPTILES 191 of inches to a yard in length, and the toothless jaws are sheathed in horn and beaked like those of turtles. This is a nearly typical social group: large and small, herbivorous, omnivorous, and carnivorous, toothed, toothless and horny-beaked, swift- moving, slow-moving, unarmored, partly armored; it lacks only the completely armored, slow-moving type to be a perfect complex. In the Upper Permian the fauna includes pareiasaurs and gorganopsians, which are similar to a large group of reptiles of the same geologic age discovered in Russia by Amalitzky. In Lower and Middle Triassic time the last and most highly specialized of the beaked anomodonts appear together with di- minished survivors (Procolophon) of the very ancient solid-headed order (Pareiasauria of South Africa, Cotylosauria of Texas). Here also are found the true cynodonts, which are the most mammal-like of all known reptiles. In the Upper Triassic of South Africa occur carnivorous dinosaurs, also crocodile-like phy- tosaurs (Fig. 75), allied to those of Europe and North America. ORIGIN OF THE MAMMALS AND ADAPTIVE RADIATION OF THE EIGHTEEN ORDERS OF REPTILES The most notable element in this complex reptilian society of South Africa are those remarkable pro-mammalian types of reptiles (cynodont, theriodont), from which our own most remote ancestors, the stem forms of the Mammalia, the next higher class of vertebrates above the Reptilia, were destined to arise. This is another instance where paleontology has dis- lodged a descent theory based upon anatomy, for at one time from anatomical evidence alone Huxley was disposed to derive the mammals directly from the amphibians. The question at once arises, why were these particular reptiles so highly favored as to become the potential ancestors of the 192 THE ORIGIN AND EVOLUTION OF LIFE mammals? At least two reasons are apparent. First, these larger and smaller types of South African pro-mammals exhibit an exceptional evolution of the four limbs, enabling them to travel with relative rapidity, which is connected with ability to migrate, powers doubtless associated with increasing in- telligence. Another marked characteristic which favors de- velopment of intelligence is the adaptability of their teeth to different kinds of food, insectivorous, carnivorous, and herbiv- orous, which leads to development and diversity of the powers of observation and choice. In this adaptability they in a limited degree anticipate the evo- lution of the mammals, for the other erineen mae reptiles generally are distinguished by a REPTILIA PERMIAN ; : : ° singular arrest or inertia in tooth de- Fic. 71. A SoutH AFRICAN - oa ; “Dog-Toornen” Repmme. Velopment. Rapid specialization of the Head of one of the South teeth is one of the chief features in the African Cynodonts or “dog- : : : toothed” reptiles, related to history of the mammals, which display the sane cstors | Of eames ea continuous moment Mieaomad vane mals. Restoration for the _ : t author by W. K. Gregory in tooth structure, associated with pata dh ee specialization of the organs of taste. Of greater importance in its influence on the brain evolu- tion of the early pro-mammalian forms is the internal tem- perature change, whereby a cold-blooded, scaly reptile is transformed into a warm-blooded mammal through a change which produced the four-chambered heart and complete sep- aration of the arterial and venous circulation. This change may have been initiated in some of the cynodonts. This new constant and higher temperature favors the nervous evolution of the mammals but has no influence whatever upon the me- chanical evolution. As pure mechanisms the cold-blooded rep- tiles exhibit as great plasticity, as great diversity, and perhaps ADAPTIVE RADIATION OF REPTILES 103 higher stages of perfection than the mammals. Nor does increas- ing intelligence, as we shall see, favor mechanical perfection. Turning our survey to the origin and adaptive radiation of the reptiles as a whole, we find that in Permian time all of the 3 TUATARA SEE __ ___CROCOD “ey S (SPHENODON) Bae is } S| 2 | Ay ~ MARSUPIAL A AAA BX , =~ MAMMALS y : HAE CRETACEOUS FAN Y, j HAA 4 4 E (6) 4 ZR. S Hie Y “2 r—_ \) Z US Py ahi kt fo Fe Zu ¥ i tA A oO FA i HA BZ N CRETACEOUS eal: = YX | HA EY &£ (COMANCHEAN) _ 1 H } A BAB ; Z “PRIMITIVE HH BY croco JURASSIC i Z MAMMALS ; HH Ff = Senge be an oo ese y eae B fee ll VE? Ve aes. 1 Frmasse | RTLES ICHTHYO- ———~PLESIO- : RHYNCHO- PALIG- FIR} P PRQGCOLO- SAYRS SAUrS ‘fev CEPHS UANA DIN Ss eon d 4 MO- eS a ee ee Kaeo Bt Z DEUTERO! Bours ae By Al -ARAEOSCELIS First 7 < [Perwan —|Enonus. COTYLO-___ PROGANO- NSAURS MAMMAL-LIKEZ_|___ recyé PROTOROSAURS DIAPSIOD REPTILES =~ PENNSYLVANIAN SAURS SAURS sTOCkKA shits CARBONInEnOUS) ee err vf MISSISSIPPIAN FIRST REPTILES CARBENIFEROUS) DEVONIAN FIRST AMPHIBIANS FIRST FISHES | SATA AS TD MA uekts OPREVERTEBRATES Sn) 7 LEGON FELL: Ge Ge fain, WR CAMBRIAN PALAEOZOIC EARLY PALAEOZOIC “ORIGIN AND ADAPTIVE RADIATION OF THE REPTILES w.xcnecony, i916 Fic. 72. ADAPTIVE RADIATION OF THE REPTILIA. The reptiles first appear in Upper Carboniferous and Lower Permian time and radiate into eighteen different orders, three of which—the Cotylosaurs, Anomodonts, and Pely- cosaurs—attain their full evolution in Permian and Triassic time and later become extinct. Six orders—the Ichthyosaurs, Plesiosaurs, Dinosaurs, Phytosaurs, Pterosaurs, and Turtles—are first discovered in Triassic time, while five of the orders—the Ich- thyosaurs, Plesiosaurs, Mosasaurs, Dinosaurs, and Pterosaurs—dominate the Cretace- ous Period and become suddenly extinct at its close, leaving the five surviving modern orders—Testudinata (turtles, tortoises), Rhyncocephalia (tuateras), Lacertilia (lizards), Ophidia (snakes), and Crocodilia (crocodiles). These great reptilian dynasties: seem to have extended over the estimated ten million years of the Mesozoic Era, namely, the Triassic, Jurassic, and Upper Cretaceous Epochs. Prepared for the author by W. K. Gregory. ten early adaptive branches of the reptilian stem had radiated and become established as prototypes and ancestors of the great Mesozoic Reptilia. Five divisions, namely, the coty- losaurs, anomodonts, pelycosaurs, proganosaurs, and phyto- saurs, were destined to become extinct in Permian or Triassic time, in each instance as the penalty of excessive and prema- 194 THE ORIGIN AND EVOLUTION OF LIFE ture specialization. Five other great branches, namely, the ichthyosaurs, plesiosaurs, two great branches of the dinosaurs, and the pterosaurs, were destined to dominate the waters, the earth, and the air during the Mesozoic Era, 7. e., the Tri- assic, Jurassic, and Cretaceous Epochs. ‘Thus altogether thir- teen great branches of the reptilian stock became extinct either before or near the close of the Age of Reptiles. Out of the total of eighteen reptilian branches only five were destined to survive into Tertiary time, namely, the orders which include the existing turtles, tuateras, lizards, snakes, and crocodiles. GEOLOGIC BLANKS AND VISTAS OF REPTILIAN EVOLUTION As pointed out in the introduction of this chapter, the rep- tile ancestor of these eighteen branches of the class Reptilia— a class with an adaptive radiation which represents the mechan- ical conquest of every one of the great life zones, from the aérial to the deep sea—will some day be discovered as a small, lizard- like, cold-blooded, egg-laying, four-limbed, long-tailed terres- trial form, with a solid skull roof, of carnivorous or more prob- ably insectivorous habit, which lived somewhere on the land surfaces of Carboniferous time. Such undoubtedly was the reptilian prototype from which evolved every one of the marvellous mechanical types which we may now briefly re- view. By methods first clearly enunciated by Huxley in 1880 several of the ideal vertebrate prototypes have been theoreti- cally reconstructed, and in more than one instance discovery has confirmed these hypothetical reconstructions. The early geologic vistas of this entire radiation are seen in the reptilian life of the Permian Epoch of North America, Europe, and Africa just described, consisting exclusively of ter- restrial and terrestrio-aquatic forms. In the Triassic we obtain succeeding vistas of the terrestrial and fluviatile life of North ADAPTIVE RADIATION OF REPTILES 195 America, Europe, and Africa, as well as our first glimpses of the early marine life of North America. In Jurassic time deposits at the bottom of the great interior continental seas give us the TERRESTRIAL AND FLUVIATILE MARINE N. AMER. | EUROPE | AFRICA |S. AMER. |N. AMER. | EUROPE | AFRICA: | Ss. AMER. — Tees Sees QUATERNARY | | | | | Se oes i eae se eet ae TERTIARY | | | l | | LZzmz2£:b 222 22£££LL£=_LZ_L-£—LLLLL__L_L—_ _ FINAL pines aoe FINAL REPTILIAN SEA FAUNA UPPER G7 (PREDENTATA AND THEROPODA) GZ ZZ ig ALAA £ZA LOWER CRETACEOUS | ZZ. (COMANCHEAN) Z Zz zzzAD TAGESM7,_—— EZ el SIDI: pte, fae A 7" 7"-7-ZZ- | SG teeic LZ2 4 7-7" SECOND REPTILIAN SEA FAUNA (PLESIOSAURS AND ICHTHYOSAURS) ; | aaa Aa ek 2 Dt EE heal ZZ ST DINOSAUR STAGES L777 ee ahd a. TRIASSIC A IVE DINOSAURS) ZA PRIMITIVE ICHTHYOSAURS) g LAAZLZZZDZ ZAZA ZA Fic. 73. Grotoctc REcoRDS OF REPTILIAN EVOLUTION, TERRESTRIAL AND MARINE. Shaded areas represent the geologic vistas of reptilian life which have been discovered from fossils entombed in ancient TERRESTRIAL, FLUVIATILE, and MARINE habitats of different portions of the northern and southern hemispheres. Triassic. We begin with the deposits of the continental surfaces of North America, Europe, and Africa. During Triassic time the FIRST DINOSAUR STAGES appear, as well as some of the semi-aquatic forms which frequented fluviatile regions, while the PRrr- TIVE ICHTHYOSAURS were then fully adapted to marine life. Jurassic and Lower CRETACEOUS. We continue with geologic vistas of the succeeding marine life and the evolution of the SECOND REPTILIAN SEA FAUNA, indicated by the shaded areas of the Jurassic and the Lower Cretaceous of North America and Europe. The remains of these animals are found in the deposits of deep or shallow sea waters. There is one great vista, the SECOND DINOSAUR STAGES, which includes the terrestrial dinosaurs known as SAUROPODA, found in Upper Jurassic and Lower Cretaceous de- posits in North America, Europe, Africa, and South America. Upper CRETACEOUS. Then there was a long interval, followed by the FINAL DINOSAUR STAGES and a long vista of the terrestrial reptilian life of Upper Cretaceous time, especi- ally in North America. Contemporary with this is the FINAL REPTILIAN SEA FAUNA. Chart by the author. second reptilian sea fauna of plesiosaurs and ichthyosaurs within the continents of North America and Europe. The story of the marine pelagic evolution of the reptiles is continued with some interruptions through the Lower Cretaceous into the final rep- 196 THE ORIGIN AND EVOLUTION OF LIFE tilian sea fauna of plesiosaurs and mosasaurs of Upper Creta- ceous time. In the meanwhile the life of the continents is revealed in the terrestrial and fluviatile deposits of the Triassic Epoch, in the first stages of the terrestrial evolution of the dinosaurs, in the early stages of the fluviatile evolution of the Crocodilia, and in the final stages of the terrestrial phases of the Amphibia and pro-Reptilia. A long interval of time elapses at this period in the earth’s history, during which the life of the con- tinents is entirely unknown, until the close of the Jurassic and beginning of Cretaceous time, when there appears a sec- ond great stage of dinosaur evolution, revealed especially in the lagoon deposits of North Africa and South America, which have yielded remains of giant Sauropoda. Then another gap occurs in the story as told by continental deposits. Finally, in Upper Cretaceous time we again discover great flood-plain and shore-line deposits, which give a prolonged vista of the ter- restrial life of the Reptilia, especially in North America and Europe. Thus it will be understood that, while the great tree of reptilian descent has been worked out through a century of scientific researches, beginning with those of Cuvier and con- tinued by Owen, Leidy, Cope, Marsh, and our contemporary paleontologists, there are enormous gaps in both the terres- trial and the marine history of several of the reptilian orders which remain to be filled by future exploration. We piece to- gether fossil history on the continents and in the seas from the animals entombed in these deposits, partly by means of the real relationships observed in widely migrating forms, such as the land dinosaurs and the marine ichthyosaurs, ple- slosaurs, and mosasaurs. Many of these reptiles ranged over every continent and in every sea. On the whole, the physio- ADAPTIVE RADIATION. OF- REPTILES 197 graphic condition most favorable to the preservation of life in the fossil condition is that known as the flood-plain, in which the rising waters and sediments of the rainy season rapidly entomb animal remains which are deposited on the surface Anderson Phot 1996 Fic. 74. CLOSE OF THE AGE OF REPTILES. A RELIC OF ANCIENT FLOOD-PLAIN CONDI- TIONS. Iguanodont dinosaur lying upon its back. Integument impressions preserved. The “dinosaur mummy,” Trachodon, from the Upper Cretaceous flood-plain deposits of Converse County, Wyoming. Due to arid seasonal desiccation, the skin folds and impressions are preserved over the greater part of the body and limbs. Discovered by Sternberg. Mounted specimen in the American Museum of Natural History. or in small water pools during the drier seasons. Fossils buried in old flood-plain areas of South Africa tell us the story of the life evolution which is continued by the ancient shore and lagoon deposits in other parts of the world as well as by fossils found in the broad, intermittent flood-plain areas of the American Triassic and Cretaceous, which close with the 198 THE ORIGIN AND EVOLUTION OF LIFE great delta deposits of the Upper Cretaceous lying to the east of the present Rocky Mountain range. The more re- stricted deposition areas of drying pools and lagoons, such as those observed in the Permian and Triassic shales and sand- stones of Texas, entomb many forms of terrestrial life. Vistas of the contemporaneous evolution of fluviatile, aquatic, and marine life are afforded by the animals which perish at the surface and sink to the calcareous bottom oozes of the conti- nental seas of Triassic, Jurassic, and Cretaceous time. It is only in the Tertiary of the Rocky Mountain region of North America that we obtain a nearly continuous and uninterrupted storv of the successive forms of continental life, among the mammals entombed in the ancient flood-plains, in the volcanic ash-beds, in the lagoons, and more rarely in the littoral deposits. AQUATIC ADAPTATION OF THE REPTILIA, DIRECT AND REVERSED From the distinctively terrestrial radiations of Permian time we turn to the development of aquatic habitat phases among the reptiles which lived along the borders of the great interior rivers and continental seas of Permian, Triassic, and Jurassic time. This reversal of adaptation from terrestrial into aquatic life is, as we might theoretically anticipate, a reversal of func- tion rather than of structure, because, as above stated (p. 159), it 1s a universal law of form evolution that ancient adaptive characters once lost by the heredity-chromatin are never reacquired. In geologic race evolution there is no process analogous to the wonderful phenomena of individual regenera- tion or regrowth, such as is seen among amphibians and other primitive vertebrates, whereby the original limb may be com- pletely restored from the mutilated remnant of an amputation. AQUATIC REPTILES 199 Such regeneration is attributable to the potentiality of the heredity-chromatin which still resides in the cells of the am- putated surfaces. ‘The heredity-chromatin determiners of the bones of the separate digits or separate phalanges if once lost in geologic time are never reacquired; on the contrary, each phase of habitat adapta- tion is forced to commence with the elements remain- ing in the organism’s hered- ity-chromatin, which may REPTILIA fe cnn eus have been impoverished in previous habitats. When an ancient habitat zone is reentered there must be readaptation of the parts Peotc he erm alin | US s ue a en TRIASSIC when the terrestrial rep- Fic. 75. Reprires LEAVING A TERRESTRIAL 5 ie ; FOR AN AQUATIC HABITAT, THE BEGINNING tect cen Cl tNeCraqualic or Aquatic ADAPTATION. zone of their amphibian _ Littoral-fluviatile types independently evolve in the Triassic (Rhytidodon, a phytosaur) and ancestors they cannot re- in the Upper Cretaceous (Champsosaurus). sume the amphibian char- These animals belong to two widely different orders of reptiles, neither of which is closely acters, for these have been akin to the modern alligators and crocodiles. : The adaptation is convergent to that of the lost by the chromatin. existing gavials and crocodiles. Restorations This invariable princi- for the author by W. K. Gregory and Richard Deckert. ple underlying reversed evolution is partly illustrated (Fig. 53) in the passage from the reptilian foot into the fin of the aquatic reptile and with equal clearness in the passage of the wing of the flying bird into the fin of the swimming bird (Fig. 110). In no less than eleven out of the eighteen orders of reptiles reversed adaptation to a renewal of aquatic life, like that of the fishes and amphibians, took place in the long and slow 200 THE ORIGIN AND YY) REPTILIA eM Re NOME Ls TRIASSIC GEOSAURUS REPTILIA JURASSIC REPTILIA TYLOSAURUS SRELOCE Us CRICOTUS PERMO- AMPHIBIA CARBONIFEROUS . Fic. 76. CONVERGENT AQuaTic ADAP- TATION INTO ELONGATE FUSIFORM TYPE IN Four DIFFERENT ORDERS OF AMPHIBIANS AND REPTILES. Independently convergent evolution of four long- bodied, free-swimming, swift-moving, surface-liv- - jng aquatic types in which the fins and limbs are retained as paddles: Cricotus, an amphibian; Ty- losaurus, an Upper Cretaceous mosasaur; Geo- saurus, a Jurassic crocodilian; Cymbospondylus, a Triassic ichthyosaur. A very similar fusiform type evolves among the mammals in the Eocene ceta- ceans (Zeuglodon), as seen in Fig. 123. Restora- tions prepared for the author, independent of scale, by W. K. Gregory and Richard Deckert. EVOLUTION OF LIFE passage from a terrestrial phase, through palustral, swamp-living phases into a littoral, fluviatile phase, and from this into littoral and marine salt-water phases; so that finally in no less than six orders of reptiles the pelagic phase of the high seas was inde- pendently reached. The role in the economy of oceanic life which is now taken by the whales, dolphins, and por- poises was assumed by families of the plesiosaurs, ichthyosaurs, mosasaurs, snakes, and croco- diles, all flourishing in the high seas, together with families of the turtles, which are the only high-sea reptiles surviving at the present day. Moreover, under the alternating adaptations to terrestrial and marine life, which prevailed during the 10,000,000 years of late Paleozoic and Mesozoic time, several families of the existing orders of reptiles sought a seafaring existence more than once and gave off numerous side branches from the main stem. The adapta- tions to marine life have been especially studied by Fraas. 201 AQUATIC REPTILES Even to-day there are tendencies toward marine invasion observed among several of the surviving families of lizards and crocodiles of seashore frequenting habits. NN AY rE Un | LA, YY, vIHONsvuvd KOs | | LF Or | | ry cal oD BAW VITWH4300HONAHY KOniiiin™ | PAN Yo Ky yy iro» : SS K€ vidio —ODe Cea | ViTlL430V1 TS or | | \ VIUNVSONVSOUd {\ (\UUME MA : i. ‘TTT, | cre ———aaEa=7=~= | yimiao00¥9 momen Sy, | VIUNYSOAHLHOI KIO | } NIN Nes sunvsolstid {UI —————— 7 p | -_~ ADAPTIVE RADIATION OF AQUATIC REPTILES PALUDAL (SWAMP LIVING LITTORAL- MARINE (SALT WATER) | | | | | | | | TERRESTRIAL (LAND LIVING FLUVIATILE (FRESH WATER) LITTORAL- This final Nine of INDEPENDENT REVERSED ADAPTATION TO THE AQUATIC ZONES IN TWELVE ORDERS OF REPTILES, ORIGINATING ON LAND AND ENTERING THE SEAS. Chelonia (sea-tortoises), ichthyosaurs, mosasaurs (marine lizards), crocodiles, and the reptilian orders give off not only one but from two to five independent branches seeking aquatic life, of which six independently reach the full pelagic high-sea phase. Still more remarkable than the law of reversed adaptation marine pelagic phase of evolution is attained in only six orders, namely, the plesiosaurs, certain ophidians (true sea-snakes found far out at sea in the Indian Ocean). into the littoral-fluviatile (fresh-water and brackish-water) zone, thence into the littoral- from the terrestrial (land-living) zone into the paludal (swamp-frequenting) zone, thence marine (salt-water) zone, and finally into the pelagic zones of the high seas. Diagram showing the manner in which twelve of the eighteen orders of reptiles descend is that of alternate adaptation, which has been brilliantly Pigie 7%: 202 THE ORIGIN AND EVOLUTION OF LIFE developed by Louis Dollo, of Brussels. This is applied hypo- thetically to the evolution of the existing leatherbacks (Sphar- 7 ANCESTRAL CHELONIANS TERR2 AQUATIC WITH SOLID CARAPACE ® AND PLASTRON AQUATIC, FLUVLE PRIMARY LITTORAL STAGE WITH UNIMPAIRED CARAPACE AND PLASTRON PRIMARY PELAGIC STAGE WITH CARAPACE AND PLASTRON PROGRESSIVELY ATROPHIED » — ABYSSAL 4\| SECONDARY LITTORAL STAGE PRIMARY CARAPACE AND PLASTRON REDUCED A SECONDARY CARAPACE AND PLA SECONDARY PELAGIC STAGE SECONDARY CARAPACE REGRESSIVE SECONDARY PLASTRON REDUCED Fic. 78. CHELONIA. DIAGRAM ILLUSTRATING THE ALTERNATE HABITAT MIGRATION OF THE ANCESTRAL ‘“ LEATHERBACKS,” SPHARGID&. Dollo’s theory is that these animals originate in armored land forms with a solid bony shell, and pass from the terrestrio-aquatic into the littoral and then into the pelagic zone, in which the solid bony shell, being no longer of use, is gradually atrophied. After prolonged marine pelagic existence these animals return secondarily to the littoral zone and acquire a new armature of rounded dermal ossicles which develop on the upper and lower shields of the body. The animals (Sphargis) then for a second time take up existence in the pelagic zone, during which the dermal ossicles again tend to disappear. gid), an extremely specialized type of sea turtles. It is be- lieved that after a long period of primary terrestrial evolution Fic. 79. THE Existinc “LEATHERBACK” CHELONIAN Sphargis. In this form the solid armature adapted to a former terrestrial existence is being replaced by a leathery shield in which are embedded small polygonal ossicles. After Lydekker. in which the ancestors of these turtles acquired a firm, bony carapace for land de- fense, they then passed through various transitions into a primary marine phase during which they gradually lost all their first bony arma- ture. Following this sea phase the animals returned to shore and entered a secondary littoral, shore-liv- ing phase, also of long dur- ation, in course of which they developed a second bony armature quite distinct in plan and pattern from the first. AQUATICORE PE EEGES 203 Descendants of these secondarily armored, shore-living types again sought the sea and entered a secondary marine pelagic phase in course of which they lost the greater part of their ARCHELON R REPTILIA Be TAGH Uae REPTILIA PLACOCHELYS TRIASSIC Fic. 80. ARMORED TERRESTRIAL CHELONIA INVADE THE SEAS AND LOSE THEIR ARMA- TURE. Convergent or analogous evolution (two upper figures) in the inland seas of the paddle-propelled chelonian Archelon (after Williston), the gigantic marine turtle of the Upper Cretaceous continental seas of North America, and of Placochelys (after Jaekel in part), a Triassic reptile belonging to the entirely distinct order Placodontia. Skeleton of Archelon (lower) in which the bony armature of the carapace has largely disappeared, exposing the ribs. Specimen in the Peabody Museum of Yale Univer- sity. After Wieland. second armature and acquired their present leathery covering, to which the popular name “leatherbacks”’ applies.’ In general the law of reversed aquatic adaptation is most brilliantly illustrated in the fossil ichthyosaurs, in the internal 1 This law of alternate adaptation may be regarded as absolutely established in the case of certain land-living marsupials in which anatomical records remain of an alterna- tion of adaptations from the terrestrial to the arboreal phase, from an arboreal into a secondary terrestrial phase, and from this terrestrial repetition to a secondary arboreal phase. The relics of successive adaptations to alternations of habitat zones and adap- tive phases are clearly observed in the so-called tree kangaroos (Dendrolagus) of Australia. 204 THE ORIGIN AND EVOLUTION OF LIFE anatomy of which land-living ancestry is clearly written, while reversed adaptation for marine pelagic life has resulted in a superficial type of body which presents close analogies to that of the sharks, porpoises, and shark-dolphins (Fig. 41). Integu- mentary median and tail fins precisely similar to those of the Fic. 81. ExTREME ADAPTATION OF THE ICHTHYOSAURS TO MARINE PELAGIC LIFE. Although primarily of terrestrial origin the ichthyosaurs become quite independent of the shores through the viviparous birth of the young as evidenced by a fossil female ichthyosaur (upper figures) with the foetal skeletons of seven young ichthyosaurs within or near the abdominal cavity. A fossil ichthyosaur (lower figure) with preserved body integument and fin outlines re- sembling those of the sharks and dolphins (see Fig. 41). Both specimens in the American Museum of Natural History from Holzmiden, Wiirtem- berg. sharks evolve, the anterior lateral limbs are secondarily con- verted into fin-paddles, which are externally similar to those of sharks and dolphins, while the posterior limbs are reduced. As in the shark, the tail fin is vertical, while in the dolphin the tail fin is horizontal. In the early history of their marine pelagic existence the ichthyosaurs undoubtedly returned to shore to deposit their eggs, but a climax of imitation of the dol- phins and of certain of the sharks is reached in the develop- ment of the power of viviparity, the growth of the young within AQUATIC REPTILES 205 the body cavity of the mother, resulting in the young ichthyo- saurs being born in the water fully formed and able to take care of themselves immediately after birth like the young of modern whales and dolphins. When this viviparous habit finally released the ichthyosaurs from the necessity of return- ing to land for breeding they developed the extraordinary powers of migration which car- ried them into the Arctic seas of Spitzbergen, the Cordilleran seas of western North America, and doubtless into the Antarc- tic. So far as we know this viviparous habit was never de- veloped among the seafaring turtles, which always return YM Pi REPTILIA udeerhd els eu TRIASSIC to shore to deposit their eggs. Fic. 82. RESTORATIONS oF Two Icu- While the ichthyosaurs vary SRM EL ASS hha 5 ai t Cymbospondylus, a primitive ichthyosaur great y lM SIZE, Cy present a from the Triassic seas of Nevada (after reversed evolution from the ter- Merriam), and the highly specialized Baptanodon, a Cretaceous ichthyosaur restrial, quadrupedal type into of the seas of that period in the region th ce . eqn hod of Wyoming, in which the teeth are € swilt-moving, fusiorm body greatly reduced. Restorations for the type of the fishes. which is author by W. K. Gregory and Richard ae Deckert. finally reduced in predaceous power through the degeneration of the teeth, as observed in the Baptanodon, an ichthyosaur of the Upper Jurassic seas of the ancient Rocky Mountain region. While the continental seas of Jurassic time were favorable to this remarkable aquatic marine phase of the reptiles, still greater inundations both of North America and of Europe occurred during Upper Cretaceous time. This was the period of the maximum evolution of the sea reptiles, the ultimate food supply of which was the surface life of the oceans, the 206 THE ORIGIN AND EVOLUTION OF LIFE marine Protozoa, skeletons of which were depositing the great chalk beds of Europe and of western North America. ; The Plesiosaurs had begun their invasion of the sea during Upper Triassic time, as shown in the primitive half-lizard Fic. 83. NortTH AMERICA IN UPPER CRETACEOUS TIME. The great inland continental sea extending from the Gulf to the Arctic Ocean, was favor- able to the evolution of the mosasaurs, plesiosaurs, and giant sea turtles (Archelon). This period is marked by the greatest inundation of North America during Mesozoic time, by mountains slowly rising along the Pacific coast from Mexico to Alaska, and by volcanic activity in Antillia. Detail from the globe model in the American Museum by Chester A. Reeds and George Robertson, after Schuchert. Lariosaurus, discovered in northern Italy, which still retains its original lacertilian appearance, due to the fact that the limbs and feet are not as yet transformed into paddles. In the subsequent evolution of paddles the number of digits re- mains the same, namely, five, but the number of the phalanges on each digit is greatly increased through the process known as hyperphalangy, an example of the numerical addition of AQUATIC REPTILES 207 new characters. Propulsion through the water was rather by means of the paddles than by the combined lateral body-and- Fic. 84. CONVERGENT Forms oF AQUATIC REPTILES OF DIFFERENT ORIGIN. Lariosaurus (left), the Triassic ancestor of the plesiosaurs from northern Italy, and Mesosaurus (right), from the Permian of Brazil and South Africa, representing another extinct order of the Reptilia, the Proganosauria. Drawn by Deckert after McGregor. tail motion seen among the ichthyosaurs, because all plesiosaurs exhibit a more or less abbreviated tail and a more or less broadly depressed body. It is also significant that the fore f Mac bibeea dicta i Ve NS Fic. 85. A PLESIOSAUR FROM THE JURASSIC OF ENGLAND. Skeleton of Cryptocleidus oxoniensis seen from above. Mounted in the American Museum of Natural History. 208 THE ORIGIN AND EVOLUTION OF LIFE and hind paddles are homodynamic, 7. e., exerting equal power; they are so exactly alike that it is very difficult to distinguish them, whether they are provided with four broad paddles or with four long, narrow, slender paddles. The plesiosaurs L —— = ——= CRETACEQUS TRINACROMERION CRETACEOUS REPTILIA FiG..286; PLESIOSAURS OF THE AMERICAN CON- TINENTAL CRETACEOUS SEAS. TYPES OF MARINE PELAGIC The slow-moving, long-necked Elasmo- saurus and the swift-moving, short- necked Trinacromerion. ‘The limbs are completely transformed into pad- dles. The great differences in the pro- portions of the neck and body repre- sent adaptations to greater or less speed. Restorations for the author by W. K. Gregory and Richard Deckert, chiefly after Williston. out the three or four million afford the first illustration we have noted of another of the great laws of form evolution, namely, adaptation occurs far more frequently through changes of existing proportions than through numerical addi- It is proportional changes which tion of new characters. separate the swift-moving plesiosaurs (Trinacromerion os- borni), which are invariably provided with long heads, short necks, and broad paddles, from the slow-moving plesiosaurs (Elasmosaurus), which are pro- vided with narrow paddles, short bodies, extremely long necks, and small heads. It is believed that the lizard- like ancestors of the mosasaurs left the land early in Cretaceous time; it is certain that through- years of the Cretaceous epoch they spread into all the oceans of the world, from the conti- nental seas of northern Europe and North America to those of New Zealand. In Europe these animals survived to the very close of Mesozoic time since the type genus of the great AQUATIC REPTILES 209 order Mosasauria (Mosasaurus), taking its name from the River Meuse, was found in the uppermost marine Cretaceous. Detailed knowledge of the structure of these remarkable sea lizards is due chiefly to the researches of Williston and Fic. 87. A Sea Lizarp. Tylosaurus, a giant mosasaur from the inland Cretaceous seas of Kansas, chasing the giant fish Portheus. After a restoration in the American Museum of Natural History, by Charles R. Knight under the author’s direction. Osborn of this country and to those of Dollo in Europe. The head is long and provided with recurved teeth adapted to seiz- ing active fish prey (Fig. 87); the neck is extremely short; as in the plesiosaurs the fore and hind limbs are converted into paddles, symmetrical in proportion; the body is elongate and 210 THE ORIGIN AND EVOLUTION OF LIFE propulsion is not chiefly by means of the fins but by the sinu- ous motions of the body, and especially of the very elongate, broad, fin-like tail. These sea lizards of Upper Cretaceous time (Fig. 76) are analogous or convergent to the sea Croco- dilia (Geosaurus) of Jurassic time and present further analogies with the Triassic ichthyosaur Cymbospondylus and the small Permo-Carboniferous amphibian Cvricotus (Fig. 76). In the American continental seas these animals radiated into the small, relatively slender Clidastes, into the somewhat more broadly finned Platecarpus, and into the giant Tylosaurus, which was capable (Fig. 87) of capturing the great fish of the Cretaceous seas (Portheus). TERRESTRIAL LIFE. CARNIVOROUS DINOSAURS Widely contrasting with these extreme adaptations to aquatic marine life, the climax of terrestrial adaptation in the reptilian skeleton is reached among the dinosaurs, a branch which separated in late Permian or early Triassic time from small quadrupedal, swiftly moving, lizard-like reptiles and before the time of their extinction at the close of the Creta- ceous had evolved into a marvellous abundance and variety of types. In the Upper Triassic of North America, late New- ark time, the main separation of the dinosaurs into two great divisions, (a) those with a crocodile-like pelvis, known as Saurischia, and (b) those with a bird-like pelvis, known as Orni- thischia, had already taken place, and the dinosaurs domi- nated all other terrestrial forms. When Hitchcock in 1836 explored the giant footprints in the ancient mud flats of the Connecticut valley he quite nat- urally attributed many of them to gigantic birds, since at the time the law of parallel mechanical evolution between birds and dinosaurs was not comprehended and the order Dino- CARNIVOROUS DINOSAURS Pm - pee ahd ee @ art reas SS STEGOMUS p' See =. Jon ee eee {ts RHYTIDODON ANCHISAURUS CONNECTICUT TRIASSIC REPTILES Fic. 88. LIFE OF THE CONNECTICUT RIVER VALLEY IN UPPER TRIASSIC (NEWARK) TIME. Anchisaurus, a primitive carnivorous bipedal dinosaur. Rhytidodon, a phytosaur analo- gous but not related to the modern gavials. Stegomus, a small armored phytosaur related to Rhytidodon. Anomepus, a herbivorous bipedal dinosaur related to the “duckbills” or Iguanodonts. Podokesaurus, a light, swift-moving, carnivorous dino- saur of the bird-like type. Restorations (except Rhytidodon) after R. S. Lull of Yale University. Drawn to uniform scale for the author by Richard Deckert. ae PHYLOGENY AND ADAPTIVE RADIATION OF THE DINOSAURS ; MAINLY AFTER LULL. LAST SAUROPODA LAST CARNIVOROUS DINOSAURS LAST BIRD-LIKE DINOSAURS LAST SEATS eer LAST ARMORED DINOSAURS CRETACEOUS A B (¢ 1) f LOWER CRETACEOUS (COMANCHEAN) VARIED- SAUROPODA —— VARIED CARNIVOROUS DINOSAURS BIRD-LIKE DINOSAURS BEAKED DINOSAURS ————————~ ARMORED DINOSAURS ——| PRIMITIVE SAUROPODA FIRST ARMORED DINOSAURS ANCESTRAL SAUROPODA PRIMITIVE CARNIVOROUS DINOSAURS FIRST HORNY-BEAKED DINOSAURS (BIPEDAU) FIRST BIRD-LIKE DINOSAURS FIRST CARNIVOROUS DINOSAURS PERMIAN COMMON STOCK OF DINOSAURS, CROCODILES, BIRDS, PTEROSAURS. ETC. PENNSYLVANIAN R CARBONIFEROUS) FIRST REPTILES Fic. 89. TERRESTRIAL EVOLUTION OF THE DINOSAURS. The ancestral tree of the dinosaurs, originating in Lower Permian time, and branching into five great lines during a period estimated at twelve million years. A, The giant herbivorous Sauropoda which sprang from Lower ‘Triassic carnivorous ancestors. B, Giant carnivorous dinosaurs, which prey upon all the larger herbivorous forms. C, Swift-moving, ostrich-like, carnivorous dinosaurs, related to B. D, Herbivorous Iguanodonts, swift-moving, beaked, or “duck-bill” dinosaurs, related to E. E, Slow- moving, quadrupedal, heavily armored or horned herbivorous dinosaurs, related to D. Prepared for the author by W. K. Gregory, chiefly after Lull. 21.2 THE ORIGIN AND EVOLUTION OF LIFE -sauria was not known. It has since been discovered that many of the ancient dinosaurs, especially those of carnivorous habit, were bird-footed and adapted in structure for rapid, cursorial locomotion; the body was completely raised above Fic. 90. NortH AMERICA IN UPPER Triassic (NEWARK) TIME. The period of the primitive bipedal dinosaurs, with semi-arid, cool to warm climate, and a prevailing flora of cycads and conifers. Remains of amphibians, primitive crocodiles, and dinosaurs are found in the reddish continental deposits. Detail from the globe model in the American Museum by Chester A. Reeds and George Robertson, after Schuchert. the ground, the forward part being balanced with the aid of the long tail. This primitive type of body structure is com- mon to all the dinosaurs, and is evidence that the group underwent a long period of evolution under semi-arid conti- nental conditions in late Permian and early Triassic time. The reptilian group discovered in the Connecticut valley (Fig. CARNIVOROUS DINOSAURS a te. 88) is not inconsistent with the theory of a semi-arid climate advocated by Barrell to explain the reddish continental de- posits not only in the region of the Connecticut valley but over the southwestern Great Plains. The flora of ferns, cycads, and conifers indicates moderate conditions of temperature. Along the Pacific coast there was a great overflow of the seas along the western continental border and an archipelago of volcanic islands. In this region there were numerous coral reefs and an abundance of cephalopod ammonites. In the Fic. 91. A Carnivorous DINOSAUR PREYING UPON A SAUROPOD. Skeletons (left) and restoration (right) of the bipedal dinosaur Allosaurus of Upper Jurassic and Lower Cretaceous time in the act of feeding upon the carcass of A patosaurus, one of the giant herbivorous Sauropoda of the same period. Mounted specimens and restoration by Osborn and Knight in the American Museum of Natural History. interior continental seas great marine reptiles (Cymbospondylus, Fig. 82), related to the ichthyosaurs, were abundant. The primitive light-bodied, long-tailed type of dinosaur of bipedal locomotion originates in this country with Marsh’s Anchisaurus of the Connecticut valley (Fig. 88) and develops into the more powerful form of the Allosaurus of Marsh from the Jurassic flood-plains east of the Rocky Mountains (Fig. gr). Contemporaneous with this powerful animal is the much more delicate Ornitholestes, which is departing from the carnivorous habits of its ancestors and seeking some new form of food. It is in turn ancestral to the remarkable “ostrich dinosaur” of the Upper Cretaceous, Struthiomimus (Ornithomimus), which is bird-like both in the structure of its limbs and feet and in 214 its toothless jaw sheathed in horn. THE ORIGIN AND EVOLUTION OF LIFE In this animal the car- nivorous habit is completely lost; it is secondarily herbivorous. Recently restored skeleton of the light-limbed, bird-like, toothless ‘“ostrich”’ dinosaur, Struth- iomimus (Ornithomimus), after Osborn. oe iereseetosenerats | Lateral view of the “tyrant” dinosaur, Tyran- nosaurus (left), and the ‘ostrich’ dinosaur, Struthiomimus (right), to the same scale. Fic. 92. EXTREMES OF ADAPTATION IN THE “TYRANT” AND THE “OsTRICH” DINOSAURS. Skeletons mounted in the American Museum of Natural History. piece). Its limbs are adapted to very rapid motion. In the meantime the true carnivorous dinosaur line was evolving over the entire northern hemis- phere stage by stage with the evolution of the varied herbivorous group of the dinosaurs. These animals preserved perfect me- chanical unity in the evo- iution of the very swift motions of the hind limb and prehensile powers both of the jaws and of the hind feet, adapted to seizing and rapidly over- coming a_ struggling powerful prey. This series reaches an astounding in the gigantic de- scribed by Osborn from the Upper Cretaceous of Montana (see frontis- climax Tyrannosaurus rex, This “‘king of the tyrant saurians” is in respect to speed, size, power, and ferocity the most destructive life engine which has ever evolved. The excessively small size of the brain, probably weighing less than a pound, which is less CARNIVOROUS DINOSAURS os than 1/4000 of the estimated body weight, indicates that in animals mechanical evolution is quite independent of the evolution of their intelligence; in fact, intelligence compensates for the absence of mechanical perfection. J yrannosaurus is Fic. 93. Four RESTORATIONS OF THE ‘“OstRICH”’ DINosAuR, Struthiomimus (Ornithomimus). A. Showing the mode of progression. B. Illustrating the hypothesis that the animal was an anteater which used the front claws like those of sloths in tearing down anthills. C. Illustrating the hypothesis that it was a browser which supported the fore part of the body by means of the long, curved claws of the fore limb while browsing on trees. D. Illustrating the hypothesis that it was a wading type, feeding upon shrimps and smaller crustaceans. Restorations by Osborn. No satisfactory theory of the habits of this animal has as yet been advanced. an illustration of the law of compensation, first enunciated by Geoffroy St. Hilaire, first, in the disproportion between the diminutive fore imb and the gigantic hind limb, and second, in the fact that the feeble grasping power and consequent degeneration of the fore limb and hand are more than com- pensated for by the development of the tail and the hind claws, 216 THE ORIGIN AND EVOLUTION OF LIFE which enables these animals to feed practically in the same manner as the raptorial birds. | HERBIVOROUS DINOSAURS, SAUROPODA As analyzed by Lull along the lines of modern interpreta- tion, beside the small carnivorous dinosaurs there may be : PLATEOSAURUS REPTILIA_ TRIASSIC Beek, ANCHISAURUS REPTILIA TRIASSIC Fic. 94. ANALOGY BETWEEN THE CARNIVO- Rous Anchisaurus TYPE OF THE TRIASSIC AND THE ANCESTRAL HERBIVOROUS SAURO- pop Typr Plateosaurus. The upper restoration (Plateosaurus) repre- sents a bipedal stage of sauropod evolution which was discovered in the German Trias, in which the transition from carnivorous to herbivorous habits is observed. Recent discovery renders it probable that the herbivorous Sauropoda descend from carniv- orous ancestors like Anchisaurus. Restoration of Plateosaurus modified from Jae- kel. Restoration of Anchisaurus after Lull. traced in the Connecticut Triassic footprints the be- ginnings of an herbivorous offshoot of the primitive carnivorous dinosaur stock, leading into the elephantine types of herbivorous dino- saurs known as the Sauro- poda, which were first brought to our knowledge in this country through the pioneer studies of Marsh and Cope. As there is never any need of haste in the capture of plant life these animals underwent a reversed evo- lution of the limbs from the swift-moving primitive bi- pedal type into a secon- dary slow-moving quadru- pedal ambulatory type. The original power of occa- sionally raising the body on the hind limbs was stil] retained in some of these gigantic forms. The half-way stage between the bipedal and the HERBIVOROUS DINOSAURS Zs, quadrupedal mode of progression is revealed in the recently described Plateosaurus of Jaekel from the Trias of Germany (Fig. 94), an animal which could progress either on two or on four legs. The Sauropoda reached the climax of their evolution dur- ing the close of Jurassic (Morrison formation) and the be- : LOWER /| CRETACEOUS |- PALEQGEOGRAPHY, LOWER CRETACEOUS (UPPER NEOCOMIAN-VELANGIAN-HILS-WEALDEN-TRINITY-MORISSON) TIME AFTER SCHUCHERT, APRIL, 1916 oe s~Y MARINE DEPOSITS eS CONTINENTAL DEPOSITS Oy SIERRA NEVADA Fic. 95. THEORETIC WoRLD ENVIRONMENT IN LOWER CRETACEOUS TIME. The dominant period of the great sauropod dinosaurs. This shows the theoretic South Atlantic continent Gondwana connecting South America and Africa, and the Eurasiatic Mediterranean sea Tethys. Shortly afterward comes the rise of the modern flowering plants and the hardwood forests. The shaded patch over the existing region of Wyo- ming and Colorado is the flood-plain (Morrison) centre of the giant Sauropoda (see Fig. 97). After Schuchert, 1916. ginning of Cretaceous time (Comanchean Epoch). Meanwhile they attained world-wide distribution, migrating throughout a long stretch of the present Rocky Mountain region of North America, into southern Argentina, into the Upper Jurassic of Great Britain, France, and Germany, and into eastern Africa. The last named region is the one most recently explored, and 218 THE ORIGIN. AND EVOLUTION OF LIFE the widely heralded Gigantosaurus (== Brachiosaurus), de- scribed as the largest land-living vertebrate ever found, is RN ne ETT AOL LS TT TTT Fic. 96. NortH AMERICA IN LOWER CRETACEOUS (COMANCHIAN) TIME. This period, also known as the Trinity-Morrison time, is marked by the maximum develop- ment of the giant herbivorous dinosaurs, the Sauropoda. The Sierra Nevada and coast ranges are elevated, also the mountain ranges of the Great Basin which give rise east- ward to the flood-plain deposits (Morrison) in which the remains of the Sauropoda are entombed. ‘This epoch is prior to the birth of the Rocky Mountains, which arose be- tween Cretaceous and Eocene time. Detail from the globe model in the American Museum by Chester A. Reeds and George Robertson, after Schuchert. structurally closely related to and does not exceed in size the sauropods discovered in the Black Hills of South Dakota. Their size is indeed titanic, the length being roo feet, while the HERBIVOROUS DINOSAURS 2109 longest whales do not exceed go feet. In height these sauropods dwarf the straight-tusked elephant of Pleistocene time, which is the largest land product of mammalian evolution. The Sauropoda for the most part inhabited the swampy meadows and flood-plains of Morrison time. They include, besides the DIPLODOCUS - JURA-— CAMARASAURUS JURA- CRETACEOUS REPTILIA CRETACEOUS REPTILIA Fic. 97. THREE PRINCIPAL TYPES OF SAUROPODS. The body form of the three principal types of giant herbivorous Sauropoda which ap- pear to have been almost world-wide in distribution. Camarasaurus, a heavy-bodied, short-limbed quadrupedal type. Dziplodocus, a light- bodied, relatively swift-moving quadrupedal type. Brachiosaurus, a short-bodied quadrupedal type in which the fore limbs are more elevated than the hind limbs. Brachiosaurus attained gigantic size, being related to the recently discovered Giganto- saurus of East Africa. Restorations by Osborn, Matthew, and Deckert. gigantic type Brachiosaurus (~~ Gigantosaurus), with its greatly elevated shoulder and forearm, massive quadrupedal types like Camarasaurus Cope and A patosaurus (— Brontosaurus) Marsh, and the relatively long, slender, swiftly moving Dzflodocus. According to Lull and Depéret the Sauropoda survived until the close of the Cretaceous Epoch in Patagonia and in southern France. In North America they became extinct in Lower Cretaceous time. 220 THE ORIGIN AND EVOLUTION OF LIFE In the final extinction of the herbivorous sauropod type we find an example of the selection Jaw of elimination, attributable Fic. 98. AMPHIBIOUS OR TERRESTRIO-FLUVIATILE THEORY OF THE HABITS OF APATOSAURUS. (Upper.) Apatosaurus (=Brontosaurus), a typical sauropod of Morrison age, quad- rupedal, heavy-limbed, herbivorous, inhabiting the flood-plains (Morrison) and lagoons of the region now elevated into the Rocky Mountain chain of Wyoming and Colorado. (Lower.) Mounted skeleton of A patosaurus (= Brontosaurus) in the American Museum of Natural History. to the fact that these types had reached a cul-de-sac of mechan- ical evolution from which they could not adaptively emerge HERBIVOROUS DINOSAURS OL when they encountered in all parts of the world the new en- vironmental conditions of advancing Cretaceous time. THE IGUANODONTIA Contemporaneous with the culminating period of the evo- lution of the Sauropoda is the world-wide appearance of an Fic. 99. PrrimitivE IGUANODONT Camptosaurus FROM THE UPPER JURASSIC OF WYOMING. This swift bipedal form was contemporary with the giant sauropod A patosaurus and the lighter-bodied Diplodocus. ‘These iguanodonts were defenseless and dependent wholly on alertness and speed, or perhaps on resort to the water, for escape from their enemies. They were the prey of Allosaurus (see Fig. 91). Mounted specimen in the American Museum of Natural History. entirely different stock of bipedal herbivorous dinosaurs in which the pelvis is bird-like (Ornithischia, Seeley). These animals may be traced back (von Huene) to the Triassic Naosaurus. ‘The front of the jaws at an early stage lost the teeth and developed a horny sheath or beak like that of the birds, within which a new bone (predentary) evolves, giving to this order the name Predentata. Entirely defenseless at this stage (Camptosaurus), these relatively small, bipedal types 222 THE ORIGIN AND EVOLUTION OF LIFE Fic. 100. A PAtR OF UPPER CRETACEOUS IGUANO- DONTS FROM MONTANA. After a lapse of 500,000 years of Cretaceous time the Camptosaurus (Fig. 99) evolved into the giant “ duck- billed”? dinosaur Trachodon, described by Leidy and Cope from the Upper Cretaceous of New Jersey and Dakota. Two skeletons of Trachodon annectens (upper) discovered in Montana, as mounted in the American Museum of Natural History, and restoration of the same (lower) by Osborn and Knight. (Compare Fig. 74.) spread all over the northern hemisphere and attained an extra- ordinary adaptive radi- ation in the river- and shore-living ‘‘duck- bill: sdinosaunstst ie iguanodonts of the Cre- taceous Epoch (Fig. 1o1). The adaptive radiation of these ani- mals has only recently been fully determined; it led into three great types of body form, all unarmored. First, the less specialized types which retain more or less the body structure of the earlier Jurassic forms and the famous iguanodont of Bernis- sart, Belgium. Related to these are the krito- saurs of the Cretaceous of Alberta, with a com- paratively narrow head, the protection of which was facilitated by a long, backwardly pro- jecting spine. Second, there are the broadly HERBIVOROUS DINOSAURS B23 duck-billed, wading dinosaurs (Trachodon), with stalking limbs and elevated bodies. Third, there are more fully aquatic, free- swimming forms with crested skulls (Corythosaurus). The ip 4 / Wy, Wy “) Wy Yj ec WAI \ I iS YAM | shia Wy \ : iy | ZN EN AM) tis AAG a Us Lge NN Te Wy! fi : i \ ; / As all pene y, \\i Ti | Ta f Fic. ror. ADAPTIVE RADIATION OF THE IGUANODONT DINOSAURS INTO THREE GROUPS. (Upper.) Three characteristic types: A, Typical “duck-bill” Trachodon; B, Corytho- saurus, the hooded “duck-bill,” with a head like a cassowary, probably aquatic; C, Kritosaurus, the crested “duck-bill”’ dinosaur. Restorations by Brown and Deckert. (Lower.) Mounted skeleton of Corythosaurus in the American Museum of Natural His- tory, recently discovered in the Upper Cretaceous of Alberta, Canada, with the integ- ument impressions and body lines preserved. anatomy and habits of all these forms have been made known recently by American Museum explorations in Alberta, Canada, under Barnum Brown (Fig. tor). The partly armored dinosaurs known as stegosaurs are related to the iguanodonts and belong to the bird-pelvis group 224 THE ORIGIN AND EVOLUTION OF LIFE | (Ornithischia). The small Triassic ancestors of this great group of herbivorous, ornithischian dinosaurs also gave rise to a number of secondarily quadrupedal, slow-moving forms, in which there developed various forms of defensive and offen- sive armature. Of these the Jurassic stegosaurs exhibit a reversed evolution in their locomotion since they pass from a bipedal into a quadrupedal type in which the armature takes Fic. 102. OFFENSIVE AND DEFENSIVE ENERGY COMPLEXES. The carnivorous “tyrant” dinosaur Tyrannosaurus approaching a group of the horned herbivorous dinosaurs known as Ceratopsia. Compare frontispiece. The Ceratopsia are related to the armored Stegosaurus and to the armorless, swift-moving Tguanodontia. Restoration by Osborn in the American Museum of Natural History, painted by Charles R. Knight. the form of sharp dorsal plates and spiny defenses, the exact arrangement of which has been recently worked out by Gil- more. Doubtless when this animal was attacked it drew its head and limbs under its body, like the armadillo or porcu- pine, and relied for protection upon its dorsal armature, aided by rapid lateral motions of the great spines of the tail to ward off its enemies. During the progress of Cretaceous time these stegosaurs became extinct, and by the beginning of the Middle Cretaceous two other herbivorous types are given off from the predentate stock. The first of these are the aggressively and defensively horned Ceratopsia, in which two or three front horns evolved HERBIVOROUS DINOSAURS vO AS step by step, with a great bony frill protecting the neck. This evolution took place stage by stage with the evolution of the predatory mechanism of the carnivorous dinosaurs, so that the climax of ceratopsian defense (Triceratops) was reached simultaneously with the climax of Tyrannosaurus offense. This is an example of the counteracting evolution of offensive and defensive adaptations, analogous to that which we observe to-day in the evolution of the lions, tigers, and leopards, which counteracts with that of the horned cattle and antelopes of Africa, and again in the evolution of the wolves simultaneously with the horned bison and deer in the northern hemisphere. It is a case where the struggle for existence is very severe at every stage of development and where advantageous or dis- advantageous chromatin predispositions in evolution come con- stantly under the operation of the law of selection. ‘Thus in the balance between the reptilian carnivora and herbivora we find a complete protophase of the more recent balance between the mammalian carnivora and herbivora. The climax of defense was reached, however, in another line of Predentata, in the herbivorous dinosaurs, known as Ankylosaurus, in which there developed a close imitation of the armadillo or glyptodon type of mammal, with the head and entire body sheathed in a very dense, bony armature. In these animals not only is motion abandoned as a means of escape, but the teeth become diminutive and feeble, as in most other heavily armored forms of reptiles and mammals. The herbivorous function of the teeth is replaced by the develop- ment of horny beaks. Thus these animals reach a ground- dwelling, slow-moving, heavily armored existence. 220 THE ORIGIN AND EVOLUTION OF LIFE PTEROSAURS There is no doubt that the pterosaurs, flying reptiles, were adapted to fly far out to sea, for their remains are found min- gled with those of the mosasaurs in deposits far from the ancient shore-lines. There is no relation whatever between the feathered birds and these animals, whose analogies in their modes of flight are rather with the bats among the mammals. These flying reptiles are perhaps the most extraor- dinary of all extinct ani- mals. While some ptero- saurs were hardly larger than sparrows, others sur- passed all living birds in the spread of the wings, FIG. 103. RESTORATION OF THE PTERODACTYL, although inferior to many SHOWING THE SOARING FLIGHT. birds in the bulk of the After the Aéronautical Journal, London. Be dy. Tio betieredatiee they depended almost entirely upon soaring for progression. The head in the largest types of the family (Pteranodon) is converted into a great vertical fin, used, no doubt, in directing flight, with a long, backwardly projecting bony crest which served in the balancing of the elongate and compressed bill. The feeble development of the muscles of flight in these an- cient forms is compensated for by the extreme lightness of the body and the hollowness of the bones. ORIGIN OF BIRDS It is believed that in late Permian or early Triassic time a small lizard-like reptile of partly bipedal habit and remotely related to the bipedal ancestors of the dinosaurs passed from ORIGIN OF BIRDS 20 85| a terrestrial into a terrestrio-arboreal mode of life, probably for purposes of safety. This early arboreo-terrestrial phase is indicated in the most ancient known birds (Archeopteryx) by the presence of claws at the ends of the bones of the wing, fit- ting them for clinging to trees, it is argued, through analogy to the tree-clinging habits of existing young hoatzins of South TERTIARY FLIGHTLESS RUNNING BIRDS MODERNIZED BIRDS UPPER CRETACEOUS TOOTHED DIVERS PRIMITIVE TOOTHED BIRDS 2 FIRST RADIATION FROM ARBOREAL INTO TERRESTRIAL AND AQUATIC BIRDS LOWER CRETACEOUS ({COMANCHEAN) JURASSIC TRIASSIC 7 FIRST BIRDS-BIPEDAL, CURSORIAL. CLIMBING (HIGH BODY TEMP., RELATIVELY HIGH = BRAIN) PERMIAN 5 COMMON ANCESTORS OF CROCODILES, PHYTOSAURS, ___ DINOSAURS, PTEROSAURS AND BIRDS PENNSYLVANIAN ER CARBONIFEROUS) MISSISSIPPIAN Rg CARBONIFEROUS ORIGIN AND ADAPTIVE RADIATION OF THEBIRDS W. K. GREGORY. 1916 Fic. 104. ANCESTRAL TREE OF THE BIRDS. The ancestors of the birds branch off in Permian time from the same stock that gives rise to the dinosaurs, adding to swift, bipedal locomotion along the ground the power of tree climbing and, with their very active life, the development of a high and uniform body temperature. Primitive types of birds exhibit a fore limb terminating in claws, probably for grasping tree branches. The power of flight began to develop in Triassic time through the conversion of scales into feathers either on the fore limbs (two-wing theory) or on both fore and hind limbs (four-wing theory). From the Jurassic birds (Archeopteryx), capable of only feeble flight, there arises an adaptive radiation into aérial, arboreal, arboreo-terrestrial, terrestrial, and aquatic forms, the last exhibiting a reversal of evolution. Diagram prepared for the author by W. K. Gregory. America. Ancestral tree existence is rendered still more prob- able by the fact that the origin of flight was apparently sub- served in the parachute function of the fore limb and perhaps of both the fore and hind limbs for descent from the branches of trees to the ground. Two theories have been advanced as to the origin of flight in the stages succeeding the arboreal phase of bird evolution. First, the pair-wing theory, developed from the earlier studies on Archaeopteryx, in which the transformation of lateral scales 228 THE ORIGIN AND EVOLUTION OF LIFE into long primary feathers on the fore limbs and at the sides of the extended tail would afford a glissant parachute support for short flights from trees to the ground (Fig. 106). Quite Fn 3 recently a four-wing theory, the ate parr oe ue laoblers® tetrapteryx theory, has been pro- PIGEON (right). posed by Beebe, based on the Showing the abbreviation of the tail into observation of the presence of the pygostyle and the conversion of the grasping fore limb into the bones great feathers on the thighs of of the wing. After Heilman. embryos of modern birds and of supposed traces of similar feathers on the thighs of the old- est known fossil bird, the Ar- , cheopteryx of Jurassic age. Ac- cording to this hypothesis after the four-wing stage was reached the two hind-leg wings degen- erated as the flight function evolved in the spreading feathers of the forearm-wings and the rudder function was perfected Fic. 106. SILHOUETTES OF Archeop- in the spreading feathers of the teryx (A) AND PHEASANT (B). tail (Fi 107) Both of these Based on the two-wing theory. After 8° Heilman. uy (( ee ee i ie a aa" ye ys? ay __—, oa Mey ae “, “ey ° “C¢ >> fis aah " " iN i (Giese eo ( Fic. 107. Four EVOLUTIONARY STAGES IN THE HYPOTHETICAL FOUR-WINGED BIRD. After Beebe. S Uy aa LLL LAA S ORIGIN OF BIRDS 229 hypotheses assign two phases to the origin of flight in birds: first, a primary terrestrial phase, during which the peculiar characters of the hind limbs and feet were developed with their strong analogies to the bipedal feet of dinosaurs; second, a purely arboreal phase. It is believed by the adherents of both the two- Fic. 109. RESTORATION OF THE ANCIENT Jurassic Birp, Archeopteryx. Capable of relatively feeble flight. After Heilman. Fic. 108. THEORETIC MopE oF PARA- CHUTE FLIGHT OF THE PRIMITIVE Brirp. Based on the four-wing theory. After Beebe. wing and the four-wing theory that following the arboreal phase, in which the powers of flight were fully developed, there occurred among the struthious birds, such as the ostriches, a secondary terres- trial phase in which the powers of flight were secon- darily lost and rapid cursorial locomotion on the ground was secondarily developed. This interpretation of the foot and limb structure associated with the loss of teeth, which is characteristic of all the higher birds, will explain the close analogies which exist between the ostrich-like dinosaur Stru- ZO THE ORIGIN AND EVOLUTION OF LIFE thiomimus and the modern cursorial flightless forms of birds, such as the ostriches, rheas, and cassowaries. In the opposite extreme to these purely terrestrial forms, the flying arboreal birds also gave off the water-living birds, one phase in the evolution of which is represented in the loon- like Hesperornis, the companion of the pterosaurs and mosa- saurs in the Upper Cretaceous seas. It was on the jaws of the Fic. 110. REVERSED AQUATIC EVOLUTION OF WING AND Bopy Form. Wing of a penguin (A) transformed into a fin externally resembling the fin of a shark (B). Skeleton of Hesperornis (C) in the American Museum of Natural History and restora- tion of Hesperornis (D) by Heilman, both showing the transformation of the flying bird into a swimming, aquatic type, and its convergent evolution toward the body shape of the shark, ichthyosaur, and dolphin (compare Fig. 41). Hesperornis and smaller [chthyornis that Marsh made his sen- sational announcement of the discovery of birds with teeth, a discovery confirmed by his renewed studies of the classic fossil bird type, the Jurassic Archeopteryx. These divers of the Cretaceous seas (Hesperornis) are analogous to the modern loons, and represent one of the many instances in which the tempting food of the aquatic habitat has been sought by ani- mals venturing out from the shore-lines. As in the most highly specialized modern swimming birds, the Antarctic penguins, the wing secondarily evolves into a fin or paddle, while the ARRESTED REPTILIAN EVOLUTION 230 body secondarily develops a fusiform shape in order to dimin- ish resistance to the water in rapid swimming. POSSIBLE CAUSES OF THE ARRESTED EVOLUTION OF THE REPTILES Of the eighteen great orders of reptiles which evolved on land, in the sea, and in the air during the long Reptilian Era of 12,000,000 years, only five orders survive to-day, namely, the turtles (Testudinata), tuateras (Rhynchocephalia), lizards (Lacertilia), snakes (Ophidia), and crocodiles (Crocodilia). The evolution of the members of these five surviving or- ders has either been extremely slow or entirely arrested during the 3,000,000 years which are generally assigned to Tertiary time; we can distinguish only by relatively minor changes the turtles and crocodiles of the base of the Tertiary from those living to-day. In other words, during this period of 3,000,000 years the entire plant world, the invertebrate world, the fish, the amphibian, and the reptilian worlds have all remained as relatively balanced, static, unchanged or persistent types, while the mammals, radiating 3,000,000 years ago from very small and inconspicuous forms, have undergone a phenomenal evolution, spreading into every geographic region formerly occupied by the Reptilia and passing through multitudinously varied phases not only of direct but of alternating and of reversed evolution. During the same epoch the warm-blooded birds were doubtless evolving, although there are relatively few fossil records of this bird evolution. This is a most striking instance of the differences in chroma- tin potentiality or the internal evolutionary impulses under- lying all visible changes of function and of form. If we apply our law of the actions, reactions, and interactions of the four physicochemical energies (p. 21), there are four reasons why 232 THE ORIGIN AND EVOLUTION OF LIFE we may not attribute this relatively arrested development of the reptiles either to an arrested physicochemical environment, to an arrested life environment, or to the relative bodily iner- tia of reptiles which affects the body-protoplasm and body- chromatin. ‘These four reasons appear to be as follows: First: We have noted that among the reptiles the velocity of purely mechanical adaptation is quite independent both of brain power and of nervous activity, a fact which seems to strike a blow at the psychic-direction hypothesis (p. 143), on which the explanations of evolution by Lamarck, Spencer, and Cope so largely depend. The law that perfection of mechan- ical adaptation is quite independent of brain power also holds true among the mammals, because the small-brained mammals of early Tertiary time, the first mammals to appear, evolve as mechanisms quite as rapidly or more rapidly than the large- brained mammals. Second: The law of rapidity of character evolution is inde- pendent also of body temperature, for, while the mechanical evolution of the warm-blooded birds and mammals is very rapid and very remarkable it can hardly be said to have ex- ceeded that of the cold-blooded reptiles. Thus the causes of the velocity of character evolution in mechanism need not be sought in the psychic influence of the brain, in the nervous system, in the “Lamarckian”’ influence of the constant exer- cise of the body, nor in a higher or lower temperature of the circulatory system. Third: Nor has the relatively arrested evolution of the Reptilia during the period of the Age of Mammals been due to arrested environmental conditions, for during this time the environment underwent a change as great as or greater than that during the preceding Age of Reptiles. Fourth, and finally, there is no evidence that natural selec- ARRESTED REPTILIAN EVOLUTION 233 tion has exerted less influence on reptilian evolution during the Age of Mammals than previously. Thus we shut out four out of five factors, namely, physical environment, individual habit and development, life environment, and selection as reasonable causes of the relative arrest of evolution among the reptiles. Consequently the causes of the arrest of evolution among the Reptilia appear to lie in the internal heredity-chromatin, z. e., to be due to a slowing down of physicochemical inter- actions, to a reduced activity of the chemical messengers which theoretically are among the causes of rapid evolution. The inertia witnessed in the entire body form of static or per- sistent types is also found to occur in certain single characters of the individual. Recurring to the view that evolution is in part the sum of the acceleration, balance, or retardation of the velocity of single characters, the five surviving orders of the reptiles appear to represent organisms in which the greater number of characters lost their velocity at the close of the Age of Reptiles, and consequently the order as a whole re- mained relatively static. CHAPTER VIII EVOLUTION OF THE MAMMALS First mammals, of insectivorous and tree-living habits. Single character evolution, physicochemical interaction, coordination, and complexity. Problem as to the causes of the origin of new characters and of new bodily proportions. Adaptations of the teeth and of the limbs as observed in direct, reversed, alternate, and counteracting evolution. Physiographic and climatic environment during the period of mammalian evolution, in a measure deduced from adaptive variations in teeth and feet of mammals. Conclusions, present knowledge of biologic evolution among the verte- brate animals. Future lines of inquiry into the causes of evolution. Ir required a man of genius like Linneus to conceive the inclusion within the single class Mammalia of such diverse Fic. 111. THE SEI WHALE, BALZNOPTERA BOREALIS, Which attains a total length of forty-nine feet. Restoration (upper) and photograph (lower) after Andrews. forms as the tiny insect-loving shrew and the gigantic preda- ceous whale. It has required one hundred and twenty-five years of continuous exploration and research to establish the fact that the whale type (Fig. 111), is not only akin to but 234 ORIGIN OF MAMMALS 235 is probably a remote descendant of an insectivorous type not very distant from the alsin tree shrews (Fig. 112), the @ transformation of size, of func- tion, and of form between these two extremes having taken place within a period broadly estimated in our geologic time scale at about 10,000,000 years. Fic. 112. THE TREE SHREW Tupaia. Insectivore, considered to be near the pro- totype form of all the higher placental mammals. ORIGIN OF THE Mammats, INSEc- TIVOROUS, ARBOREAL To the descent of the mammals Huxley was the first, in essaying the reconstruction of the great ancestral tree, to apply Darwin’s principles on a large scale and to prophesy that the very remote ancestral form of all the mammals was of an Fic. 113. Primitive Types oF MONOTREME AND MARSUPIAL. insectivore type. Subsequent re- ; (Below.) Monotreme type—Echid- search! has all tended in the same na, the spiny ant-eater. (Above.) Marsupial type—Didel- phys, the arboreal opossum of habits and in many ways to arboreal — South =America. After photo- graphs of specimens in the New modes of existence as characteristic York Zoological Park. direction, pointing to insectivorous 1 This insectivorous and tree-inhabiting theory of mammalian origin has recently been advocated by Doctor William Diller Matthew of the American Museum of Natural History, by Doctor William K. Gregory of Columbia University (‘‘The Orders of Mam- mals”), and Doctor Elliot Smith of the University of Glasgow. 236 THE ORIGIN AND EVOLUTION OF LIFE of the earliest mammals. Proofs of arboreal habit are seen in the limb-grasping adaptations of the hind foot in many prim- itive mammals, and even in the human infant. Thus the ORIGIN AND ADAPTIVE RADIATION OF THE MAMMALS W. K. GREGORY, 1916" | necor | S$ RI Boor =e MANATEES RODENTS EDENTATES OPOSSUMS A RUSTE ALIAN EGG-LAYING JAMMAL! ARSUPIALS MAMMALS CENOZOIC QUATER- v z i 9 g m 8 aoe = ——_ [casa ol Reamaaste TERTIARY oo c Q Q o nm Zz m pu eal A af hal IRST ARSUPI ‘a ANATEES ARIED FI IN T sBAT: Gant VORES RaGUA Fine FIRST. gS ENTATES SS 1 Y : FIRS’ PALEOCENE ARwoRES | \PRIMITIV E Seenclitcres IED Al Ic PLA q UPPER CRETACEOUS lg ie ne ne ie RST ERENT ee oe MAMMALS, LOWER , CRETACEOUS ({COMANCHEAN) fe ITUBERCULATES [ee x yee ae MESOZOIC JURASSIC TRIASSIC PERMIAN CARBONIFEROUS PALAEOZOIC Fic. 114. ANCESTRAL TREE OF THE MAMMALS. Adaptive radiation of the Mammalia, originating from Triassic cynodont reptiles and dividing into three main branches: (A) the primitive, egg-laying, reptile-like mammals (Monotremes); (B) the intermediate pouched, viviparous mammals (Marsupials— opossums, etc.); and (C) the true Placentals which branch off from small, primitive, arboreo-insectivorous forms (Trituberculata) of late Triassic time into the four grand divisions (1) the clawed mammals, (2) the Primates, (3) the hoofed mammals, and (4) the cetaceans. Dividing into some thirty orders, this grand evolution and adaptive radiation takes place chiefly during the four million years of Upper Cretaceous and Tertiary time. As among the Reptilia, the primary arboreo-terrestrial adaptive phases radiate by direct evolution into all the habitat zones, and by reversed and alternate evolu- tion develop backward and forward in adaptation to one or another habitat zone. Dia- gram prepared for the author by W. K. Gregory. existing tree shrews, the tupaias of Africa (Fig. 112), in many characters resemble the hypothetic ancestral forms of Creta- ceous time from which the primates (monkeys, apes, and man) may have radiated. ORIGIN OF MAMMALS 237 Following Cuvier, Owen, and Huxley in Europe, a period of active research in this country began with Leidy in the middle of the nineteenth century and was continued in the arid regions of the West by Cope, Marsh, and their succes- sors with such energy that America has become the chief cen- tre of vertebrate paleontology. When we connect this research with the older and the more recent explorations by men of all countries in Europe, Asia, Africa, Australia, and South Amer- ica, we are enabled to reconstruct the great tree of mammalian descent (Fig. 114) with far greater fulness and accuracy than that of the reptiles, amphibians, or fishes (Pisces). The connection of the ancestral mammals with a reptilian type of Permian time is theoretically established through the survival of a single branch of primitive egg-laying mammals (Monotremata, Fig. 113) in Australia and New Guinea; while the whole intermediate division, consisting of the pouched mammals (Marsupialia) of Australia, which bring forth their young in a very immature condition, represents on the great continent of Australia an adaptive radiation which also sprang from a small, primitive, tree-living 1. Whales. type of mammal, typified by the ex- 2. Seals (marine carnivores). isting opossums of North and South 3: pea Ore® oreo ial)- é ; : 4. Insectivores. America (Fig. 113). The third great < Bats. group (Placentalia) includes the ©. Primates: mammals in which the unborn way ; , Monkeys, young are retained a longer period Apes, within the mother and are nourished = vee through the circulation of nutrition is Terie te in the placenta. g. Rodents. o. Edentates. The adaptive radiation of the ten *° great branches of the placental stock from the primitive insec- tivorous arboreal ancestors produced a mammalian fauna which 238 THE ORIGIN AND EVOLUTION OF LIFE inhabited the entire globe until the comparatively recent period of extermination by man, who through the invention of tools in Middle Pleistocene time, about 125,000 years ago, became the destroyer of creation. SINGLE CHARACTER EVOLUTION AND PHYSICOCHEMICAL CORRELATION The principal modes of evolution as we observe them among the mammals are threefold, namely: I. The modes in which new characters first appear, whether suddenly or gradually and continuously, whether accidentally or according to some law. II. The modes in which characters change in proportion, quantitatively or intensively, both as to form and color. III. The modes in which all the characters of an organism respond to a change of environment and of individual habit. The key to the understanding of these three modes is to be sought first in changes of food and in changes of the medium in which the mammals move, whether on the earth, in the water, or in the air. The complexity of the environmental influence becomes like that of a lock with an unlimited number of combinations, because the adaptations of the teeth to varied forms of insectivorous, carnivorous, and herbivorous diet may be similar among mammals living in widely different habitat zones, while the adaptations of the locomotor apparatus, the limbs and feet, to the primary arboreal zone may radiate into structures suited to any one of the remaining ten life zones. Thus there is invariably a double adaptive and inde- pendent radiation of the teeth to food and of the limbs to pro- gression, and therefore two series of organs are evolving. For example, there always arises a more or less close analogy be- tween the teeth of all insect-eating mammals, irrespective of CHARACTER EVOLUTION 230 the habitat in which they find their food. Similarly there arises a more or less close analogy between the motor organs of all the mammals living in any particular habitat; thus the glis- sant or volplaning limbs of all aéro-arboreal types are exter- nally similar, irrespective of the ancestral orders from which HABITAT CHANGE ACCOMPANYING CHANGE OF FUNCTION BATS PTEROSAURS “FLYING" PHALANGERS GALEOPITHECUS FLYING" LIZARD “FLYING” SQUIRRELS (LEAPING OR PHALANGERS, LEMURS CLIMBING IN SQUIRRELS TREES) CHAMAELEONS (TRANSITIONAL MACAQUES TO TERRESTRIAL) GORILLA (WALKING MANY INSECT!IVORES RUNNING BABOONS, MANY RUNNING TYPES JUMPING) JUMPING RODENTS KANGAROOS (TRANSITIONAL TO DIGGING i ee eer MANY CLAWED MAMMALS MANY REPTILES TORTOISES (DIGGING) MOLES, POUCHED MOLES SHREWS, YAPOK, BEAVER (TRANSITIONAL, CAPYBARA, HIPPOPOTAMUS, MANY LIZARDS PARTIALLY AQUATIC) POLAR BEARS, OTTERS MANY TURTLES CROCODILES (LIVING IN FRESH WATER) POND TURTLES LITTORAL “MING ALONG SHORE MANATEE MANY EXTINGT. REPT REPTILES OR IN ESTUARIES) SEALS WALRUS F SEA TURTLE! PELAGIC ““harines eet (LIVING AT GREAT DEPTHS FIN-BACK WHALES SOME MOSASAURS OR DIVING TO GREAT DEPTHS) MOTOR ADAPTATIONS OF DIFFERENT ANIMALS TO SIMILAR LIFE ZONES Fic. 115. ADAPTIVE RADIATION OF THE MAMMALS. The mammals, probably originating in arboreal leaping or climbing phases, radiate adaptively into all the other habitat zones and thus acquire many types of body form and of locomotion more or less convergent and analogous to those previously evolved among the reptiles (shown in the right-hand column), the amphibians, and the fishes. Diagram by Osborn and Gregory. they are derived. A mammal may seek any one of twelve different habitat zones in search of the same general kind of food; conversely, a mammal living in a single habitat zone may seek within it six entirely different kinds of food. This principle of the independent adaptation of each organ of the body to its own particular function is in keeping with the heredity law of individual and separate evolution of “‘char- acters’? and ‘‘character complexes” (p. 147), and is fatal to 240 THE ORIGIN AND EVOLUTION OF LIFE some of the hypotheses regarding animal structure and evolu- tion which have been entertained since the first analyses of - animal form were made by Cuvier at the beginning of the last century. ‘The independent adaptation of each character group to its own particular function proves that there is no such essen- tial correlation between the structure of the teeth and the struc- ture of the feet as Cuvier claimed in what was perhaps his most famous generalization, namely, his ‘‘ Law of Correlation.’’! Again this principle, of twofold, threefold, or manifold adap- tation, is fatal to any form of belief in an internal perfecting tendency which may drive animal evolution in any particular direction or directions. Finally, it is fatal to Darwin’s original natural-selection hypothesis, which would imply that the teeth, limbs, and feet are varying fortuitously rather than evolving under certain definite although still unknown laws. The adaptations which arise in the search of many varieties of food and in overcoming the mechanical problems of loco- motion, offense, and defense in the twelve different habitat zones are not fortuitous. On the contrary, observations on successive members of families of mammals in process either of direct, of reversed, or of alternate adaptation admit of but one interpretation, namely, that the evolution of characters is in definite directions toward adaptive ends; nor is this definite direction limited by the ancestral constitution of the heredity- chromatin as conceived in the logical mind of Huxley. The passage in which Huxley expressed this conception is as follows: “The importance of natural selection will not be impaired even if further inquiries should prove that variability is definite, and is determined in certain directions rather than in others, by 1 Cuvier’s law of correlation has been restated by Osborn. There is a fundamental correlation, coordination, and cooperation of all parts of the organism, but not of the kind conceived by Cuvier, who was at heart a special creationist. | Contrary to Cuvier’s claim, it is impossible to predict from the structure of the teeth what the structure of the feet may prove to be. CHARACTER EVOLUTION 241 conditions inherent in that which varies. It is quite conceiv- able that every species tends to produce varieties of a limited number and kind, and that the effect of natural selection is to favor the development of some of these, while it opposes the development of others along their predetermined lines of 1 Tt is true that the variations of the organ- modification. ism are in some respects limited in the heredity-chromatin, as Huxley imagined; on the contrary, every part of a mammal may exhibit such plasticity in course of geologic time as enables it to pass from one habitat zone into another, and from that into still others until finally traces of the adaptations to pre- vious habitats and anatomical phases may be almost if not entirely lost. The heredity-chromatin never determines be- forehand into what new environment the lot of a mammal family may be cast; this is determined by cosmic and plane- tary changes as well as by the appetites and initiative of the organism (p. 114). For example, one of the most remarkable instances which have been discovered is that of the reversed aquatic adaptation of Zeuglodon,’ first terrestrial, then aquatic, in succession a dog-like, a fish-like, and finally an eel-like mammal. These peculiar whales (Archeoceti) appear to have originated in the littoral and pelagic waters of Africa in Eocene time from a purely terrestrial ancestral form of mammal (allied to Hyenodon), in which the body is proportioned like that of the wolf or dog, and this terrestrial mammal in turn was descended from a very remote arboreal ancestor. ‘Thus in its long history the Zeuglodon passed through at least three habitat zones and as many life phases. Yet in another sense Huxley was right, for palzontolo- 1 Huxley, Thomas, 1893, p. 223 (first published in 1878). * Zeuglodon itself is a highly specialized side branch of the primitive toothed whales. The true whales may have arisen from the genera Protocetus, probably ancestral to the toothed whales, and Patriocetus which combines characters of the zeuglodonts and whalebone whales. 242 THE ORIGIN AND EVOLUTION OF LIFE gists actually observe in the characters springing from the heredity-chromatin a predetermination of another kind, namely, the origin through causes we do not understand of a tendency toward the independent appearance or birth at different periods of geologic time of szmilar new and useful characters. In fact, a very large number of characters spring not from the visible ancestral body forms but from invisible predispositions and tendencies in the ancestral heredity-chromatin. For example, all the radiating descendants of a group of hornless mammals may at different periods of geologic time give rise to similar horny outgrowths upon the forehead. This heredity principle partly underlies what Osborn has termed the law of rectigra- dation. Moreover, once a new character or group of characters makes its visible appearance in the body its invisible chromatin evolution may assume certain definite directions and become cumulative in successive generations in accordance with the principle of Mutationsrichtung, first perceived by Neumayr (p. 138); in other words, the tendency of a character to evolve in one direction often accumulates in successive generations until it reaches an extreme. - The application of our law of quadruple causes, namely, of the incessant action, reaction, and interaction of the four physicochemical complexes under the influence of natural selection, to the definite and orderly origin of myriads of char- acters such as are involved in the transformation of a shrew type of mammal into the quadrupedal wolf type and of the wolf type into the Zeuglodon eel type, has not yet even ap- proached the dignity of a working hypothesis, much less of an explanation. The truth is that the causes of the orderly co- adaptation of separable and independent characters still remain a mystery which we are only beginning to dimly penetrate. As another illustration of the complexity of the evolution CHARACTER EVOLUTION 243 process in mammals, let us observe the operation of Dollo’s law of alternate adaptation (p. 202) in the evolution of the tree kangaroo (Dendrolagus), belonging to the marsupial or pouched division of the Mammalia. This is a case where many of the intermediate stages are known to survive in existing types. These tree kangaroos theoretically have passed through four phases, as follows: (1) An arboreo-terrestrial phase, including primitive marsupials like the opossum, with no special adap- TREE KANGAROOS WITH FEET OF LEAPING TYPE, BUT READAPTED FOR CLIMBING lee ee ee ee ee ee es ee ee ee — eae a ARBORS TERRE | Surin seecint anaPranions FOR CLIMBING KANGAROOS, WITH FEET OF LEAPING TYPE TERRESTRIAL | FOURTH TOE MUCH ENLARGED Fic. 116. Four PHASES OF ALTERNATING ADAPTATION IN THE KANGAROO MARSUPIALS, ACCORDING TO DOoLLo’s LAw. . Primitive arboreo-terrestrial phase—tree and ground living forms. . Primitive arboreal phalanger phase—tree-living forms. . Kangaroos—terrestrial, saltatorial phase—ground-living, jumping forms. . Tree kangaroos—secondarily arboreal, climbing phase. bh OD H tations for climbing; (2) a true arboreal phase of primitive tree phalangers with the feet specialized for climbing purposes through the opposability of the great toe (hallux), the fourth toe enlarged; (3) a cursorial terrestrial phase, typified by the kangaroos, with feet of the leaping type, the big toe (hallux) reduced or absent, the fourth toe greatly enlarged; (4) a second arboreal phase, typified by the tree kangaroos (Dendrolagus), with limbs fundamentally of the cursorial terrestrial leaping type but superficially readapted for climbing purposes. It is clear that there can be no internal perfecting tendency or predetermination of the heredity-chromatin to anticipate such a tortuous course of evolution from terrestrial into arbo- real life, from arboreal back to a highly specialized terrestrial 244 THE ORIGIN AND EVOLUTION OF LIFE life, and finally from the leaping over the ground of the kan- garoo into the incipiently specialized arboreal phase of the tree kangaroo. In the evolution of the tree kangaroos adap- tation is certainly not limited by the inherent tendencies of the heredity-chromatin to evolve in certain directions. The physicochemical theory of these remarkable alternate adap- tations is that an animal leaving the terrestrial habitat and taking on arboreal habits initiates an entirely new series of actions, reactions, and interactions with its physical environ- ment, with its life environment, in its body cell and individual development, and, in some manner entirely unknown to us, in its heredity-chromatin, which begins to show new or modified determiners of bodily character. That natural selection is continuously operating at every stage of the transformation there can be no doubt. One interpretation which has been offered up to the pres- ent time of the mode of transformation of a terrestrial into an arboreal mammal is through a form of Darwinism known as the ‘“‘organic selection”? or “coincident selection” hypothesis, which was independently proposed by Osborn,! Baldwin, and Lloyd Morgan, namely: that the individual bodily modifications and adaptations caused by growth and habit (while not them- selves heritable) would tend to preserve the organism during the long transition into arboreal life; they would tend to nurse the family over the critical period and allow time to favor all pre- dispositions and tendencies in the heredity-chromatin toward arboreal function and structure, and would tend also to elim- inate all structural and functional predispositions in the hered- ity-chromatin which would naturally adapt a mammal to life in any one of the other habitat zones. This interpretation is consistent with our law that selection is constantly operating 1 Osborn, H. F., 1897. CAUSES OF EVOLUTION 245 on all the actions, reactions, and interactions of the body, but it does not help to explain the definite origin of new characters ¢ which cannot enter into “organic selection” before they exist. Nor is there any evidence that while adapting itself to one mode of life fortuitous variations in the heredity-chromatin for every other mode of life are occurring. THEORETIC CAUSES OF EVOLUTION IN MAMMALS We have thus far described only the modes of evolution and said nothing of the causes. In speculating on the causes of character evolution in the mammals, in comparison with similar body forms and characters in the lower vertebrates and even in the invertebrates, it is very important to keep in mind the preceding evidence that mammalian heredity-chromatin may preserve all the useful functional and structural properties of action, reaction, and interaction which have accumulated in the long series of ancestral life forms from the protozoan and even the bacterial stage. Since structurally the mammalian embryo passes through primitive protozoan (single-celled) and metazoan (many-celled) phases, it is probable that chemically it passes through the same. The heredity-chromatin even in the. development of the highest mammals still recalls primitive stages in the devel- opment of the fishes, for example, the gill-arch structure at the side of the throat, which through change of function serves to form the primary cartilaginous jaws (Meckelian cartilages) of mammals as well as the bony ossicles which are connected with the auditory function of the middle ear (Reichert’s theory). Similarly profound structural ancestral phases in protozoan, fish, and reptile structure pervade every part of the mammalian body. In race evolution there may be changes of adaptation as in the law of change of function (Prinzip des Funk- 249 THE ORIGIN AND EVOLUTION OF LIFE tionswechsels), first clearly enunciated by Anton Dohrn in 1875. But no function is lost without good cause, and the heredity- chromatin retains every character which through change of function and adaptation can be made useful. The same law which we observe in the conservation of all adaptive characters and functions will probably be discovered also in the conservation of ancestral physicochemical actions, reactions, and interactions of the organism from the protozoan stages onward. The primordial chemical messengers—enzymes or organic catalyzers, hormones and chalones, and other accele- rators, retarders, and balancers of organ formation (see p. 72)— are certainly not lost; if useful, they are retained, built up, and unceasingly complicated to control the marvellous coordina- tions and correlations of the various organs of the mammalian body. The principal endocrine (internal secretory) as well as duct secretory glands established in the fish stage of evolution (p. 160), through which they can be partly traced back even to the lancelet stage (chordate), doubtless had their beginnings among the ancestors (protochordates) of the vertebrated animals, which extend back into Cambrian and pre-Cambrian time. Since these chemical messenger functions among the mammals are enormously ancient, we may attribute an equal antiquity to the powers of chemical storage and entertain the idea that the chromatin potentiality of storing phosphate and carbonate of lime for skeletal and defensive armature in the protozoan stage of 50,000,000 years’ antiquity is the same chromatin potentiality which builds up the superb internal skeletal struc- tures of the Mammalia and the highly varied forms of offen- sive and defensive armature either of the calcium compound or the chitinous type. It is, moreover, through the fundamental similarity of the physicochemical constitution of the fishes, amphibians, reptiles, CAUSES OF EVOLUTION 247 birds, and mammals that we may interpret the similarities of form evolution and understand why, the other three causes being similar, mammals repeat so many of the habitat form phases in adaptation to the environments previously passed through by the lower orders of life. Thus advancing struc- tural complexity is the reflection or the mirror of the invisible physicochemical complexity; the visible structural complexity of a great animal like the whale (Fig. 234), for example, is something we can grasp through its anatomy; the physico- chemical complexity of the whale is quite inconceivable. In research relating to the physicochemical complexity of the mammals, so notably stimulated by the work of Ehrlich and further advanced by later investigators, there are perhaps few studies more illuminating than those of Reichert and Brown! on the crystals of oxyhemoglobin, the red coloring matter of the mammalian blood. Their research proves that every species of mammal has its highly distinctive specific and generic form of hemoglobin crystals, that various degrees of kinship and specific affinity are indicated in the crystallog- raphy of the hemoglobin. For example, varieties of the dog family, such as the domestic dog, the wolf, the Australian dingo, the red, Arctic, and gray fox, are all distinguished by only slightly differing crystalline forms of oxyhemoglobin. The authors’ philosophic conclusions arising from this research are as follows:! | “The possibilities of an inconceivable number of constitu- tional differences in any given protein are instanced in the fact that the serum-albumin molecule may, as has been estimated, have aS many aS 1,000,000,000 stereoisomers. If we assume that serum-globulin, myoalbumin, and other of the highest pro- 1 Reichert, E. T., and Brown, A. P., 1909, pp. iii-iv. 1 Certain insertions in brackets being made for purposes of comparison with other portions of this series of lectures. 248 THE ORIGIN AND EVOLUTION OF LIFE teins may have a similar number, and that the simpler proteins and the fats and carbohydrates and perhaps other complex organic substances, may each have only a fraction of this number, it can readily be conceived how, primarily by differ- ences in chemical constitution of vital substances, and secon- Fic. 117. EVOLUTION OF PROPORTION. ADAPTATION IN LENGTH OF NECK. Short-necked okapi (left), the forest-living giraffe of the Congo, which browses upon the lower branches of trees. Long-necked giraffe (right), the plains-living type of the African savannas, which browses on the higher branches of trees. After Lang. darily by differences in chemical composition, there might be brought about all of those differences which serve to charac- terize genera, species, and individuals. Furthermore, since the factors which give rise to constitutional changes in one vital substance would probably operate at the same time to cause related changes in certain others, the alterations in one may logically be assumed to serve as a common index to all. “In accordance with the foregoing statement it can readily be understood how environment, for instance, might so affect CAUSES OF EVOLUTION 249 the individual’s metabolic processes as to give rise to modifica- tions of the constitutions of certain corresponding proteins and other vital molecules which, even though they be of too subtle a character for the chemist to detect by his present methods, may nevertheless be sufficient to cause not only physiological and morphological differentiations in the individual, but also r / Fic. 118. SHORT-FINGEREDNESS (BRACHYDACTYLY) AND LONG-FINGEREDNESS (DOLICHO- DACTYLY). CONGENITAL, AND DUE TO INTERNAL SECRETION. (Left.) Congenital brachydactyly, theoretically due either to a sudden alteration in the chromatin or to a congenital defect in the pituitary gland. After Drinkwater. (Centre.) Brachydactyly, after birth, due to abnormally excessive secretions of the pituitary gland. After Cushing. (Right.) Dolichodactyly, after birth, due to abnormally insufficient secretions of the pituitary gland. After Cushing. become manifested physiologically [functionally] and morpho- logically [structurally] in the offspring.” The above summary adumbrates the lines along which some of the chemical interactions, if not causes, of mammalian ey- olution may be investigated during the present century. The cause of different bodily proportions, such as the very long neck of the tree-top browsing giraffe, is one of the classic problems of adaptation. In the early part of the nineteenth century Lamarck (p. 143) attributed the lengthening of the neck 250 THE ORIGIN AND EVOLUTION OF LIFE to the inheritance of bodily modifications caused by the neck- stretching habit. Darwin attributed the lengthening of the neck to the constant selection of individuals and races which were born with the longest necks. Darwin was probably right. This is an instance where length or shortness of neck is ob- viously a selective survival character in the struggle for existence, because it directly affects the food supply. But there are many other changes of proportion in mam- mals, which are not known to have a selective survival value. We may instance in man, for example, the long head-form Fic. 119. RESULT oF REMOVING THE (dolichocephaly) and the broad THYROID AND PARATHYROID GLANDS. head-form (brachycephaly), or (Right.) Normal sheep fourteen months old. the long-fingered form (dolicho- (Left.) A sheep of the same age from dactyly) and the short-fingered which the thyroids and parathyroids . were removed twelve months previ- form (br achydactyly), which ously. have been interpreted as con- After Sutherland Simpson. genital characters appearing at birth and tending to be transmitted to offspring. Brachy- dactyly may be transmitted through several generations, but until recently no one has suggested what may be its possible cause. . It has now been found! that both the short-fingered con- dition (brachydactyly) and the slender-fingered condition may be induced during the lifetime of the individual in a previously healthy and normal pair of hands by a diseased or injured con- dition of the pituitary body at the base of the brain. If the 1 Cushing, Harvey, 1911, pp. 253, 256. MODES OF EVOLUTION 251 secretions of the pituitary are abnormally active (hyperpitui- tarism) the hand becomes broad and the fingers stumpy (Fig. 118, B). If the secretions of the pituitary are abnormally re- duced (hypopituitarism) the fingers become tapering and slender (Fig. 118, C). Thus in a most remarkable manner the internal secretions of a very ancient ductless gland, attached to the brain and originating in the roof of the mouth in our most remote fish-like ancestors, affect the proportions both of flesh and bones in the fingers, as well as the proportions of many other parts of the body. Whether this is a mere co- incidence of a heredity-chro- Fic. 120. Resurr or REMOVING THE PITUITARY Bopy. matin congenital character 8 (Right.) Normal dog twelve months with a mere bodily chemical old. : (Left.) A dog of the same age and litter messenger character it would from which the pituitary body was be premature to say. It cer- removed at the age of two months. : ; ; After Aschner. tainly appears that chemical in- teractions from the pituitary body control the normal and ab- normal development of proportions in distant parts of the body. CHIEF MopES OF EVOLUTION OF MAMMALIAN CHARACTERS What we have gained during the past century is positive knowledge of the chief modes of evolution; we know almost the entire history of the transformation of many different kinds of mammals. These modes as distinguished from the unknown causes are expressed in the following general laws: first, the Jaw of con- tinuity; Natura non facit saltum, there is prevailing continuity 252 THE ORIGIN AND EVOLUTION OF LIFE in the changes of form and proportion in evolution as in growth. Second, the Jaw of rectigradation, under which many important new characters appear definitely and take an adap- tive direction from the start; third, the /aw of acceleration and retardation, witnessed both in racial and individual develop- ment, whereby each character has its own velocity, or rate of development, which displays itself both in the time of its origin, in its rate of evolution, and its rate of individual development. This last law underlies the profound changes of proportion in the head and different parts of the body and limbs which are among the dominant features of mammalian evolution. In the skeleton of mammals very few new characters originate; most of the changes are in the loss of characters and in the profound changes of proportion. For example, by the addi- tion of many teeth and by stretching or pulling, swelling or contracting, the skeleton of a tree shrew may almost be trans- formed into that of a whale. The above laws are the controlling ones and make up four- fifths of mammalian evolution in the hard parts of the body. So far as has been observed the remaining fifth or even a much smaller fraction of mammalian evolution is attributable to the law of saltation, or discontinuity, namely, to the sudden appearance of new characters and new functions in the hered- ity-chromatin. For example, the sudden addition of a new vertebra or vertebre to the backbone, which gives rise to the varied vertebral formule in different orders and even the dif- ferent genera of mammals, or the sudden addition of a new tooth are instances of. saltatory evolution in the hard parts of the body. There are also many instances of the sudden appearance of new functional, physiological, or physicochem- ical characters, such as immunity or non-immunity to certain diseases. ADAPTATION TO ENVIRONMENT 253 RESPONSES OF MAMMAL CHARACTERS TO CHANGING ENVIRONMENT Buffon was the first to observe the direct responses of mam- mals to their environment and naturally supposed that en- vironment was the cause of animal modification, chiefly in adaptation to changes of climate. It did not occur to him to inquire whether these modifications were heritable or not, any more than it did to Lamarck. It is now generally believed that these reactions are for the most part modifications of the body cells and body chro- matin only, which give rise to what may be known as environ- mental species, as distinguished from true chromatin species which are founded upon new or altered hereditary characters. Of the former order are many geographic varieties and doubtless many geographic species. These visible species of body cell characters are quite distinct from the invisible species of heredity-chromatin characters. Both occur in nature. Geologic and secular changes of environment have preceded many of the most profound changes in the evolution of the mammals, which interlock and counteract with their physical and life environments quite as closely as do the reptiles, am- phibians, and fishes; yet a very large part of mammalian evo- lution has proceeded and is proceeding quite independently of change of environment. Thus environment holds its rank as one of the four complexes of the causes of evolution instead of being the cause par excellence as it was regarded in the brilliant speculations of Buffon. The interlocking of mammals with their life environment is extremely close, namely, with Bacteria, Protozoa, Insecta, and many other kinds of Invertebrata, with other Vertebrata, as well as with the constantly evolving food supply of the plant 254 THE ORIGIN AND EVOLUTION OF LIFE world; consequently the vicissitudes of the physical environ- ment as causes of the vicissitudes of the life environment of mammals afford the most complex examples of interlocking which we know of in the whole animal world. In other words, the mammals interlock in relation to all the surviving forms of the life which evolved on the earth before them. Although suggested nearly a century ago by Lyell, the demonstration is comparatively recent that one of the principal causes of the extinction of certain highly adaptive groups of mammals is their non-immunity to the infections spread by Bacteria and Protozoa.! Thus a change of environment and of climate may not affect a mammal directly but may profoundly affect it in- directly through insect life. These closely interlocking relations of the mammals with their physicochemical environment and their life environment have been subject to constant disturbances through the geo- logic and geographic shifting of the twelve or more habitat zones which they occupy. Yet the earth changes during the Tertiary, the era during which mammalian evolution mainly took place, were less extreme than those during Mesozoic and Paleozoic time. This is because the trend of development of the earth’s surface and of its climate during the past 3,000,000 years has been toward continental stability and lowering of general temperature in both the northern and southern hemi- spheres, terminating in the geologically sudden advent of the Glacial Epoch, with its alternating periods of moisture and aridity, cold and heat, which exerted the most profound influ- ence upon the food supply, insect barriers, and other causes affecting the migrations of the Mammalia. These causes com- pletely change the general aspect of the mammalian world in 1 For the history and discussion of this entire subject see Osborn, H. F.: ‘“‘The Causes of Extinction of Mammalia,” Amer. Naturalist, vol. XL, November and December, 1906, Ppp. 769-795, 829-859. ADAPTATION TO ENVIRONMENT 255 the whole northern hemisphere, South America, and Australia, and leave only the world of African mammalian life untouched. The water content of the atmosphere during the 3,000,000 years of the Age of Mammals has tended toward a repetition of the environmental conditions of Permian and Triassic times in the development of areas of extreme humidity as well as areas of extreme aridity, interrupted, however, by widespread humid conditions in the Pleistocene Epoch. Marine invasion of the continents of Europe and North America, while far less ex- treme than during Cretaceous time, has served to give us the complete history of the littoral and marine Mollusca, both in the eastern and western hemispheres, which is the chief basis of the geologic time scale as discovered in the Paris basin by Brogniart at the beginning of the eighteenth century. The clearest conception of the length of Tertiary time is afforded (Fig. 121) by the completion in Eocene time of the Rocky Mountain uplift of America and the eastern Alps of Europe, by the elevation of the Pyrenees in Oligocene time, by the rise of the wondrous Swiss Alps between the Oligocene and Miocene Epochs, and finally by the creation of the titanic Himalaya chain in the latter part of Miocene time. Through the phenomena of the migration of various kinds of mammals from continent to continent, we are able to date with some precision the rise and fall of the land bridges and the alternating periods of connection and separation of the two northern continental masses, Eurasia and America, as well as of the northern and southern continents. Few writers maintain seriously for Tertiary time the “‘equatorial theory’’ of connection between the eastern and western hemispheres such as figures largely in the speculations of Suess, Schuchert, and others in relation to plant and animal migrations of Paleozoic and Mesozoic time. The less radical “bipolar theory” that 256 THE ORIGIN AND EVOLUTION OF LIFE the eastern and western hemispheres were connected both at the north pole and at the south pole, or through Arctic and Antarctic land areas, still has many adherents, especially in GLACIAL SQUAT Rv d ATERNARY OS | GLACIAL HIMALAYAS ie aT AGE : F 2 O SWISS ALPS : Berzelius, Einige Ideen iiber eine bet der Bildung organischer Verbindungen in der lebenden Natur wirksame aber bisher nicht bemerkte Kraft. Berzelius u. Woehler, J ahresbericht, 1836. APPENDIX 287 affinity, another force is active in chemical reactions: this he called cata- lytic force. As an example he used Kirchhoff’s discovery of the action of dilute acids in the hydrolysis of starch to dextrose. In this process the acid is not consumed, hence Berzelius concluded that it did not act through its affinity, but merely by its presence or its contact. . . . He thensuggests that the specific and somewhat mysterious reactions in living organisms might be due to such catalytic bodies as act only by their presence, without being consumed in the process. He quotes as an example the action of diastase in the potato. ‘In animals and plants there occur thousands of catalytic processes between the tissues and the liquids.’ The idea of Berzelius has proved fruitful. . . . We now know that we have no night to assume that the catalytic bodies do not participate in the chemical reaction because their quantity is found unaltered at the end of the reac- tion. On the contrary, we shall see that it is probable that they can ex- ercise their influence only by participating in the reaction, and by form- ing intermediary compounds, which are not stable. The catalyzers may be unaltered at the end of the reaction, and yet participate in it. “Tn addition we owe to Wilhelm Ostwald! the conception that the cata- lyzer does not as a rule initiate a reaction which otherwise would not occur, but only accelerates a reaction which otherwise would indeed occur, but too slowly to give noticeable results in a short time.” NOTE V THE CAUSES OR AGENTS OF SPEED AND ORDER IN THE REACTIONS OF LIVING BODIES—ENZYMES, COLLOIDS, ETC.’ “There is still another feature of cell chemistry which must strike even the most superficial observer, and that is the speed with which growth and the chemical reactions occur in it. ... Starch boiled with water does not easily take on water and split into sweet glucose, but in the plant cell it changes into sugar under appropriate conditions very rapidly. How does it happen then that the chemical changes of the foods go on so rapidly in living matter and so slowly outside? ‘This is owing to the fact, as we now know, that living matter always contains a large number of sub- stances, or compounds, called enzymes (Gr. em, in; zyme, yeast; in yeast) because they occur in a striking way in yeast. These enzymes, which are probably organic bodies, but of which the exact composition is as yet unknown, have the property of greatly hastening, or as is generally said, catalyzing, various chemical reactions. The word catalytic (kata, down; lysis, separation) means literally a down separation or decomposition, but 1Ostwald, W., Lehrbuch der allgemeinen Chemie, vol. II, 2d part, p. 248, 1902. 2 Mathews, Albert P., Physiological Chemistry, pp. 10-12. 288 APPENDIX it is used to designate any reaction which is hastened by a third substance, this third substance not appearing much, if at all, changed in amount at the end of the reaction. Living matter is hence peculiar in the speed with which these hydrolytic, oxidative, reduction, or condensation reactions occur in it; and it owes this property to various substances, catalytic agents, or enzymes, found in it everywhere. Were it not for these sub- stances reactions would go on so slowly that the phenomena of life would be quite different from what they are. Since these catalytic substances are themselves produced by a chemical change preceding that which they catalyze, we might, perhaps, call them the memories of those former chem- ical reactions, and it is by means of these memories, or enzymes, that cells become teachable in a chemical sense and capable of transacting their chemical affairs with greater efficiency. Whether all our memories have some such basis as this we cannot at present say, since we do not yet know anything of the physical basis of memory. “Living reactions have one other important peculiarity besides speed, and that is their ‘orderliness.’ The cell is not a homogeneous mixture in which reactions take place haphazard, but it is a well-ordered chemical factory with specialized reactions occurring in various parts. If proto- plasm be ground up, thus causing a thorough intermixing of its parts, it can no longer live, but there results a mutual destruction of its various structures and substances. ‘The orderliness of the chemical reactions is due to the cell structure; and for the phenomena of life to persist in their entirety that structure must be preserved. It is true that in such a ground- up mass many of the chemical reactions are presumably the same as those which went on while structure persisted, but they no longer occur in a well-regulated manner; some have been checked, others greatly increased by the intermixing. This orderliness of reactions in living protoplasm is produced by the specialization of the cell in different parts. ... Thus the nuclear wall, or membrane, marks off one very important cell region and keeps the nuclear sap from interacting with the protoplasm. Pro- found, and often fatal, changes sometimes occur in cells when an admix- ture of nuclear and cytoplasmic elements is artificially produced by rup- ture of this membrane. Other localizations and organizations are due to the colloidal nature of the cell-protoplasm and possibly to its lipoid char- acter. By a colloid is meant, literally, a glue-like body; a substance which will not diffuse through membranes and which forms with water a kind of tissue, or gel. It is by means of the colloids of a protein, lipoid, or car- bohydrate nature which make up the substratum of the cell that this localization of chemical reactions is produced; the colloids furnish the basis for the organization or machinery of the cell; and in their absence there could be nothing more than a homogeneous conglomeration of re- actions. The properties of colloids become, therefore, of the greatest APPENDIX 289 importance in interpreting cell life, and it is for this reason that they have been studied so keenly in the past ten years. The colloids localize the cell reactions and furnish the physical basis of its physiology; they form the cell machinery.” NOTE VI INTERACTIONS OF THE ORGANS OF INTERNAL SECRETION AND HEREDITY! The following table expresses the action of some of the organs of internal secretion: On PROTEIN METABOLISM Stimulating Inhibiting (accelerating) (retarding) Thyroid Pancreas Pituitary body Parathyroids Suprarenal glands and other adrenalin-secreting tissue Reproductive glands On CALcIuM RETENTION Favorable to Inhibiting Pituitary body Reproductive glands Thyroids Parathyroids The facts that are here presented show that the action of the anterior lobe of the pituitary body upon the chemical changes or transformations taking place in the vertebrate organism or in any of its cells strongly re- sembles the action of the thyroid, although less pronounced. It is clear from its relation to the reproductive organs, to the adrenalin-secreting tissues of the suprarenal glands and other similar tissues, and to the formation of an abnormal amount of glucose in the urine, that the pituitary body, thyroids, reproductive glands, suprarenals, and thymus are a closely related series of organs which mutually influence each other’s growth. Important as these organs are, it must be remembered that the co- ordination of all the chemical changes and transformations within the body—all processes of renewal, change, or disorganization such as respira- tion, nutrition, excretion, etc.—embraces every organ in it. The body is an organic whole, and the so-called organs of internal secretion are not unique, but the bones, muscles, skin, brain, and every part of the body are furnishing internal secretions necessary to the development and proper 1 Mathews, Albert P., 1916. Physiological Chemistry, pp. 649, 650 (modifled). 290 APPENDIX functioning of all the other organs of the body. A scheme of the organs of internal secretion, to be complete, must embrace every organ, and so far only the barest beginning has been made in this study so important, so necessary for the understanding of development and inheritance. Prob- lems of development and inheritance cannot be solved until these physio- logical questions are answered. As for the bearing of these processes upon Heredity, the internal secre- tions of the body appear to Mathews to constitute strong evidence against the existence of such things as inheritance by means of structural units in the germ which represent definite characters in the body. We see in the internal secretions, he observes, that every character in the body involves a large number of factors (i. e., determiners). The shape and size of the body, the coarseness of the hair, the persistence of the milk-teeth, a ten- dency toward fatness—all these may easily depend on the pituitary body, on the thyroid, and on the reproductive organs, and these—in their turn —are but the expression of other influences played upon them by their surroundings and their own constitution. An accurate examination shows the untrustworthiness of any such simple or naive view as that of unit characters. NOTE VII TABLE—RELATIONS OF THE PRINCIPAL GROUPS OF ANIMALS REFERRED TO IN THE TEXT Phylum Class PAGES PROTOZOA ( 1Rhizopoda | Lobosa—A meba, etc........... O3ST12 1A ArIG (the simplest | Foraminifera (porous-shelled protozoa) animals) 32, 103, 115 { Radiolaria (siliceous-shelled protozoa)..... II5 | Mastigophora 2 ..dzsG nec cee eee ia ee £12,155 Infusoria—ciliatestetor 4. eae eee Sn ie SRI cies Pet LIT2,1rs | Sporozoa PORIFERA 1Calcarea Calcareous sponges | (sponges) | 1Non-Calcarea Siliceous Mae et Fh SPY ee pris, 130 Fibrous ee C@LENTERATA ( 1Hydrozoa Hydroids—millepores. .......0..00.se000- 113 Siphonophores Graptolithida 1Scyphozoa Jellyiishes 3 272 cu a5 a ee 120, 129, 130 1Actinozoa Sea-anemones, corals, sea-fans, etc........ 103 Ctenophora 1 Fossil and recent forms. All other classes listed are as yet unknown in the fossil state. APPENDIX Phylum PLATYHELMINTHES Class Turbellaria Trematoda Cestoda Nematoda Acanthocephala 1Chetognatha NEMATHELMINTHES TROCHELMINTHES Rotifera MOLLUSCOIDA 1Polyzoa Phoronida 1 Brachiopoda 1Asteroidea ECHINODERMATA _ { 1 Ophiuroidea 1Echinoidea 1Holothuroidea 1Crinoidea 2Cystoidea | 2Blastoidea ANNULATA ( 1Chetopoda (true worms) Gephyrea Hirudinea Branchiata ( 1Crustacea ARTHROPODA ? Trilobita 1Xiphosura Tracheata Onychophora 1Myriapoda 1 Arachnoidea | 1Insecta MOLLUSCA 1Pelycypoda 1Amphineura 1Gastropoda 1Scaphopoda 1 Cephalopoda 1 Fossil and recent forms. 2 Extinct fossil forms. 291 PAGES Flat worms Flukes Tape-worms Round worms Hook-headed worms A TTOWSWOLINS are cine eee peewee F20n1 20 Wheel-animalcules Bryozoa (moss animals) amp shiellsamm seer ance 120,123, 130, 138, 140 meaestars (SLariiSUCs mnt tet ee ian ee. 136; 172 Brittle stars SEA-UPCHING se net amen, oc SmeR ANE ee Suh ae 94 SeA-CUCUIIDEL Setar ei araee a haere Mie L25,427 Sea-lilies (stone-lilies).............-.04+ 66 primitive echinoderms Sea-worms, earthworms................ 128 Sipunculids Leeches Crabs, lobsters, shrimp, barnacles, ostra- COUT Er Ti tir te sit aust aay E2041 24) 534 Trilobites, eurypterids=>% 2). £20. feo; 1b 320133 Horseshoe-crabsvaee a ees ee 124,125,132 Peripatus Centipedes, millepedes Spiders, scorpions, mites, ticks... .130, 132, 136 ANSECtSee ene Ae arsteate t Seite 105, 130, 136, 254 Glams, OVsters, Mussels: cuts. ss maces 130 Chitons Limpets, snails, slugs, sea-hares, etc... .120, 130 Tusk-shells Nautilus, cuttle-fish, ammonites. . .130, 137-139 All other classes listed are as yet unknown in the fossil state. 292 APPENDIX Phylum Class PAGES CHORDATA Sub-phylum (delochordaeenee ts ser see tees Balanoglossus, etc.—worm-like chordates Urochordavtrer oon ee eee Ascidians, salps, etc.—sessile and secon- | darily free-swimming marine chordates, 162, 168 Acrania Amphioxus (lancelets) *....5....:....5.- 162 Cyclostomata Lampreys;hags#e 09. ee 168 1 Pisces ( Ostracodermata (Paleeozoic shelly-skinned (fishes) | eishes steko Se peat ch reehee aN ee 161, 165-168 Vertebrata | | Arthrodira (Paleozoic joint-necked fishes) 166-168 | Elasmobranchii—sharks, rays, chimzeroids | 161, 167-169 Dipnot (ung-fishes)y ise ease ee 168,170, 172 AL CleoStom Yim erin eka ae eee 172 | lobe-finned ganoids (Crossopterygii) | 168, 172, 174 | true ganoids—sturgeons, garpike, | DOWNS SeLC ween aen ue, eres 168, 170 | teleosts (bony fishes)........ .168, 170, 175 | 1 Amphibia Frogs, toads, newts, mud-puppies, Stego- cephalia’ etcleiay vee ae ee 177-183 1 Reptilia Turtles, tortoises, tuateras, lizards, mosa- saurs, snakes, crocodilians, dinosaurs, mammal-like reptiles, ichthyosaurs, ple- siosaurs, pterosaurs (flying reptiles), etc. 184-226 1Aves Reptile-like birds (Arch@opteryx)...... 226-229 (birds) leModernizedbirdStes wu eee ee 227-231 “Ratite” birds—ostriches, moas, etc. 228, 229 “‘Carinate”’ birds—toothed birds and alltother birds weg. ae. oe eee 230, 231 | t 1Mammalia Monotremes_ (egg-laying mammals)— duck-bills “ete eee es oe ee 2255294 Marsupials (pouched mammals)—opos- sums, kangaroos, etc...... 235, 237, 243, 244 Placentals insectivores, carnivores, primates, ro- dents, bats, whales, artiodactyls (cattle, deer, pigs, antelopes, giraffes, camels, hippopotami, etc.), ungulates including proboscidea (mastodons and elephants) and perissodactyls (horses, tapirs, rhi- noceroses, titanotheres, etc.), and many other orders. 92 A se ee 259-274 1 Fossil and recent forms. 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Jbid., pp. 801-850. 1905 Les dinosauriens adaptés a la vie quadrupéde secondaire. Bull. Soc. Belge de Géol., de Paléontologie et d’Hydrologie, tome XIX, 1905, Mémoires, pp. 441-448. Heilmann, Gerhard. 1913. Vor Nuverende Viden om Fuglenes Afstamming. Dansk Ornitho- logisk Forenings Tidsskrift, January, 1915, Aarg. 7, H. I, II, pp. eel Ae , BIBLIOGRAPHY 305 Lull, Richard Swann. to15 ‘Triassic Life of the Connecticut Valley. State of Connecticut State Geol. and Nat. Hist. Survey, Bull. 24, 1915. Williston, Samuel W. 1914 Water Reptiles of the Past and Present. University of Chicago Press, Chicago, 1914. CHAPTER VIII Bacon, Francis, Lord Bacon, Baron Verulam and Viscount St. Albans. 1620 Novum Organum. English version, edited by Joseph Devey, M. A. P. F. Collier & Son, New York, rort. Brown, Amos Peaslee. 1909 ‘The Differentiation and Specificity of Corresponding Proteins and Other Vital Substances in Relation to Biological Classification and Organic Evolution: The Crystallography of Hemoglobins (with Reichert, Edward Tyson). See Reichert. Cushing, Harvey. 1912 The Pituitary Body and its Disorders, Clinical States Produced by Disorders of the Hypophysis Cerebri. Harvey Lecture, 1o10, amplified. J.B. Lippincott Co., Philadelphia and London, ror2. Dollo, Louis. 1906 = Le pied de l’ Amphiproviverra et Vorigine arboricole des marsupiaux. Bull. Soc. Belge de Géol., de Paléontologie et d Hydrologie, tome XX, 1906. Procés verbaux, pp. 166-168. Gregory, Wm. K. 1910. ©The Ordersof Mammals. Bull. Amer. Mus. Nat. Hist., vol. XXVII, February, rgto. Goodale, H. D. 1916 . Gonadectomy in Relation to the Secondary Sexual Characters of some Domestic Birds. Carnegie Institution of Washington, Publ. no. 243, Washington, 1916. Huxley, Thomas H. 1893 Darwiniana (vol. II of Essays). D. Appleton & Co., New York and London, 1893. Lillie, Frank R. 1917. The Free-Martin; a Study of the Action of Sex Hormones in the Foetal Life of Cattle. Jour. Experimental Zoology, July 5, 1917, PP. 371-452. 306 BIBLIOGRAPHY ‘Mathews, Albert P. 1916 ~=6©Physiological Chemistry, A Text-Book and Manual for Students. William Wood & Co., New York, 10916. Matthew, W. D. 1915 Climate and Evolution. Ann. N. Y. Acad. Sciences, vol. XXIV, February 18, 1915, pp. 171-318. Osborn, Henry Fairfield. 1897 Organic Selection. Sczence, October 15, 1897, pp. 583-587. 1910 6°’ The Age of Mammals in Europe, Asia, and North America. Mac- millan Co., New York, 1g1o. Reichert, Edward Tyson, and Brown, Amos Peaslee. 1909 The Differentiation and Specificity of Corresponding Proteins and Other Vital Substances in Relation to Biological Classification and Organic Evolution: The Crystallography of Hemoglobins. Car- negie Institution of Washington, Publ. no. 116, Washington, 19009. Russell, E. S. 1916 Form and Function, A Contribution to the History of Animal Morphology. John Murray, London, 1916. Scott, William B. 1913. A History of Land Mammals in the Western Hemisphere. Mac- millan Co., New York, 1913. APPENDIX Loeb, Jacques. 1906 The Dynamics of Living Matter. Columbia University Press, New York, 1906. 1916 The Organism as a Whole, from a Physicochemical Viewpoint. G. P. Putnam’s Sons, The Knickerbocker Press, New York and London, 1916. Mathews, Albert P. 1916 Physiological Chemistry, A Text-Book and Manual for Students. William Wood & Co., New York, 1916. INDEX A Acadia, 134 Acanthas pis, 167 AGCCeleraAtion ai0sa1 7,4105, 145, 4140, °233, 252, 268, 279, 280 Action and reaction, 5, 6, 12-23, 39, 53, 54, 58, 68, 69, 71, 77, 80, 88, 98, 100, 106, TIO. Shi PLEO, sl20, aT A215 tA 7 250, 152, 154, 160, 231, 242, 244-240, 271, 279-283 Adaptation, 7, 8, 10, 20, 23, 38, 46, 58, 143, 144, I5I-159, 174, 208, 225, 232, 236, 239-249, 253-259, 202, 266, 273, 275, 277, 281, 282; see Adaptive radiation, Convergence, Divergence, Food adapta- tions, Habitat adaptations; alternate, 201, 203, 236, 240, 243; convergent, 155 (Fig.), 200 (Fig.), 207 (Fig.); reversed, 201, 203, 204, 236, 240, 241, 260 Adaptive radiation, 89, 114, 118, 119, 121, 130, 131, 157-159, 168, 175, 180, 184, TSO5200, -101-194,* 2015-222, $227. 236— 239, 259, 274 Adirondacks, too Adult, 106, 111, 147 Africa, 82, 125, 183, 188, 194-196, 217, 225, 220,9237, 241,-201,-203,. 200+; see South Agassiz, Louis, 152 Aglaspide, 124 Air, 18, 22, 33; 37, 455 79, 84, 105, 106; see Atmosphere Aistopoda, 178 Alabama, 260 Alaska, 206 Alberta, 222, 223 Alge, 32, 33, 38, 45, 49, 50, 53, 64, 66, 67, 80, 90, OI, 99, 101-104, 105; blue-green, IOI, 102, 285, 286, see Cyanophycee; earth-forming, 103; limestone-forming, 118, 137; rock-forming, 103 Algomian, 50, 153 Algonkian, 50, 85, 86, 102-104, 120, 153, 256 Alligators, 186, 199 Allosaurus, 213 (Fig.), 221. Alpine, 83 Alps, 188, 255, 256 Aluminum, 33, 34, 54 Amalitzky, W., 191 Amblypoda, 259 America, 79, 164-166, 182, 190, 195, 237, 255, 266; see North, South Aminoacids, 86 Amiskwia sagittiformis, 129 (Fig.) Ammonia, 68, 83, 86 Ammonites, 130, 137-139 (Fig.), 181, 213, 291 Ammonites subradiatus, 138, 139 (Fig.) Ammonium salts, 84, 85 Ammonium sulphate, 82 Ameba, 57, 112, 116, 290; limax, 93 (Fig.); proteus, 112 (Fig.) Amphibamus, 178, 179 (Fig.) Amphibia, 131, 165, 172, 174, 177-183, 185, 186, 196, 292; see Amphibians Amphibians, 161, 163, 175, 177-183, 185, 190, 198-200, 210, 212, 231, 239, 246, 253, 260, 275; see Amphibia Amphioxus, 162 (Fig.), 168, 292; see Lance- lets Anchisaurus, 211 (Fig.), 213, 216 (Fig.) Angiosperms, 108 Anguilla, 174 Animals, 40, 41, 51, 53, 55, 56, 69, 70, 80, QI, 106-110, 285; air-breathing, 166, 185; bipedal 2137 216, 227 29480226, 9227. 229; experiments on, 74-79, 116, 117, 247, 250, 251; predaceous, 162, 169, 181, 190, 234; quadrupedal, 210, 216, 217, 219, 220, 224 Animikian, 50, 153 Ankylosaurus, 225 Annulata, 118, 128 (Fig.), 130, 131, 201; see Worms Anomodonts, 190, 191, 193 Anome pus, 211 (Fig.) Antarctic, 164, 166, 181, 185, 205 Antarctica, 256 Ant-eater, 259, 279; spiny, 235 (Fig.) Antelopes, 225, 266, 292 397 308 Antiarchi, 165-167 (Fig.) Antibodies, 73, 74 Antillia, 206 Antilocapra, 266 Antitoxin, 73, 74 Anura, 178 A patosaurus, 213 (Fig.), 219, 220 (Fig.), 221 Apes, 236, 237, 269, 274 Aphroditidz, 128, 129 Appalachian, 135, 136, 164, 181, 188, 256 A pus lucasanus, 124 (Fig.) Arabella opalina, 128 (Fig.) Arachnida, 125, 166; see Arachnids Arachnids, 130; see Arachnida Ar@oscelis, 186 (Fig.) Archean; 50, 100, 153/256 Archeoceti, 241 Archaeopteryx, 227, 228-230 (Figs.), 292 Archeeozoic, 34, 50, 82, 95, 153 Archegosaurus, 182 Archelon, 203 (Fig.), 206 Arctic Ocean, 206 Arctic seas, 134, 205 Argentina, 217 Argon, 41 Arid, 185, 197 Aridity, 107, 135, 180, 254, 258 Aristotle, 8, 9, 279 Armadillo, 148, 224, 259 Armature, 121, 132, 153, 154, 161, 164-166, 1605170;1582, 157,1202,,203% 224 3255270 Arrhenius, Svante A., 49, 54 Arsenic, 54 Arthrodira, 166, 167 (Fig.), 292; see Ar- throdiran fishes, Arthrodires Arthrodiran fishes, 172, 175; see Arthro- dira, Arthrodires Arthrodires, 134, 168-170; see Arthrodira, Arthrodiran fishes Arthropoda, 118, 130, 291; see Arthropods Arthropods, 124; see Arthropoda Articulates, 130, 132, 133 Ascidians, 162, 168, 292 Asia, 82, 237, 256, 261, 260, 274 Aspidosaurus, 182 Atmosphere, 9, 26, 28, 33, 34, 37, 39-42, 43-45, 52, 68, 86, 87, 99; 106, 255; see Air, Carbon dioxide, Volcanoes Atomic weight, 34, 55, 59, 67 Atoms, 39, 54, 56, 59, 60, 97, 98, 117 Australia, 180, 203, 237, 255, 262 Aye-aye, 150 Azotobacter, 86, 87 INDEX B Baboons, 239 Bacon, Francis, 12, 283 Bacteria, 23; 31-33, 371.39) 49) 42, 453 49- 51, 67, 80-93 (Fig.), 99, IOI, 105, IIo, TIT, 143). 253; 2254, %28034seee Monads; aérobic, 87; ammonifying, 84; anaérobic, 40, 42, 87, 89; antiquity of, 84, 85; cal- careous, 104; denitrifying, 85, 86, 91, 104; iron, 90, 118; luminous, 91; nitrifying, 37, 62, 82-86, 110; parasitic, 89; proto- trophic, 81; size of, 81; sulphur, 83, 90; symbiotic relations of, 82, 87, 89 Bacterium calcis, 90; B. radicicola, 87 Bahama Banks, Great, 90 Bain, Andrew Geddes, 189 Balenoptera borealis, 234 (Fig.) Balance, 16, 17, 91, 140, 233, 269, 280 Baldwin, J. Mark, 244 Baltic Sea, 188 Baptonodon, 205 (Fig.) Barathronus diaphanus, 173 (Fig.), 174 (Fig.) Barbados, 115 Barium, 33, 34, 36, 54, 66 Barnacles, 113, 134, 291 Barrell, Joseph, 62, 136, 213 Barus, Carl, 27 Bateson, William, 7, 145 Bats, 236, 239, 259, 292 Bears, polar, 239 Beaver, 239 Bechhold, Heinrich, 68 Becker, George F..26,°35; 36740 Becquerel, Antoine Henri, 11 Beebe, C. William, 228 Belgium, 222 Beltina danat, 121 Bergson, Henri, 10 Bernissart, 222 Bert, Paul, 111 Berthold, 77 Berzelius, Jons Jakob, 57, 286, 287 Beyjerinck, 83 Bicarbonates, 42, 59 Bighorn Mountains, 160 Big Tree, 96 Bion, 6 Birds, 67, 131, 161, 211, 226-231, 232, 247, 275, 292; aquatic, 230, 231; relation of plants to, 105; toothed, 227, 230, 292 Birkenia, 165 Bison, 225 INDEX Bivalves, 134, 136 Black Hills, 161, 218 Blood, 15, 37, 63, 66, 72, 74, 79, 192, 232, 247 Body, 197, 207-209, 212, 219, 224-226, 230-232, 230, 252, 261, 289, 290; -cell, see Cell; -form, 163 (Fig.), 175, 179 Bohemia, 177 Bone, 10, II, 64, 221, 226, 227, 265, 289 Boron, 36, 54 Bothriolepis, 165-167 (Fig.), 170 Boveri, Th., 92, 94 Bowfin, 168, 170, 292 Brachiopoda, 131, 291; see Brachiopods, Lamp-shells Brachiopods, 65, 120, 121, 123 (Fig.), 130, 134, 138, 171; see Brachiopoda, Lamp- shells Brachiosaurus, 217, 219 (Fig.) Brachycephaly, 250 Brachydactyly, 75, 76, 249, 250 ISLA OF LO 2112270 252° ORT aco: 289 Branner, J. C., 83 Brazil, 207 British Isles, 171 Brogniart, Alex., 255 Bromine, 33, 37; 54, 66 Brontosaurus, 219, 220 Brontotheriine, 149 Brontotherium, 263 (Fig.), 264, 270; platy- ceras, 264 (Fig.) Broom, Robert, 189 Brown, Amos Peaslee, 79, 247 Brown, Barnum, 223 Brown-Sequard, Charles Edward, 77 Buffon, Georges Louis Leclerc, Comte de, 2, 253 Bunodes, 154 Burgessia bella, 124 (Fig.) Biitschli, O., 67 Cc Cacops, 182 (Fig.) Calamoichthys, 174 Calcareous, alge, 103; hacteria, 104; ooze, 198; skeleton, 115 Calcium, 33, 35-37, 46, 47, 54, 55, 63, 64, 65, 67, 68, 71, 82, 84, 90, 240, 289 California, 94, 96, 97 Calkins» Gary, N., 111 Camarasaurus, 219 (Fig.) 399 Cambrian, 28, 29, 38, 50, 102, 118, 122, 123, 120s 2Oe1 Si. 130 134. t acer coRT eo TOE, TOS 176," 103, .:240; 250; ) early, » 123° Lower, 121; mid-,'120; 121, 123,, 120, 130; Middle, 118, 119; post-, 153; pre-, 20eE Ope O 5007 103, I 7 1a el 20M Date 12544130) 132)01345°135,.052, 153, 240 Camels, 262, 292 Campbell, William Wallace, 3, 4 Camptosaurus, 221 (Fig.), 222 Canada, 165, 223 Canadia, 129; spinosa, 128 (Fig.) Canon City, Colorado, 160, 161 Capybara, 239 Carbohydrates, 52, 58, 72, 87, 89, 100, 248, 280, 288 Carbon, 9, 31-33, 37, 40, 41, 46, 47, 50-55, 58, 62, 63, 67, 70, 82, 83, 86-88, 99-101; dioxide, 40-42, 45, 52, 64, 68, 70-72, 82, 86, 99, 285, 286 Carbonaceous, limestones, 32; matter, 40; meteorites, 47; shales, 32 Carbonates, 54, 65, 90, 120, 246; calcium, 104, 153} Magnesium, 104 Carbonic acid, 9, 42, 59 Carboniferous, 126, 135, 137, 153, 161, 168, 169, 177-180, 193, 194, 211, 227, 236, 256 Carnivora, 259; see Carnivores, Food adaptations Carnivorés, 236, 237, 258, 259, 292; see Food adaptations, Carnivora Carnot; Nw ke. Sadi, 12.14 Case, I.-C: 180; 186 Cassowaries, 230 Catalysis, 54, 57, 58, 106, 150, 286, 287; see Enzymes, Berzelius on, 57 Catalyzer, 57, 58, 69, 72, 82, 116, 246, 280, 287; see Enzymes Catfishes, 175 Catskill delta, 134 Cattle, 225, 292 Cell, 22, 68, 73, 78, 80, 82, 86, 88, 91-99, 103, II14, 116, 286, 288, 289; see Germ; body-, 04, 98, 142-140, 150, 244, 253, 283; differentiation, 87, 93; division, 61, 116; germ-, 77; 78, 94-96, 98, 105, 144, nucleus, 63, 73) 87, 92-94, 97, 102, I14, 116; wall, 87, 288 Cellulose, 52, 101 Cenozoic, 135, 161, 168, 178, 193, 236 Cephalas pis, 175 Cephalopoda, 291; see Cephalopods Epo Cephalopods, 130, 181, 213; see Cepha- lopoda Ceratodus, 172 Ceratopsia, 224 (Fig.) Cetacean, 200, 236 Chetognatha, 129 (Fig.), 131, 291; see Cheetognaths Cheetognaths, 120, 129; see Cheetognatha Chalk, 206 Chalones, 74, 77, 78, 106, 150, 246, 280 Chameleons, 239 Chamberlin, Thomas Chrowder, 3, 25, 26, 34 Champsosaurus, 199 (Fig.) Characters,'4,270,4 0Ss.10 7 pul 17s oo tao. 145-152, 198, 207, 208, 233, 238-240, 242, 244-246, 250-253, 258, 259, 263, 205, 208; 270, 2715 275-279) 200 Character velocity, 107-109, 149, 150, 232, 233, 252, 250, 205, 268, 279 Cheiracanthus, 170 (Fig.) Cheirole pis, 170 (Fig.) Cheiromys, 150 Chelonia, 201-203 Chemical, compounds, 4, 17, 32, 35, 36, 38, 45, 54; 56, 62, 79; 81; elements, 4-6, 14, 18, 19, 30, 31, 33-36, 45, 52, 54, 56, 59; evolution of, 3; messengers, 6, 15, 60, 71-79), 88, 89, 98, 106, 107, 109, 150, 233, 246, 251, 278, 279, 282, 283; Huxley on, 57, 72 Chilonyx, 187 Chitin e132 5512355153 Chitinous, armature, 121, 132, 165, 246; shield, 124 Chlamydomonas, 113 Chlamydoselache, 169 Chlorine, 33; 36, 37) 47) 545 66, 82 Chlorophycee, 104 Chlorophyll, 40-42, 48, 51-53, 64, 65, 71, 81, 99-101, 102, 118, 286 Chlorophyllic organs, 105 Chordata, 153, 292; see Chordates Chordates, 50, 153, 161, 246, 2092; see Chordata Chromatin, 63, 78, 85, 91-99, 110, 116, 141- 148, 154, 158, 231, 253, 263, 268; body-, 21, 77; 232, 253; heredity-, 21-23, 77,95; 98, 00, FOO-108,. 710, 114, TIO; 117, 142, 143, 145, 147, 151, 177, 198, 199, 233, 240-246, 251-253, 266, 278 Chronology, 27-29, 36, 256 Ciliata, 115; see Ciliate INDEX Ciliate, 112 (Fig.), 119, 290; see Ciliata Cirripedes, 134 Cladoselache, 167 (Fig.), 168 Clarke, Frank Wigglesworth, 3, 32, 36, 41, 63, 68, 83, 103, 104 Claws, 184, 215, 227 Clepsydrops, 188 Clidastes, 210 Clostridium, 87 Club-mosses, 180 Coal, 135, 137 Coal measures, 177 Coast Range, 135, 218; see Pacific Coast Range Cobalt, 54 Coccosteus, 170 (Fig.) Coelenterata, 118, 131, 290; see Ccelen- terate Coelenterate, 113, 130; see Coelenterata Cold, 49, 180, 254 Colloids, 39, 54, 58, 59, 68, 84, 288, 289 Colorado, 217, 220 Comanchean, 153, 161, 168, 178, 193, 211, O17 M21 Oy 2270230 Combustion, 40, 52, 55, 61 Comets, 47 Compensation, 16, 158, 215, 280 Competition, 21, 22, 69, 147, 188 Condylarthra, 259 Congo, 248 Conifers, 108, 134, 212, 213 Connecticut valley, 210-213 Continental, depression, 135, 136; seas, 134, 198, 206, 210; waters, 130 Continents, 25, 26, 35, 36, 41, 181 Continuity, 251, 276, 277 Convergence, 154, 155, 157, 165, 173 Cooperation, 16, 69, 145, 240 Coordination, 16, 69, 106, 145, 160, 240, 246 Cope, Edward Drinker, 143, 144, 177, 186, TSS gt 00,9210. rea 2 las Copper, 36, 54, 66, 67, 71 Corals, 103, 137, 213, 290 Cordilleran seas, 205 Cordilleras, 122 Correlation, 69, 106, 143, 240, 246, 280 Coryphodon, 259 (Fig.) Corythosaurus, 223 (Fig.) Cotylosauria, 185, 191; see Cotylosaurs Cotylosaurs, 187, 190, 193; see Cotylo- sauria Coulter, Merle, 108 INDEX Coutchiching, 50, 153 Crab, 291; see Horseshoe crab Credner, Hermann, 177 Cretaceous, 50, 194, 196-198, 205, 208-210, 27210) 221,222, 224,230, 725519250, aor; lower, 135;.153aL01,,105,175;.102; DOs oll w2Ts,) 217 -210,0027, 2307, mid- dle, 224; upper, 135, 137, 153, 161, 168, Bs 10400 520018 202.9 205 200" 210; BIT, 213, 214; 222, 223,227, 930, 230, 250 Cricotus, 178, 181, 182 (Fig.), 200 (Fig.), 210 Crinoids, 66 Crocodiles, 193, 194, 199-201, 211, 212, 227, 231; see Crocodilia, Crocodilian Grocodiligiy 193, *100,.201, 210, «231; see Crocodiles, Crocodilian Crocodilian, 200, 292; see Crocodiles, Croc- odilia Crossopterygia, 174, 186 Crossopterygii, 168, 292; see ganoids, lobe- finned SrUstacea £20, 121, 127, 141, 193,134" 291; see Crustacean Crustacean, 124, 125, 130; see Crustacea Cryptocleidus oxoniensis, 207 (Fig.) Cryptozoon Ledge, 102 Cryptozoon proliferum, 102 (Fig.) Cunningham, J. T., 77, 78, 144 Curie, Pierre, 11 Cuvier, Baron Georges L. C. F. D., 24, 51, 95, 190, 237, 240, 279 Cyanophycee, 92, 101, 103; see Algz, blue- green Cycads, 108, 212, 213 Cyclostomata, 292; see Cyclostomes Cyclostomes, 168; see Cyclostomata Cymbospondylus, 200 (Fig.), 205 (Fig.), 210, 213 Cynodonts, 190-192, 236 Cynognathus, 190 (Fig.) D Dactylometra quinquecirra, 130 (Fig.) Dadoxylon, 134 Dahlgren, Ulric, 44 Dakota, 222; see South Daphnia, 111, 113 Darwin, Charles, 2, 7, 8, 20, 23, 24, 27, 118, 138, 140, 144, 145, 153, 157, 235, 240, 250, 276 Darwin, Sir George, 27 311 Deer, 225,202 Defenses 1755 120,131, 152, 160, 165.7187. 202, BeAr 2e 5.240, 200,203 Delta, 134, 189, 198, 262 Democritus, 7, 8 Dendrolagus, 203, 243 Deperet, Charles, 219 Deposition, 65, 90 Descartes, René, 2 Devonian, 50, 122, 123, 133-136, 138, 153, POM ELO5—1 72, 75-1703) 10350250 Diadectes, 187 (Fig.) Diatoms, 32, 33, 90, 104, 286 Didelphys, 235 (Fig.) Differentiation, 23, 87, 93, 157, 249; chem- ical, 78, 79 Difflugia, 117 Digestion, 61, 66, 280 Digestive organs, 129 Digits, 206, 268 Dimetrodon, 188, 189 (Fig.) Dingo, 247 Dinichthys, 175; intermedius. 166 (Fig.), 167 Dinocephalians, 190 Dinoceras, 259 Dinosauria, 210-225; see Dinosaurs Dinosaurs, 142, 186, 191, 193-197, 210-225, 227, 229, 276, 292; carnivorous, 210-216, ZO m2 25 A CLICK Dil ee OUT an a2 2 8223. herbivorous, 216-225; ‘‘ostrich,” 213- 215 (Figs.); “tyrant,” 224 (Fig.) Diplacanthus, 167, 170 (Fig.) Diplocaulus, 179 (Fig.), 180 (Fig.), 182 Diplodocus, 219 (Fig.), 221 Dipnoi, 168, 170, 172, 292; see Fishes, lung- Dipterus, 170 (Fig.) Divergence, 157, 270 Dog, 247 Dohrn, Felix Anton, 246, 279 Dolichocephaly, 250 Dolichodactyly, 76, 249, 250 Dollo, Louis, 202, 209, 243 Dolphin, 200, 204, 205, 230 Driesch, Hans, 10, 73 Dromosaurs, 190 Dugongs, 269 Dynamics, 12; see Thermodynamics E Earth, 4, 18, 22, 24-34, 39, 45; 52, 79, 80- 84; age of, 25, 27-29; crust, 61, 65, 90, 118, 136; evolution of, 3, 7; heat of, 25- 212 27, 45, 48, 56, 84, 110; stability of, 25, 34; surface of, 25-27, 30, 31, 33, 44; 45 Echidna, 235 (Fig.) Echinodermata, 118, 130, I31, 291; see Echinoderms Echinoderms, 66, Echinodermata Edaphosaurus cruciger, 188, 189 (Fig.) Edentates, 236, 237, 259 Fel>173;/176 Egypt, 269 Ehrenberg, D. C. G., go Ehrlich, Paul, 57, 247 Elasmobranchii, 292; see Elasmobranchs Elasmobranchs, 168; see Elasmobranchii Elasmosaurus, 208 (Fig.) Eldonia ludwigi, 126, 127 (Fig.) Electric organs, 176 Electricity, see Energy, electric, of elec- tricity Electrons, 59, 97, 98, IOI, I17 Electroplaxes, 176 Elements, chemical, 4-6, 14, 18, 19, 30, 31, 33-36, 45, 52, 54, 56, 59; evolution of, 3; life, see Life elements; metallic, 47, 48, 54, 55, 64, 88; non-metallic, 47, 54, 55, 66, 88; radioactive, 28, 56 Elephant, 219, 261, 264, 269-273, 279, 2923 see Elephas Elephas, 269 (Fig.), 270; see Elephant; primigenius, 271 (Fig).; see Mammoth, woolly Elimination, 99, 137, 220, 271; see Extinc- tion Elpidiide, 126 Embryo, 106, 108 Embryonic stages, 106, 108, I1I Empedocles, 7, 8 Endocrine organs, 74 Endothiodon, 190 (Fig.) Energy, T, 3, 4, 10, II, 17, 18, 20, 79, OI, 05;:100, 1O5=FO7, TIO LI AA PAGS gol capture’ of) 14,016, T7448" 80,6 7.915 2; chemical, 14, 44, 113; concept of life, ro- 23,2815 conservation) Of, £23/134°15,.18, 51, 53; degradation of, 11, 14, 53; dis- sipation of, 11, 14, 15; electric, 39, 48, 52, 53, 55; see Energy of electricity, Ioniza- tion; four complexes of, 18-23, 98, 99, 145, 147, 154; kinetic, 13,14, 21, 285; latent, 19, 278, 280; life a new form of, 5, 12; life due to an unknown, 6, 12; life- less, 48, 57; living, 48, 51, 55; mechan- 130, Veh 7 a) 201s wysce INDEX ical, 14; of electricity, 12, 176; see En- ergy, electric; Ionization; of gravitation, TT, 2nd; Olsheat, 12 314 53 CON tOCe 113, 254, 280; see Cold; Earth, heat of; Solar heat; Sun, heat of; Temperature; Volcanic heat; of life, 11; of light, 12, 43- 45, 48, 40, 71, 99, 100, IOI, 113; see Heliotropism, Light, Phosphorescence; of motion, 10, 12, 14, 53, 280; see Motion, Newton’s laws of; Velocity; of radio- activity, 26; of reproduction, 18; po- tential, 13, 15, 19, 21, 285; physiochem- ical, 20, 22, 48, 58, 95, 99, 150; radiant, Il, 14, 41,285; release 0l,14,-L 7511005 53 61, 80, 152, 280, 285; storage of, 14, 16- 18, 80, 87, 152, 280, 285; transformation of, 11, 13-15, 17, 278-280 England, 207 Environment, 20, 70,.120; 135, 1374 £42, 143, 147, 177, 232, 238, 241, 247, 248, 253-250, 271, 272, 275; 283; morganic, 18, 21-23; four great complexes of, 18, 255 life, IQ, 21-23, 82, gl, 98, 99, 105, 110, 147, 115450232) 0253, 0044em2 53, 254 mega lifeless, 110; living, 145; physical, 98, 107, 145, 154,%150,¥233, 244025998294 278; physicochemical, 147, 160, 232, 254; primordial, 24-42 Enzymes, 15, 42, 57, 59, 69, 72, 73, 87-89, 100," FIO, E507 24042007207 Eocene, 135, 200, 218,236, 241, 255:;0956, 258-261, 263, 264, 268, 260, 274 Eotitanops, 263 (Fig.), 264; borealis, 264 (Fig.); gregoryi, 265 Erosion, 26-28, 30, 32 Eryops, 178, 180, 182 (Fig.), 183 (Fig.), 186, 190 i Eucken, Rudolf, 8 Eudendrium, 113 Euglena, 113 Eumicrerpeton, 179 (Fig.) Eurasia, 255 Europe, 79, 82, 164-166, 180, 182, 183, 190, IOI, 194-196, 205; .206, 208, 200.8 2a3 DEC. 250 .2UL cs ea 7A Eurypterids, 121, 125, 132, 133 (Fig.), 137; 154, 166, 291; see Sea-scorpions Eusarcus, 133 (Fig.) Evolution, causes of, 10, 20, 137, 245-251, 253; law of, 10; modes of, 238-245, 251, 252; of action and reaction, 16, 17; of interaction, 16, 17; of life, 2, 3, 5, 11, 17, 19; of matter, lifeless and living, 3-7; INDEX of the earth, 3, 7; of the elements, 3; of the four complexes of energy, 18; of the germ, 21, 23, 282, 283; of the glands, 74, 75; of the psychic powers, 114, 273; of the stars, 3, 7; theories of, Darwinian, 114, 144-146; Lamarckian, xii, 78, 114, 143-146; tetrakinetic, 22, 147; tetra- plastic, 23, 147; uniformitarian, 2, 24, 67 Extinction, 167, 253, 270 F Faraday, Michael, 56 Fats, 58, 248, 280 Feathers, 227, 228° Ferns, 213; see Flora, fern Fins, 129, 155-157, 164, 167-160, 172 (Fig.), LUA el 7a, LOlyelOoy, 1008 200, 204,220, 230 (Fig.) Fire-flies, 113 Fischer, Alfred, ot Fishes, 131, 154, 155, 157, 160-176, 186, I90, 199, 209, 210, 231, 239, 246, 253, 260, 275, 292; bony, 174, 175, see Tele- osts; fringe-finned, 174, see Ganoids, fringe-finned; lung-, 167, 168, 170 (Fig.), 172, 174, 292, see Dipnoi; pro-, 152, 161, 162 Flagellates, 111-113; see Mastigophora Flood-plain, 189, 196, 197, 217-220, 262 Flora, coal, 181, 185; cycad-conifer, 181, 185; fern, 180, see Ferns; lycopod, 180 Fluorine, 33, 36, 54 HOOG MOO, OO, s1047 111, 112,.1TA, TI§; 120, 136, 205, 239, 238-240, 250, 253, 254, 257, 287; adaptations, carnivorous, 143, 186, 188-192, 194, 238, 285; herbivorous, 143, IQO-192, 211, 214, 238, 260, 285; insectivorous, 186, 192, 194, 235, 237, 238; omnivorous, I9I, 285 Foot, 149, 159, 172 (Fig.), 182-184, 186, 100,.212—214,/ 220, 230,238, 240 Foraminifera, 32 (Fig.), 33, 50, 103, II5 (Fig.), 137, 290 Forests, 105; hardwood, 217 POM A, LOL. 7, Lo, 20-29) (815,02; 80; Q5, 107, 114, 137, 138, 142-145, 151, 152, ERY pe100, 050359105), 2315 °235,0240,-24.75 252,/25651200 Fox, 247 Fraas, Eberhard, 200 France, 217, 219, 263 Fresh-water, life, 35, 38, 42; plants, 63 oye Freundlich, 59 Fritsch (Fric), Anton, 177 Frog, 177) 178, 292 Function, 4,,10,-16}/19, 20, 46,°53, 55, 61, 62, 69, 79; 87, 107, 114, 115, 119, 142—- 145, 151, 154, 157, 160, 198, 231, 235, 239, 244-246, 252, 258, 280 Fungi, 67 G Galeopithecus, 239 Ganoids, 168-170 (Fig.), 175, 190, 2092; fringe-finned, 178, see Fishes, fringe- fined; lobe-finned, 168, 170, 292, see Crossopterygii Garpike, 168, 170, 292 Gaspé, 171 Gastropoda, 291; see Gastropods Gastropods, 120, 130; see Gastropoda Gastrostomus bairdi, 173 (Fig.), 174 (Fig.) Gaudry, Albert, 257 Gavials, 199, 211 Gegenbaur, Carl, 169, 172 Geikie, Archibald, 29 “General Sherman,” 96, 98 Geosaurus, 200 (Fig.), 210 Germ, 49, 144, 147, 150, 282, 283; see Cell; heredity-, 11, 19, 20, 280, 283; life-, 12 Germany, 172, 217 Gies, W. te; 32, 35; 38, 52, OF-03.; 72 Gigantactis ranhoeffent, 173 (Fig.), 174 (Fig.) Gigantosaurus, 217, 219 Gigantura chuni, 173 (Fig.), 174 (Fig.) Gila monster, 187 Gills, 178 Giraffe, 248 (Fig.), 249, 279, 292 Glacial conditions, 185 Glacial Epoch, 254, 271 Glaciation, 135, 180, 270, 271 Glacier, 102 Glands, 74-77, 246, 251; see Internal Se- cretion; pineal, 75; reproductive, 283, 289}; SeX, 75 Globigerina, 32 (Fig.); bulloides, 115 (Fig.) Glossopteris, 180 Glucose, 287, 289 Glycogen, 58 Glyptodon, 148 (Fig.) Gneiss, 28 Gondwana, 125, 171, 180, 217 Gorganopsians, 190, 191 314 Gorilla, 239 Graham, Thomas, 68 Granite, 26, 30, 32 Graphite, 32, 47, 118, 153 Gravitation, see Energy of gravitation Gravity, 68; see Energy of gravitation Great Bahama Banks, go Great Britain, 217 Great Plains, 213, 262 Gregory, W. K., 149, 235 Grenville, 50, 100, 103, 104, 153 Greyson shales, 120 Growth, 16, 61, 75, 142, 144, 147 Gymnosperms, 108 Gymnotus, 174, 176 H Habitat, adaptations, 155-159, 257, am- bulatory, 216, burrowing, 120, 126, 128, climbing, 227, 239, 243, cursorial, 190, 212, 227, 220, 243, 259, 206, digging, 239, flying, 199, 226-230, 239, gravipor- tal, 259, 263, leaping, 239, parachute, 227, running, 239, saltatorial, 243, swim- ming, 127, 128, 142, 143;.161, 162, 187, 199, 230, 231, 260, volplaning, 239; ma- rine, 195, 198, 200-202, 205, 260; zones, 152, 157-159, 179, 199, 236, 238-241, 254; 257; aérial, 130, 131, 133, 156, 157; 194, 227, 239, aéro-arboreal, 239, aquatic, WO 107s 1L0Sa210; 2275230; 24.200 70. abyssal, 120, 131, 156, 173-175, 230, deep-sea, 120, 194, fluviatile, 131, 156, 194-196, 198-202, 239, 270, lacustrine, 150, littoralatrop131/1S0, 1028174160. 199-202, 239, 270, paludal, 201, palus- tral, 156, 179, 200, pelagic, 115, 119, 120, T2201 20,01 27a beet SO 200-2 102230; arboreal "130... 13111 50,6203 .922 708 220, 230, 235-239, 241, 243, 244, arboreo- terrestrial, 227, 236, 239, 243, fossorial, 126, 131, 156, 179, 230, terrestrial, 130- 133, 0136, 150; 3707 180-108,7 1042100; T05-204,0210,* 201,502 7,a2G, 930,82 20. 241, 243, 244, 258, 260, 270, terrestrio- aquatic, 194, 202, 239 Haeckel, Ernst, 152 Hair, 147, 290 Hale, George Ellery, 47 Halimeda, 103, 104 Halley, Edmund, 35 Hamilton, 134, 136, 138 INDEX Hand, 140, 150 (Fig.), 184, 215, 280, 251 Hartleb, R., 83 Head, 129, 183, 187, 190, 208, 209, 222-226, 252, 259, 279 Heart, 192 Heat, see Energy of heat Heliotropism, 52, 111, 113 Helium, 41 von Helmholtz, H. L. F., 12, 13, 53 Hemocyanine, 66 Hemoglobin, 67, 247 Henderson, Lawrence J., 9, 20, 70 Heraeus, 82 Herbivora, 263, 265, 266; see Food adapta- tions, herbivorous; Herbivore Herbivore, 263; see Food adaptations, herbivorous; Herbivora Heredity, 10, 16, 19, 63, 77, 78, 93, 94, 98, 146, 147, 239, 281, 282, 289; see Chro- matin, heredity-; Germ, heredity- Hertwig, Gunther, 94 Hertwig, Oskar, 94 Hertwig, Paula, 94 Hesperornis, 230 (Fig.) Himalayas, 255, 256, 274 Hipparion, 266, 267 (Fig.) Hippopotamus, 239, 292 Hitchcock, Edward, 210 Hoatzins, 227 Holoptychius, 170 (Fig.) Holothurian, 126, 127; see Holothuroidea, Sea-cucumbers Holothuroidea, 125, 291; see Holothurian, Sea-cucumbers Hoppe-Seyler, 51 Hormones, 5, 74, 77, 78, 106, 116, 150, 246, 280 | Horns, 149, 224, 260, 264 (Fig.), 265 Horse, 151, 159, 258 (Fig.), 260, 262, 263, 266-268 (Figs.), 292 Horseshoe crab, 124 (Fig.), 125, 132, 201 Hot springs, 102, 103 Howe, Marshall A., 67, 104, 105 von Huene, Friedrich, 221 Humidity, 135, 180, 258 Huntington, Ellsworth, 136 Hiippe, 82 Huronian, 50, 153 Hutton, James, 24 Huxley, Thomas, 28, 57, 72, 191, 194, 235, 237, 240, 241, 255, 274 Hvyenodon, 241 Hyatt, Alpheus, 108, 152 INDEX : Hydrocarbons, 71 Hydrogen, 9, 31, 33, 38-40, 46, 47, 49, 51- 55, 58, 59-61, 63, 66, 67, 70-72, 88, 97, 98, I00, IOI Hydroid, 113, 290 Hydrosphere, 26, 33, 34, 99 Hypohippus, 266, 267 (Fig.) I Ichthyornis, 230 Ichthyosauria, 201; see Ichthyosaurs Ichthyosaurs, 155 (Fig.), 172, 193-196, 200, 203-205 (Figs.), 207, 210, 213, 230, 239, 292; see Ichthyosauria Ictidopsis, 190 (Fig.) Iguanodontia, 221-223, 224; see Iguano- donts Iguanodonts, 197, 211, 221-223; see Igua- nodontia Immunity, 73, 74 India, 180 Indian Ocean, 201 Individual, 19, 20, 22, 23, 68, 69, 78, 92, 95, 97, 103, 144, 147, 154, 233, 238, 244, 249 Individuality, 113, 148 Inhibition, 65, 66, 74 Inorganic, compounds, 107, 143; environ- ment, see Environment, inorganic Insecta, 133, 253, 291; see Insects Insectivore, 235-237, 239, 259, 292; see Food adaptations Insects, 130, 136, 181, 185, 254, 291; see Insecta; relation of plants to, 105 Interaction, 55 6, 15-23, 39, 53, 54, 56-58, 68, 69, 71-79, 80, 98, 106, 109, 116-118, 120, 142-145, 147, 150, 152, 154, 160, 231, 233, 242, 244-240, 251, 208, 271, 278, 280, 282, 283 Internal secretion, 74-79, 143, 160, 249- 251, 280, 282, 288, 289 Invertebrata, 118-140, 146, 153, 154, 253; see Invertebrates Invertebrates, 33, 50, 64-66, 75, 117, 118- 140, 153, 160, 231; see Invertebrata Iodine, 54, 66 Ionization, 39, 53-56, 63, 66; see Ions Ions, 14, 39; 54-56, 59; 61, 63, 67, 97, 117, see Ionization; negative, 54, 55, 06, 88, 176; positive, 54, 55, 88, 176 Iron, 32, 33, 46, 47, 50, 52, 54, 65, 66, 67, 68, 71, 82, 88, 90, 118, 153 Italy, 206 315 Jaekel, Otto, 217 James, William, 7 Jaws, IQO, 191, 214, 230, 245 Jellyfish, 126, 127, 129, 130 (Fig.), 290 Jennings, H. S., 113, 115-117 Johannsen, W., 147 Joly, 28, 36 Joule, James Prescott, 13 Jurassic, 135, 138, 153, 161, 168, 175, 178, 193-196, 198, 200, 205, 207, 210, 211, 213, 2122 Lge 222d 22 220 y 230 8250 K Kangaroo, 239, 243, 244, 292; tree, 203, 230, 243, 244 Kansas, 209 Kant, Emmanuel, 2 Karoo, 189 Keewatin, 50, 153 Kelvin, William Thomson, Lord, 14, 27, 49, a Keratin, 63, 153 Keweenawan, 50, 153 King, Clarence, 27 Kligler, Israel J., 87, 89, 91 Kohl, F. G., 92 Kolliker, A., 94 Kowalevsky, Woldemar, 257, 266 Krakatau, 285, 286 Kritosaur, 222; see Kritosaurus Kritosaurus, 223 (Fig.); see Kritosaur Krypton, 41 L Labidosaurus, 187 (Fig.) Labyrinthodont, 183 . Lacertilia, 193, 201, 231; see Lizards Lagoons, 184, 189, 196-198, 220, 262 de Lamarck, Jean Baptiste P. A. de Monet, 2NTAS, 157) 232, :240)-253,, 270 Lampreys, 168 Lamp-shells, 122, 123, 291; opoda, Brachiopods Lanarkia, 165 Lancelets, 162 (Fig.), 292; see Amphioxus Laplace, Pierre Simon, Marquis de, 25, 34, 286 de Lapparent, Albert A. C., 29 Laramide, 135, 136 see Brachi- 316 Lariosaurus, 206, 207 (Fig.) Laurentian, 50, 153 Lavoisier, Antoine Laurent, 2, 51, 286 Lead, 54 Leatherbacks, 202 (Fig.), 203 Leidy, Joseph, 196, 237 Lemur, 150, 236, 237, 239, 261, 274 Leopards, 225 Lepidosiren, 174 Lias, 50 Lichens, 32 Life, 2, 4-6, I1, 12, 15, 145, 281, 286, 288; bacterial stages of, 70, 80; dependent on temperature, 48-50; elements, 6, 33, 34, 37-39, 45-48, 53-56, 59-71, 82; energy concept of, 10-23, 281; environment, see Environment, life; first appearance of, 4; evolution of, 2, 3, 5, I1, 17, 10, 98, 99; latent, 48; orderly processes of, 116, 288; ‘origin of, 1, 2; 10, 20,:23,.35, 38, 41; 43, 49, 50, 58, 67, 80, 81, 145; primary stages of, 67-71; subject to chance, 7-9, 146; subject to law, 7-9, 146; theories of, creation, 5, entelechy, 10, 277, mate- rialistic, 3, 6, mechanistic, 2, 6, vitalism, 2, 10, $2, vitalistics 2, 6.50 Light, see Energy of light; production, 9, see Phosphorescence; ultra-violet, 60, 84; velocity of, 11 Limb bones, 168, 265, 266 Limbs, 155, 168, 172, 174, 178, 182-184, 186, 187, 190, 192, 197, 198, 200, 204, 206, 208, 1200, 0 2132-21002 19,5224 2 27220, 228-240, 252, 257, 205,206, 200, 270 Lime, 50, 91, 102, 120, 246 Limestone, 32, 65, 83, 85, 86, 90, 103,, 104, 118, 135, 137, 153 Limnoscelis, 187 Limulus, 125, 132; polyphemus, 124 (Fig.), 125 Lingula, 121; anatina, 122, 123 (Fig.) Lingulella, 121-123; acuminata, 121, 123 (Fig.) Linneus, 234 Lions, 225 Lists, see Tables Lithium, 54 Lithosphere, 26, 33, 34 Lithothamnium, 103 Lizards, 186, 188, 193, 194, 201, 231, 230, 292; see Lacertilia; half-, 206; sea, 209 (Fig.), 210 Lockyer, Sir Joseph Norman, 3 INDEX Locomotion, 17, I12, 115;#220,7131, 452; 154-157, 159, 165, 212, 224, 227, 229, 239 Loeb, Jacques, 42, 64, 66, 111 Loeb, Leo, 78 Loons, 230 ‘ Loricaria, 175 Louisella pedunculata, 126, 127 (Fig.) Lull Roa5.4.216,- 219 Lungs, 66, 178 Lyell, Charles, 24, 103, 254 Lysorophus, 1&1 M Macaques, 239 Mackenzia costalis, 126, 127 (Fig.) Madagascar, 150 Magnesium, 33, 36, 37, 46, 51, 54, 55, 63, 64, 65, 67, 68, 71, 82, 84, Lor Malayan Peninsula, 261 Mammalia, 190, 191, 234-274, 292; see Mammals Mammals, 23, 126, 131, 137; 142, 149, 155, ZOL5:163, 165).196-193, 195,200, 241,a4e 234-274, 275; see Mammalia; clawed, 236, 239; egg-laying, 236, 237, 292, see Monotremata, Monotremes; hoofed, 236, 237, 258, 259; pouched, 236, 237, 292, see Marsupialia, Marsupials; pro-, 192 Mammoth, woolly, 271 (Fig.), 273 Man, 46, 236-238, 269, 273 (Fig.), 274, 281 Manatees, 236, 237, 239, 269, 270 Manganese, 33, 52, 54, 71, 82, 88, 101 Manteoceras manteoceras, 264 (Fig.) Marine, habitat, see Habitat, marine; life, 37, 38, 42; organisms, 66; plants, 63 Marsh, Othniel C., 196, 216, 230, 237 Marsupialia, 237; see Mammals, pouched; Marsupials Marsupials, 203, 235, 236, 243, 292; see Mammals, pouched; Marsupialia Mastigophora, 112 (Fig.), 115, 290; see Flagellates Mastodons, 261, 264, 270, 273, 292 Matter, 1,4; 10,12; 18) 46, 51, 5éc08s. 760 95, 145; living, 64, 67, 286-288 Matthew, W. D., 235, 257 Mediterranean, 171, 188, 217, 260 Medusa, 126, 130 Melanostomias melanops, 173 (Fig.), 174 (Fig.) Merostomata, 121, 166; see Merostomes Merostomes, 124, 130; see Merostomata INDEX Mesohippus, 266 (Fig.) Mesosaurus, 207 (Fig.) Mesozoic, 135, 153, 161, 168, 178, 193, 194, 200, 206, 208, 236, 254, 255 Metazoa, 94; see Organisms, many-celled, multicellular Metchnikoff, E., 276 Meteorites, 30, 47, 49 Metopias, 183 Meuse, River, 209 Mexico, 206 von Meyer, Hermann, 177 Mice, 79, 271 Micrococcus, 85 Migration, 106, 114, 136, 154, 158, 180, 202, 205, 254, 255, 257, 261, 262 Minchin, E. A., 92 . Miner, Roy W., 120, 123 Miocene 2353236, 255,-256,\ 261, 267 Mississippi Sea, 134 Mississippian, 153, 161, 168, 178, 193, 227 Mites, 133, 291 Molaria, 125; spinifera, 124 (Fig.) Molecules, 39; 54-56, 58, 87, 97, 99, TOT, 117 Moles, 239 Mollusca, 90, 118, 131, 291; see Molluscs Molluscoida, 118, 291 Molluscs, 66, 130, 137; see Mollusca Monads, 17, 23, 46; see Bacteria Monkeys, 236, 237, 269, 274 Monodactylism, 159 Monotremata, 237; see Mammals, egg- laying; Monotremes Monotremes, 235, 236, 292; see Mammals, egg-laying; Monotremata Montana, 86, 102, 214, 222 Moodie, Roy L., 177, 180 Moon, 27, 29, 30 (Fig.), 44 Morgan, Lloyd, 244 Mormyrus, 176 Morrison, 218, 220; formation, 217; time, 219 Mosasauria, 201, 209; see Mosasaurs Mosasaurs, 186, 193, 195, 196, 200, 206, 208-210, 226, 239, 292; see Mosasauria Mosasaurus, 209 Motion, 160, 162, 184, 225; see Energy of motion; Newton’s laws of, 12, 13, 18, 22, 53 Moulton, F. R., 34 Mountain, formation, 134; revolution, 135 (Fig.), 256 (Fig.); upheaval, 136 317 Mountains, 181, 206, 255 Mount Stephen, B. C., 122 Miintz, A., 83 Muride, 271 ° Muscle, 10, 11, 162, 176, 289 Mutation, 63, 117, 138, 146; of de Vries, 106, 107, 140, 145, 268; of Waagen, 138-140 (Figs.) Mutationsrichtung, 138, 140, 242 N Nageli, C., 93 Naosaurus, 221 Nathanson, 83 Nautilus, 138, 291 Neck, 208, 209, 225, 248-250, 270, 279 Nemichthys scolopaceus, 173 (Fig.), 174 (Fig.) Neolenus serratus, 121 (Fig.) Neon, 41 Neoscopelus macrolepidotus, 173 (Fig.), 174 (Fig.) Nereis virens, 128 (Fig.) Nerves, 63, 176 Nervous system, 106, 107, 143, 184, 232, 280 Neumayr, M., 242 Nevada, 205 Newark time, 210-212 New Brunswick, 171 Newcomb, Simon, 141 New Guinea, 237, 273 New Jersey, 222 New Zealand, 208 Newland limestone, 85, 86 Newlandia concentrica, 102 (Fig.); N. fron- dosa, to2 (Fig.) Newt, 178, 292 Newton, Sir Isaac, 2, 12-14, 18,. 22, 53 Nickel, 54 Nile, 269 Niton, 41 Nitrate, 38, 45, 54, 62, 68, 82, 83, 86, ot, 105, 285 Nitrite, 38, 68, 82, 84, 86 Nitrobacter, 82, 83, 86 Nitrogen, 31, 33, 37, 38, 40, 41, 46, 47, 51, 545 58, 62, 63, 67, 68, 79; 81-88, OI, 99; IOI, 104, 105, 286 Nitroso coccus, 85, 86; N. monas, 82, 86 Noctiluca, 116 North America, 134, 136, 148, 164, 175, 180, 183, 184, 189, 191. 194-196, 198, 203, 205, 318 206, 208, 210, 212, 217, 219, 237, 255, 250, 2509, 261-263, 266, 270, 274 Nostocacee, 286 Nothosaurs, 201, 239 Nuclein, 92, 95 Nucleoproteins, 116 Nutrition, 16, 143, 280, 289 O Ocean, 4, 27, 38, 41, 80, 134; age of, 35, 36; salt-in the, 20, 35-37 Oceanic, basins, 25, 26, 118; invasion, 135, 136 OffenSess 17. 9020,00 21,2152; .100, 41050224, 225, 240.202 Ohio, 166, 167, 177 Okapi, 248 (Fig.), 268 Old Red Sandstone, 170 Olenellus, 121 Oligocene, 135, 236, 255, 256, 261-264, 266, 267, 209, 274 Olive, E. W., 92 Ontogeny, 108, 149 Ooze, 32 (Fig.); calcareous, 198; siliceous, 104 Ophiacodon, 186 Ophidia, 193, 201, 231; see Snakes Opisthoprocius solcatus, 173 (Fig.), 174 (Fig.) Opossum, 235 (Fig.), 236, 237, 243, 292 Ordovician, 50, 122, 123, 134, 135, 153, 160- 1O2,6105, 10O"070O.01035°250 Organic, compounds, 56, 58, 60, 67, 69-71, 101; deposits, 32, 33 Organism, 14-23, 39, 53; 56-59, 68-72, 78, 97, 99, 114, 145, 152, 238, 241, 246, 281- 283, 286; many-celled, 69, 110, 117, 245, see Metazoa; multicellular, 91, 94, 90, 103, 116, see Metazoa; single-celled, 60, TiO; -If2, 117, 118) 245, .see Protozoa; unicellular, 91, 94, 102, 110, II5, see Protozoa Ornithischia, 210, 221, 224 Ornitholestes, 213 Ornithomimus, 213-215 Orohippus, 258 (Fig.) Osteolepis, 170 (Fig.) Ostracodermata, 292; see Ostracoderms Ostracoderms, 154, 161, 164-170 (Fig.); see Ostracodermata Ostriches, 229, 230, 292 Otters, 239 INDEX Owen, Richard, 177, 189, 196, 237 Oxidation, 53, 60, 61, 90, QI, 100, 280 Oxygen, 9, 33, 37-42, 46, 47, 51-56, 61, 62, 63, 66, 67, 7°, 71, 82, 86-91, gg, 1ol Oxyhemoglobin, 66, 79, 247 Ve Pacific, 122; Coast, 206, 213; Coast Range, 136; see Coast Range Paddle, 172 (Fig.), 187, 200, 204, 206-209, 230 Paleaspis, 165 (Fig.) Paleocene, 236, 259, 261 Paleomastodon, 269 (Fig.), 270 Paleozoic, 28, 29, 34, 50, 104, 120, 135, 153, $00; 101; 168) 175,°178,21615.10%, 42008 236, 254, 255; post-, 28; pre-, 28, 29; 85 Palisade, 256 Palm, sago, 108 Palmyra aurifera, 129 Pancreas, 76, 289 Pantolambda, 259 (Fig.) Pantylus, 187 Paradoxides, 125 Parasitic, bacteria, 89; plants, 105 Parasuchia, 201 Parathyroid, 75, 250, 289 Pareiasauria, 185, 191; see Pareiasaurs Pareiasaurs, I90, 191; see Pareiasauria Paris, 255 Pasteur, Louis, 89 Patagonia, 219 Patriocetis, 241 Patten, William, 154 Pelagothuria natatrix, 127 (Fig.) Pelvis;210s221,.223 Pelycosaur, 186, 193 Pelycypoda, 291; see Pelycypods Pelycypods, 130; see Pelycypoda Penguin, 230 (Fig.) Pennsylvania, 176, 177, 180 Pennsylvanian, 153, 161, 168, 178, 193, 211, 227 Pentacta frondosa, 126, 127 (Fig.) Permian, 122, 135, 153, 161, 168, 178-186, 188-191, 193, 194, 198, 207, 210-212, 226, 227, 236, 237, 255, 256; reptiles, 201 Permo-Carboniferous, 182, 186, 187, 190, 210 Permo-Triassic, 135, 189 Peytoia nathorsti, 129, 130 (Fig.) Phalanger, 239, 243 INDEX Pheasant, 228 (Fig.) Phillips, John, 28, 209, 53 Phillips, O. P., 92 Phosphate, 65, 71, 120, 246, 285; calcium, 153 Phosphorescence, 14, 56, 113; see Light production Phosphorescent organs, 173-176 Phosphorus, 32, 33, 37, 47, 51, 54, 55 58, 63, 67, 68, 82, 88, 95, IOI, 104 Photosynthesis, 51 Phyllopods, 121, 125 Phylogeny, 108, 149 Physicochemical, changes, 74; energy, 20, 22, 48, 58, 95, 99, 150; environment, 147, 160, 232, 254; forces, 52; laws, 14; na- ture of life, 2, 5, 6, 15; processes, 14, 18 Phytosaurs, I9I, 193, 199, 211, 227 Pigeon, 228 (Fig.) Pine, 108 Pituitary body, 75, 249-251, 289, 290 Placentalia, 237; see Placentals Placentals, 236, 292; see Placentalia Placochelys, 203 (Fig.) Placodontia, 203 Planetesimal theory, 25, 26, 34 Plankton, ot Plants, 23, 32, 33, 41, 51-53, 55, 56, 63, 66, 67, 69, 79; 80, 87, OI, 99, 100, 105—1090, STO ste DetOO C21 7.1257 .0205 Platecar pus, 210 Plateosaurus, 216 (Fig.), 217 Pleistocene, 135, 210, 236, 238, 255, 261 Plesiosaur, 193-196, 200, 201, 206-208, 2092 Phocene; 135, 236, 256, 261; 263, 266, 274 Podokesaurus, 211 (Fig.) Poisons, 73, 116; see Toxic action Polycheta, 128 Polynoé squamata, 128 (Fig.), 129 Pools, 38, 84, 102, 180, 184, 189, 197, 198 Porcupine, 224 Porifera, 118, 131, 290 Porpoise, 155 (Fig.), 200 Portheus, 209 (Fig.), 210 Potassium, 33, 36, 37, 47, 52, 54, 55, 93, 64, 67, 68, 71, 82, 84, Io Poulton, Edward B., 7, 28, 144 Predentata, 195, 221, 225 Primates, 236, 237, 261, 274, 292 Proboscidea, 261, 265, 269-273, 292; see Proboscidians Proboscidians, 262, 263, 266, 269-271; see Proboscidea Joy Proboscis, 270, 271 Procolophon, 191 Proganosaur, 193 Proganosauria, 201, 207 Proportion, 75, 142, 208, 238, 248-252, 265, 266, 268-270, 279, 282 Protein, 49, 55, 58, 62, 66, 68, 70, 73, 74, 87, 88, 89, 107, 247-249, 280, 288, 289 Protitanotherium emarginatum, 264 (Fig.) Protocetus, 241 Protochordates, 162, 246 Protoplasm, 21, 22, 40, 46, 58, 61, 65, 77, 85, 87, 91-95, 99, 106, I10, If4, 116, 232, 288; origin of, 37, 38 Protozoa, 38, 50, 89, 90, 94, 104, 110-118, TIO gt. t843)1 5745 200,025 45,254, 9200; see Organisms, single-celled, unicellular Psychic powers, 114 Pteranodon, 226 Pterichthys, 166, 170 (Fig.) Pterodactyl, 226 (Fig.) Pterosaur, 193, 194, 211, 226, 227, 239, 292 Ptyonius, 179 (Fig.) Pupin, Michael I., 12, 13 Pygmies, 273 (Fig.) Pyrenees, 83, 255, 256 Q Quaternary, 161, 168, 178, 193, 227, 236, 256 R Radioactive elements, 28, 56 Radioactivity, see Energy of radioactivity Radiolaria, 32, 115 (Fig.), 290 Radium, 6, 11, 28, 41, 54, 56, 95 Rangifer tarandus, 271 (Fig.) Rats, 271 Rays, 168, 169, 292 Reaction, see Action and reaction Reade, T. Mellard, 36 Red Sea, 102 Redwood, 94, 96, 97 Regeneration, 116, 198, 199 Reichert, Edward Tyson, 79, 169, 245, 247 Reindeer, 271 (Fig.) Reproduction, 17, 18, 20, 102, 103, 105, 116, 1523272 Reptiles, 131, 137, 142, 161, 163, 165, 168, 172, 178, 181, 275; 184-226, 231-233, 239, 246, 253, 260, 266; see Reptilia; flying, 226, 292; mammal-like, 190, 191, 236, 292; Permian, 201; pro-, 185 320 Reptilia, 178, 180, 184-226, 231-233, 236, 292; see Reptiles; pro-, 189, 196 Respiration, 16, 40, 53, 61, 72, 280, 289 Retardation, 16, 17, 108, 145, 149, 233, 252, 268, 270, 279, 280 Rheas, 230 Rhinoceros, 260, 263, 264, 292; woolly, 272 (Fig.) Rhinoceros tichorhinus, 272 (Fig.) Rhizopods, 114 Rhizostome, 129 Rhodophycez, 104 Rhyncocephalia, 193, 201 Rhytidodon, 199 (Fig.), 211 (Fig.) Richards, Herbert M., 53 Rocks, 83, 84; see Chalk, Coal, Gneiss, Granite, Graphite, Limestone, Sandstone, Schists, Shale; decomposition of, 83; igneous, 27, 31, 32, 30, 44, 153; sedimen- tary, 29, 36, 100, 118, 153; see Sedimen- tary deposits; stratified, 90; volcanic, 32 Rocky Mountains, 136, 198, 205, 213, 217, 218, 220; 255,250, 201, 262 Rodents, 236, 237, 239, 258, 259, 271, 272, 292 Rumford, Benjamin Thompson, Count, 13 Russell, Henry Norris, 44, 46 Russia, 191 Rutherford, Sir Ernest, 3, 11, 28, 56, 59, 97 Ss Sagitta, 120, 120; gardineri, 129 (Fig.) St. Hilaire, Geoffroy, 158, 215, 279 Salamander, 178 Salt,. see Ocean, salt in the; chloride Saltation, 63, 140, 252, 268, 277 Sandstone, 65, 189, 198 Saratoga Springs, 102 Saurischia, 210 Sauropoda, 195, 196, 211, 213, 216-221, 266 de Saussure, N. T., 51 Saxony, 177 Scales, 147, 1790, 227 Schafer, Sir Edward, 74 Schickchockian Mountains, 134 Schists, 83 Schizophycez, 286 Schleiden, M. J., 93 Schopenhauer, A., 8 Schuchert, Charles, 134, 136, 165, 171, 180, 255 Schwann, T., 93 Sodium INDEX Scorpion, 125, 132, 133, 136, 291; sea-, 132, 133 (Fig.), 137 SCOUAN 1706175 ek Scrope, G. Poulett, 24 Scymnognathus, 192 (Fig.) Scyphomeduse, 129 Sea-cucumbers, 125-127 (Fig.), 291; see Holothurian, Holothuroidea Seals, 123031237, 230 Seas, 35, 90, 102, 104, 118, 119, 122, 181 Sea-urchin, 94, 97, 291 Sea-water, 37, 38, 90, 104 Sedimentary deposits, 90; see Rocks, sedi- mentary Sedimentation, 28-30, 118 Sediments, 26-28, 31, 197 pecleya Hs G50 Selection, 20-22, 69, 99, 117, 137, 140, 143- 145,147, 188, 225, 232, 233, 240, 241, 244, ICO; 205u272- 270 Semon, R., 144 Semostome, 130 Sequoia, 96 (Fig.), 97, 142; sempervirens, 96, 97; washingtonia (gigantea), 96, 98 Seymouria, 187 (Fig.) Shaleg2),65; 100,120,122, 177" Iso. 100 Shark, 134, 155 (Fig.), 161, 167-170 (Figs.), 172, 204, 230, 292; acanthodian, 161, 167 (Fig.) Shell, 148, 202 Shell-fish, 136 Shore, 122, 197 Shrew, 234, 239; tree, 235 (Fig.), 236, 252 Shrimp, 124 (Fig.), 291 Sierra Nevada, 136, 218, 256 Sierran, 135, 136 Silica, 31, 32, 50, 68, 104 Siliceous, ooze, 104; skeleton, 115 Silicon, 33, 47, 54, 67 Silurian, 50, 122; 132,.133,°%35, 153, 549 TOI, 164-160, LOS, 177,1170,,103,8250 Sirenians, 269, 270 Skates, 169 Skeletal, structure, 185, 246; system, 280 Skeleton, 555 63-65, 75) 115, 153, 154, 203— 205, 220, 228, 230, 252, 259, 267; cartilag- inous, 167 Skin, 168, 187, 197, 289 Skull, 185-187, 190, 270, 279 Sloth, 239; tree, 279 Smith, G. Elliot, 235 Smith, Perrin, 137, 160 Snakes, 186, 193, 194, 200, 231, 292; see Ophidia; sea-, 201 INDEX Sodium, 33, 35-37, 46, 47, 54, 55, 66, 71, 82, 84; chloride, 29; see Salt Soils, 83-85 Solar, heat, 43-45, 48, 51, 53, see Sun, ‘heat of; spectrum, 44 (Fig.), 46 (Fig.), 47, 52, 64, 65 (Fig.), ror, 111, 113 (Fig.) Sollas, W. J., 29, 36 South Africa, 171, 180, 184, 185, 189, 191, 197, 207 South America, 125, 148, 180, 195, 196, 217, 227, 237, 255, 256, 261 South Dakota, 161, 218 Spadella cephaloptera, 129 Specialization, 137, 158, 159, 165, 167, 175, 192, 260 Spectrum, solar; see Solar, spectrum Speed, 153, 164, 221, 265, 266 Spencer, Herbert, 143, 232 Sphargide, 202 Sphargis, 202 (Fig.) Spiders, 133, 291; sea, 166 Spines, 129, 161, 182, 188, 222, 224 Spirifer mucronatus, 138, 140 (Fig.) Spitzbergen, 205 Sponges, 32, 130, 290 Spores, 49, 103, 105, III Springs, hot, 102, 103 Spruce, 108 Squamata, 186 Squirrels, 239 Starch, 52, 58, 107, 287 Starfishes, 136 (Fig.), 172, 201 Stars, 3, 7, 18, 47, 48, 59, 60, 62; evolution of, 3,7 Stauraspis stauracantha, 115 (Fig.) Stegocephalia, 178, 180, 186, 190, 292 Stegomus, 211 (Fig.) Stegosaurs, 223, 224 Stegosaurus, 224 Sternoptyx diaphana, 173 (Fig.), 174 (Fig.) Stimulation, 65, 66, 74 Strasburger, E., 94 Strontium, 33, 34, 54 Struthiomimus, 213-215 (Figs.), 229 Sturgeon, 168, 170, 292 Stiitzer, A., 83 Stylonurus excelsior, 133 (Fig.) Stylophthalmus paradoxus, 173 (Fig.), 174 (Fig.) Sudburian, 50, 153 Suess, Eduard, 34, 125, 171, 180, 255 Sugar, 52, 86, 107, 286, 287 Sulphur, 33, 37, 47, 50, 54, 58, 62, 63, 67, 68, 82, 83, 88, ror 321 Sun, 4, 18, 22, 43-48, 51-53, 60, 113; heat ‘ of, 43-45, 48, 49, 52; 56, 84, Ito, see Solar heat; -spots, 47, 61 Sunlight, 43-45, 49, 51-53, 56, 84, 99, 105 Suprarenals, 75, 289 Survival of the fittest, 20, 22 Switzerland, 263 Symbiosis, 87, 92 Symbiotic, adaptation, 158; relations, 89 Synapta girardit, 126, 127 (Fig.) Synthetic, enzymes, 89; functions, 61 7 Tables, Lists, and Charts: action, reaction, and interaction, 16, 280; adaptation, 143, animals, 118, 131, 237, 290; chemical elements, 33, 37, 41, 51, 54, (to face) 67, 88; chronology, 29, 36, 50, 153, 161, 168, 17091035, 105,/211s 227512 30; 250; Climatic changes, 135; four complexes of energy, 22,99, 154; habitat zones, 131, 201, 202, 239, 243; phylogenetic charts, 50, 161, LOSMI OMT 37 214.0 227,8230 ‘Raconlen 435.1250 Tadpole, 177 Tail, 129, 178, 182-184, 186, 187, 207, 212, 215 224 295;/250,.270 Tapirs, 260, 263, 292 Tasmania, 180 Teeth, 64, 148 (Fig.), 149 (Fig.), 151, 166, TOL, Loe. Lod tO, LO2, 2054200, 221,225, 229, 238, 240, 252, 257, 266, 271, 272, 270, 290 Teleosts, 168, 170, 173,175, 292; see Fishes, bony Temperature, 25; 26, 43, 44, 48, 107, 135, TOOT 7961022421302 27232, eet Ae dependent on, 48-50 . Terebratula, 122, 123 (Fig.) Tertiary, 153, 161, 168, 178, 193, 194, 198, 227, 231, 232, 230, 254-259, 203, 274 Testudinata, 193, 231 Tethys, 171, 188, 217 Tetons, 104 Texas, 180, 183, 185, 187-189, 191, 198 Theriodont, r91 Thermodynamics, 5, 12-14, 18, 22, 53, I17 Therocephalians, 190 Theropleura, 186 Theropoda, 195 Thinopus, 175; antiquus, 176 (Fig.), 177 Thymus, 75, 289 322 Thyroid, 66, 75, 250, 289, 290 Tidal stability, 27 Tides, 35 Tigers, 225 Titanium, 33, 34, 47 Titanothere, 149, 258 (Fig.), 263-265 (Figs.), 270, 292 Toad, 178, 292 Tortoises, 193, 239, 292; sea, 201 Toxic action, 67 Trachodon, 197 (Fig.), 222, 223 (Fig.), 276; annectens, 222 (Fig.) Traquair, R. H., 170 Trematops, 182 Trias, 216, 217 EPTaSSIOALS Cy LS. LOTS LOO L 7 On ro350LG0— IQI, 193-200, 203, 205-207, 210-212, 216, DOA 220, 22742 20. 255-8250 Triceratops, 225 Tridactylism, 159 Trillium, 96 (Fig.), 97; sessile, 96 Trilobites,.120; 121 (igs) "1245-52561 30% 132,°T Aloe2O1 Trimerorachis, 182 Trinacromerion osborni, 208 (Fig.) Trinity-Morrison time, 218 Trituberculata, 236 Tuateras, 193, 194, 231, 292 Tupaia, 235 (Fig.) Turaco, 67 Turtles, 190, 193, 194; 200, 202, 205, 231, 239; sea, 202 (Fig.), 203 (Fig.), 206, 230, 292 Tusks, 259, 260, 270 Tylosaurus, 200 (Fig.), 209 (Fig.), 210 Tyrannosaurus, 215, 224 (Fig.); rex, 214 (Fig.), 225; see Frontispiece U Uintathere, 258 (Fig.) United States, 180, 270 Uranium, 28 Vi Varanops, 186 (Fig.) Varanus, 186 Variation, 8, 117, 140, 145, 147, 245 Velocity, 14,97; of character, see Character velocity; of light, 11 Vertebre, 188, 189, 252, 270, 276 INDEX Vertebrata, 131, TAt0r46, 18459253. 02024 see Vertebrates Vertebrates, 50, 75, 109, 117, 130, 138, 160, 168, 170, 175, 198, 218; see Vertebrata Viviparity, 204, 205 Volcanic, action, 29-31, 206; ash, 198; emanations, 68; heat, 45; islands, 213 Volcanoes, 40, 62, 134, I7I de Vries, Hugo, 7, 106, 107, 140, 144, 145 WwW Waagen, Wilhelm, 138-140, 276 Walcott, Charles D., 28, 29, 85, 118, 120, 122, 126,,120, 1600 Wallace, Alfred Russel, 24, 257 Walrus, 239 Wasteneys, Hardolph, 111 Water, 9; 18, 22, 28, 33, 34739; 49, 41, 45, 52, 55; 64, 68, 79; 83, 84, OI, 105, 106, 156, 285 Watson, D. M. S., 189 Weismann, AG) IQ, 20, 94, 95; 144, 145 Whales, 142, 200, 205, 234 (Fig.), 236, 237, 239, 241, 247, 252, 259, 260 (Fig.), 269, 292 Wheeler, W. C., 103 Williston, S. W., 180, 186, 209 Wilson, Edmund B., 92, 97 Wing, 199, 226-230 (Figs.) Winogradsky, S., 82 Wolf, 247 Wolves, 225 Woodward, A. Smith, 164 Worms, 128, 136, 291; see Annulata Worthenella cambria, 128 (Fig.) Wiirtemberg, 183 Wyoming, 161, 197, 205, 217, 220, 221 xX Xenon, 41 ac Yapok, 239 VY GASt 42727207 Yellowstone Park, 103 Z Zeuglodon, 200, 241, 242; cetoides, 260 (Fig.) Zeuglodons, 269 Zinc, 54, 56 Zymase, 42 1 eat Pa rr es ney cia ois isl ah Trae pa te ae A cave te DATE DUE 3 : 53 | ee h es < i c PRINTEDINU.S.A. 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