SS ae | ii amma | Marine Biological Laboratory Library Woods Hole, Mass. Presented by Dr. Roberts Rugh Jan., 1963 5S po SS SS | sf | SS SS Se ee ee ea Seen 0 0301 0011343 7 ROBERTS RUGH BIOLOGY DEPARTMENT WASHINGTON SQUARE COLLEGE NEW YORK UNIVERSITY Pet ig 1) ny ae ue D ioe : “ry DT gs 4 7 Spal”) sy rae Our Face rrom Fisn to Man. 1. Devonian shark; 2. Upper Devonian air-breathing, lobe-finned _ fish; 3. Lower Carboniferous amphibian; 4. Permo-Carboniferous reptile; 5. Triassic mammal-like reptile; 6. Cretaceous mammal; 7. Lemuroid primate; 8. Recent Old World monkey; 9. Chimpanzee; 10. Tasmanian; 11. Roman athlete. For details see p. xiii. OUR FACE FROM FISH TO MAN cA ‘Portrait Gallery of Our Ancient “Ancestors and Kinsfolk together with a (Concise History of Our Best Geatures BY WILLIAM K. GREGORY Professor of Vertebrate Paleontology, Columbia University; Associate in Anthropology and Curator of the Depart- ments of Ichthyology and Comparative Anatomy, American Museum of Natural History; Member of the National Academy of Sciences, etc. WITH A FOREWORD BY WILLIAM BEEBE With x10 Illustrations — ABCA, ~ S| LiaRaRy | = | reg wre » 4 ~ MASS. AS NEW YORK : LONDON G. P. PUTNAM’S SONS Che Anickerbocker Press 1929 OUR FACE FROM FISH TO MAN N Copyright, 1929 by G. P. Putnam's Sons Made in the United States of America TO HENRY FAIRFIELD OSBORN FOREWORD BY WILLIAM BEEBE A FOREWORD to a volume such as the present one of Dr. Gregory’s is as superfluous as would be the retention of the third eye, the Cyclopean one, of our ancestors, in the center of our forehead today. No more wonderful subject for a volume could be imagined than the evolution of the human face, and no more competent author than William K. Gregory. The result seems to me eminently satisfactory. If the reader’s interest is real but cursory, let him do nothing but look at the illustrations. They will ensure a thousand percent interest to every walk along Fifth Avenue or Regent Street. If pressure of other interests permits only an hour’s perusal, or complete lack of natural history know- ledge requires facts to be strained through the mesh of popular language, read but the preface and the first few paragraphs of each chapter. Taken as a whole this is not a “popular”? book in lil FOREWORD the sense of a superficial one. The details of evolution of our eyes, ears, nostrils, mouth—these are too delicate, too intricate for words of one syllable. Yet to read and understand this volume requires no more concentrated attention than the remembrance of the highest diamond in the ninth trick, or to what Steel Preferred fell in the Autumn of 1914. I advise no Fundamentalist or Anti-Evolutionist to read it, for if he have no sense of humor he will not understand it, and if he have, his belief will be like Dunsany’s King who “was as though he never had been.” If with Bergson we believe that the origin of laughter was cruelty, then an S. P. C. to something should be formed to prevent the spec- tacle of a Fundamentalist’s face functioning with the third eyelid of a bird, the ear-point of a deer, the honorable scars of most ancient gills, and with his lip-lifting muscles in full action as he sneers at truth. A moment’s thought of these few char- acters presents a new viewpoint on what we are wont to call the “‘lower”’ animals, for if our third eyelid were more than a degenerate flap we, like an eagle, could look straight at the sun; if our ears could straighten and turn as once, the lives of iv FOREWORD pedestrians would be safer; if the ghosts of gills were still functional, drowning would be impos- sible, and if the fang-revealing sneer showed less degenerate canines, we might have a more physi- cally wholesome fear of cavilers against the doc- trine of Evolution. The impregnable array of facts gleaned through the centuries of man’s intellectual supremacy proves beyond all question the gradual rise toward human perfection of the various components of the face, and this confirms our precious organs of sense as most noble gateways of the human mind and soul. Kindness, gentleness, tactfulness, pa- tience, can flow out through only these channels. It is a worthy thing to have written a book about them; it is a fortunate chance to be able to read it. PREFACE AccorDING to popular standards of civilized peoples, men of one’s own race and tongue were 99 66 called “men,” “warriors,” “heroes,” but people 99 66 of other races were “barbarians,” “‘unholy ones,” “foreign devils.”” The founder of one’s own clan was often considered to be the son of a deity, while the barbarians were the descendants of monkeys or other wild animals. Or the first man was created perfect, in the image of God. One’s own family, of course, was fairly true to type but sin had played havoc with the features of other races. To believe all this was comforting to one’s own “face”? in a world where the inferiority complex occasionally haunted even kings. Imagine then the effect of telling one-hundred- percent Americans that they are not the descen- dants of the god-like Adam but are sons and daughters of Dryomthecus, or of some nearly allied genus of anthropoid apes that lived in the Miocene Vii PREFACE age,—and that before that they had long tails and ate grubs and beetles! If the reader is curious to know the worst he will find it in these pages. There even his own great- grandfather—a Jove-like patriarch with ample beard, piercing eyes and an aquiline nose—will be subjected to unsparing analysis. It will be shown how much the proud old gentleman was indebted to a long line of freebooting forbears that strug- gled for a precarious living in the sea, on muddy flats, on the uplands or in the trees—zeons before Adam delved or Eve span. In detail it will even be charged that the real founder of the family was not the powerful settler to whom the king gave a grant of land extending far back from the river, but a poor mud-sucking protochordate of pre-Silurian times; that when in some far-off dis- mal swamp a putrid prize was snatched by scaly forms, their facial masks already bore our eyes and nose and mouth. Accordingly this little book can hardly expect much popularity either in Tennessee, where the very idea of evolution is anathema, or in the metro- politan strongholds where pithecophobia is still prevalent and man’s complete superiority to the Vili PREFACE all too man-like apes is somewhat nervously stressed. Nor can the author hope for much favor from the public, that wants only results and is willing to spend a billion dollars annually on cosmetics and safety razors. For this book does not pretend to tell how to improve one’s face but only how and why one has one. At best then it can only hold a magic mirror up to proud man and bid him contemplate his own image—a composite of an infinitely receding series of faces,—human, prehuman, anthropoid, long- snouted, lizard-like,—stretching back into the shadows of endless time. t He A) ING i CONTENTS FOREWORD A ; i : A : i li PREFACE . 5 . . i : $ sioh LONE PART I. PORTRAIT GALLERY OF OUR ANCIENT RELATIVES AND ANCESTORS THE VALUE OF A FACE THE BEGINNINGS OF OUR FACE THE SHARK’S FACE AND OURS : : Pa THE MASK-FACE OF OUR GILLED ANCESTORS . 20 OUR ANCESTORS COME OUT OF THE WATER . raf WHAT WE OWE TO THE EARLY REPTILES : 32 THE ONE-PIECE JAW REPLACES THE COMPLEX 16 7 A . . : ¢ : : 36 OUR MASK-FACE BECOMES MOBILE f ; 40 OUR LONG-SNOUTED ANCESTORS CROWD OUT THE DINOSAURS : : : ‘ ' 45 BETTER FACES COME IN WITH LIFE IN THE TREE-TOPS. : ‘ ; 3 : 52 THE ALMOST HUMAN FACE APPEARS ’ ’ 64 AT LAST THE “PERFECT” FACE . ; a RO PART II. CONCISE HISTORY OF OUR BEST FEATURES Tue Bony FRAMEWORK OF THE GOD-LIKE Mask 83 FIsH-TRAPS AND Faces . . : ; : 92 xl CONTENTS THE FIRST MOUTHS THE BEGINNINGS OF TEETH THE PRIMARY JAWS THE RISE OF THE SECONDARY JAWS AND THEIR TEETH . . : . ° . ORIGIN OF THE MAMMALIAN PALATE EVOLUTION OF THE TONGUE AND RELATED STRUCTURES ORIGIN AND EVOLUTION OF THE HUMAN LIPS LATER STAGES IN THE HISTORY OF THE TEETH CONCLUSIONS History oF THE NOSE OpticaL PHOTOGRAPHY AND ITS RESULTS THE HUMAN EYES AS INSTRUMENTS OF PRECISION THE EYES OF INVERTEBRATES ORIGIN OF THE PAIRED EYES OF VERTEBRATES * ORIGIN OF THE HUMAN EYES CONCLUSIONS PRIMITIVE SOUND RECORDERS ANCIENT AND MopErRN PHysioGNoMy Tue Facer or THE FUTURE Looxine BackwaRD . LITERATURE CITED . - : - ; 4 INDEX * . . ° . . . . xii PAGE ILLUSTRATIONS PAGE Our Facr From Fish to Man . . Frontispiece 1. Devonian shark, Cladoselache; 2. Upper Devonian air-breathing, lobe-finned fish, Eusthenopteron; 3. Lower Carboniferous amphibian, Eogyrinus; 4. Permo-Carbon- iferous reptile, Seymouria; 5. Triassic mammal-like reptile, Ictidopsis; 6. Cretaceous mammal, Eodelphis; 7. Lemuroid primate, Propithecus; 8. Recent Old World monkey; 9. Chimpanzee; 10. Tasmanian; 11. Roman athlete. FIGURE 1—Tue First Moutus . : ; ’ : 5 A. Slipper animalcule (Paramecium) with gash- like mouth. B. Jellyfish (Tessera), a two-layered sac with primitive mouth. (Both after Parker and Haswell.) 2.—Two Earty STAGES IN THE EVOLUTION OF A Heap TURNS . facing 6 A. Flatworm (Planaria), showing head-and-tail differentiation, including the beginnings of a brain and of eyes. B. Sand-flea (Orchestia), showing the interrelations of eye, brain, mouth, leg-jaws and nerve cord. (Both after Parker and Haswell.) 3.—TueE RIsE OF THE VERTEBRATES IN GEOLOGIC TIMES : : 3 j : , ; 9 4.—SoME oF Our EARLIEST KNown KINSFOLK: Urrer SILURIAN AND DeEvoniIAN OsTRACO- DERMS : : : : 3 ah | A. Pterolepis. (After Kiaer.) B. Tremataspis. (After Rohon.) xi ILLUSTRATIONS FIGURE PAGE C. Tremataspis. (After Patten.) D. Pteraspis. (After Powrie and Lankester.) E. Cephalaspis. (Composite, mainly after Patten.) 5.—Tue Face or tHE Most Primitive Livine Snark, Chlamydoselachus anguineus . facing 12 (After Garman.) 6.—INSTRUMENTS OF PRECISION IN THE HEAD OF A SHark, Chlamydoselachus anguineus . aie (After Allis.) Lateral line canals black, bordered with white; nerves white; muscles streaked; cartilage stippled. 7,—CARTILAGINOUS SKELETON OF HEAD OF SHARK 17 Comprising braincase, primary upper and lower jaws and branchial arches. 8.—Jaw Muscuses or SHark (Chlamydoselachus) . 18 Showing the essential similarity of the jaw muscles to the constrictors of the branchial arches. (Com- posite drawing based on the data of Allis and Garman.) 9.—CROSS-SECTION OF THE SKULL OF A Fossin Gan- orp Fisu, SHOWING THE BONE CELLS (Osteo- lepis FROM THE DrvontiAN OF Russia) . facing 20 (After Pander.) 10.—THE WeEpGE-SHAPED BRAINCASE oF A FIsH, Actinc aS A TuHrRustT-BLock or FULCRUM FOR THE BACKBONE . ‘ ; ’ P 22 The surface bones of the left cheek region have been removed to show the base of the skull and the elements dependent from it on the right side. (Modified from a drawing of the skull of the Striped Bass by F. A. Lucas.) 11.—Tue Factau Armor AND JAws or A DEVONIAN Lose-FINNED GaNoip Fisu (Osteolepis) facing 22 (After Pander.) The skull seen from above. XIV ILLUSTRATIONS FIGURE PAGE 12.—First CLAIMANT TO THE LINE or ANCESTRY OF THE HIGHER VERTEBRATES. DEVONIAN “LoBE-FIN” (Eusthenopteron) : . facing 23 (Reconstruction by Bryant.) 13.—SEcoND CLAIMANT TO THE LINE oF ANCESTRY OF THE HIGHER VERTEBRATES. DEVONIAN D1p- NOAN (Dipterus) ; : : . facing 24 (Restoration by Pander.) 14.—Empryos oF Moprern Lose-Finnep Fisu (A) AND AMPHIBIAN (B) . , e ‘ LOT 6 A. Embryo of Polypterus bichir. (After Budgett.) B. Embryo of Amblystoma punctatum. (After S. F. Clarke.) 15.—OneE or THE Most Primitive KNown AmpuHIB- IANS (Hogyrinus) FROM THE LoweER CaRrBon- IFEROUS OF ENGLAND , 28 Restoration of skeleton. (Based on data of D. M.S. Watson.) 16.—SKULL oF ONE oF THE OLDEST KNown AmpPHIB- IANS (Loxomma allmani) . : . facing 28 (After Embleton and Atthey.) A. Upper surface. B. Under side. 17.—SkuLLs oF LOBE-FINNED FisH anpD EARLY AMPHIBIAN, SHOWING Loss or OPERCULAR SERIES IN THE LATTER ; : hoe A. Lobe-finned fish, essentially Rhizodopsis. (From data by Traquair and Watson.) B. Primitive amphibian, Paleogyrinus. (After Watson.) In the primitive amphibians the space formerly covered by the opercular region was covered by the tympanum or drum membrane. XV ILLUSTRATIONS FIGURE 18.—CROSS-SECTION OF LABYRINTHODONT TEETH PAGE following 30 A. Lobe-finned Devonian fish (Polyplocodus). (After Pander.) B. Primitive amphibian of Carboniferous age (Loxomma allmani). (After Embleton and Atthey.) 19.—Two CriticaL STAGES IN THE Earty Evo.wv- TION OF THE SKULL A. Generalized reptile (Seymouria), retaining the full complement of amphibian skull elements. The temporal region, covering the upper jaw muscles, is still covered with a shell of bone as in primitive am- phibians and fishes. The otic notch (where the tym- panum, or drum membrane, was attached) is retained. (After data of Broili, Watson, Williston.) B. Primitive theromorph reptile (Mycterosaurus) with reduced number of skull elements and perforated temporal roof. The otic notch has disappeared. (After Williston.) 20.—SKULLS oF EARLIER AND Later MaAmMAL- LIKE REPTILES FROM SoutTH AFRICA A. Scymnognathus, a primitive, more reptile-like member of the therapsid series. B. Ictidopsis, a more advanced mammal-like mem- ber of the same series. Specimens in the American Museum of Natural History, with data from Broom, Watson, Haughton. 21.—PROGRESSIVE UpGROWTH OF THE DENTARY BonE oF THE LoweEeR JAw TO Form A NEW JOINT WITH THE SKULL A. Primitive mammal-like reptile (Scymnognathus). B. Advanced mammal-like reptile (Ictidopsis). C. Primitive mammal (Thylacinus). 22.—ORIGIN OF THE INTERARTICULAR Disc, OR Meniscus, Lyrnc BrtTwrEEN THE LOWER Jaw AnD Irs SocKET IN THE SKULL (After Gaupp.) XVi 33 35 37 38 ILLUSTRATIONS FIGURE PAGE 23.—ORIGIN OF THE FactaL Muscues or Man .. 42 A. Primitive reptile (Zabidosaurus) with continu- ous bony mask covering skull. (After Williston.) The mask was covered with thick skin without muscles, as in the alligator. B. Modern reptile (Sphenodon) with an open or fen- estrated skull covered with thick, non-muscular skin. The seventh nerve (heavy black line) is seen beneath the sphincter colli muscle, a broad band around the throat. (From Fiirbringer, modified from Ruge.) C. Primitive mammal (Echidna) in which the sphincter colli system has grown forward over the face. (After Ruge.) D. Gorilla. E. Man. (Both after Ruge.) 24.—DIAGRAM SHOWING THE CHIEF BRANCHES OF THE FactaL NERVE . 3 , : ‘ 44 A. Gorilla. (After Ruge.) B. Man. (After Weisse.) 25.—SuccESSIVE DOMINANCE OF THE AMPHIBIANS, Reptites, MamMMaAts AND Birps, Man sit a 26.—Tue Common Opossum, A “Livine Foss.” FROM THE AGE oF DINOSAURS . . facing 46 27.—SKULL Parts oF Extinct Opossum (Kodelphis) FROM THE Upper CRETACEOUS OF MONTANA 48 Superposed on outlines of skull of recent opossum. 28.—SKuLLs or (A) ADVANCED MAMMAL-LIKE ReEp- TILE (Ictidopsis) FROM THE TRIASSIC OF South AMERICA AND OF (B) a Mopern OpossuM . ; : , : . 49 29.—LONG-SNOUTED RELATIVES OF OURS FROM THE CreEetTACEOUS OF MONGOLIA ! : 50 A. Skull of Deltatheridium pretrituberculare. Nat- ural size. XVii ILLUSTRATIONS FIGURE PAGE B. Restoration of same. C. Skull of Zalambdalestes lechei. Natural size. D. Restoration of same. (All after Gregory and Simpson.) 30.—TuHE PEN-TAILED TREE-SHREW OF BorNEo facing 52 A “‘living fossil” representing a little-modified sur- vivor of the Cretaceous ancestors of the Primates. (Based on photographs and data given by Le Gros Clark.) 31.—TuHE SprectRAL TarsIER OF BorNEO ._ facing 53 A highly specialized modern survivor of a diversified group of primates that lived in the Lower Eocene epoch over fifty million years ago. (Drawn from specimen preserved in formalin, with aid of data from photo- graph of a living Tarsius by H. C. Raven.) 32.—SKELETON OF A PRIMITIVE FossiL PRIMATE (Notharctus osborni), FROM THE EOCENE OF WYOMING . : : : : . facing 54 33.—SKULL OF A PRIMITIVE PRIMATE OF THE Eocene Epocu (Notharctus osbornt) . «6 Natural size. (After Gregory.) 34.—ASCENDING GRADES OF FaAcES IN THE LOWER PRIMATES . : , : . facing 56 A. Lemur (Lemur variegatus) with fox-like muzzle and laterally-placed eyes. (After Elliot.) B. South American Monkey (Cebus capucinus) with shortened muzzle and widely separated nostrils. (After Elliot.) C. Old World Monkey (Lasiopyga pygerythrus) with nostrils approximated and forwardly-directed eyes. (After Elliot.) 35.—Tor View of THE SKULL IN REPRESENTATIVES or Srx Famiuies or PRIMATES, SHOWING THE More Forwarp DireEcTION OF THE ORBITS IN THE HicHErR Forms ; : : . 68 XViil FIGURE ILLUSTRATIONS Fossil lemuroid (Notharctus). Eocene epoch. African lemur (Arctocebus). Tarsius spectrum, Borneo. Marmoset (Midas). Gibbon (Hylobates). Chimpanzee (Anthropopithecus). 7AHO Of PS 36.—Si1pE VIEW OF SKULLS OF PRIMATES, SHOWING PROGRESSIVE SHORTENING OF THE Muzz.xp, DownwarRpD BENDING OF THE SUBORBITAL Face AND Forwarp GrRowTH OF THE CHIN A. Eocene lemuroid (Notharctus). B. Old World Monkey (Lasiopyga kolbi). (After Elliot.) C. Female chimpanzee. (After Elliot.) D. Man. 37.—EPpITOME OF THE FossiL History or HumMANn AND PREHUMAN PRIMATES. 1927 Showing the range in geologic time of the different groups, their dental formule, the side view of the tooth-bearing part of the lower jaw, the lower dental arch seen from above, and the back part of the lower jaw. A. Tree-shrews, represented by jaw of Leipsano- lestes siegfriedti, (After Simpson. Back part of jaw from modern tree-shrew Piilocercus). B. Primitive lemuroid, represented by jaw of Pelycodus trigonodus. (After Matthew.) C. Proto-anthropoid, represented by jaw of Parapi- thecus fraast. (After stereoscopic photograph by J. H. McGregor.) D. Proto-anthropoid, represented by jaw of Prop- liopithecus heckeli. (After stereoscopic photograph by J. H. McGregor.) E. Man-like anthropoid, represented by jaw of Sivapithecus himalayensis. (After Pilgrim.) F. Dawn-man, represented by jaw of Eoanthropus dawsoni. (After A. S. Woodward.) x1xX PAGE 59 61 ILLUSTRATIONS FIGURE PAGE G. Primitive man, represented by jaw of Homo heidelbergensis. (After Schoetensack.) H. Modern man, represented by jaw of Homo sapiens. (After Gregory.) 38.—EPpIToME OF THE FossiL History or HUMAN AND PREHUMAN PRIMATES (continued) : > Ge A. Primitive tree-shrew, represented by a left lower molar of Leipsanolestes. B. Primitive tree-shrew, represented by left upper molar of Indrodon. C. Primitive lemuroid, represented by left lower molar of Pelycodus. (After Matthew.) D. Primitive lemuroid, represented by left upper molar of Pelycodus. (After Matthew.) E. Proto-anthropoid, represented by left lower molar of Parapithecus. (From stereoscopic photo- graph by J. H. McGregor.) F. Proto-anthropoid, represented by left lower molar of Propliopithecus. (From stereoscopic photo- graph by J. H. McGregor.) G. Proto-anthropoid. Attempted restoration of upper molar to fit known lower molar. H. Anthropoid, represented by left lower molar of Dryopithecus rhenanus. (From stereoscopic photo- graph by J. H. McGregor.) I. Anthropoid, represented by left upper molar of Dryopithecus rhenanus. (From _ stereoscopic photo- graph by J. H. McGregor.) J. Dawn-man, represented by left lower molar of Eoanthropus dawsoni. (From stereoscopic photograph by J. H. McGregor.) K. Neanderthal man (Homo _ neanderthalensis), represented by left lower molar of ‘‘Le Moustier.” (From stereoscopic photograph by J. H. McGregor.) L. Neanderthal man, represented by left upper molar of ‘“‘Le Moustier.”’ (From stereoscopic photo- graph by J. H. McGregor.) xX ILLUSTRATIONS FIGURE PAGE M. Modern man (Homo sapiens), represented by left lower molar. N. Modern man (Homo sapiens), represented by left upper molar. 39.— OnE or Ovr Nearest Livinc ReEwatTIves. FEMALE CHIMPANZEE AND YOUNG . facing 64 (After Yerkes, from a photograph taken for Mme. Rosalia Abreu.) The baby chimpanzee was born in Mme. Abreu’s private collection of living primates, at Quinta Palatine, Havana, Cuba. (From “‘ Almost Human.” Courtesy of the author and The Century Co.) 40.—Ma.e AND FEMALE CHIMPANZEES . . facing 65 (After J.A. Allen, from photographs by Herbert Lang.) 41.—Lert Lower CHEEK TEETH oF Fossit ANTHRO- porn (Dryopithecus, B) From INDIA AND Fossit Primitive Man (Eoanthropus, A) FRoM PiIttTpOoWN, ENGLAND . i : . facing 66 The lower molars of the Piltdown jaw, although much ground down by wear, show the pure “‘ Dryopi- thecus pattern” characteristic of recent and _ fossil apes. (A, from photograph by J. H. McGregor; B, after Gregory and Hellman.) 42.—Fossiu ANTHROPOID AND HuMAN SKULLS . 68 A. Australopithecus. A young extinct anthropoid, Bechuanaland, South Africa. (After Dart.) B. Eoanthropus, England. (After A. S. Woodward and J. H. McGregor.) C. Pithecanthropus erectus, Java. (After Dubois.) D. Neanderthal (La Chapelle-aux-Saints), Europe. (After Boule.) E. Talgai, Australia. (After Stewart A. Smith.) F. Rhodesian, South Africa. (After A. S. Wood- ward.) XXl ILLUSTRATIONS FIGURE PAGE G. Cro-Magnon. (After Verneau.) In the female and young skulls the brow ridges are less projecting or entirely lacking. 43.—ANTHROPOID AND HumMAN Sxuuuis. Top Virw 69 A. Chimpanzee. (After Boule.) B. Pithecanthropus. (After Dubois.) C. Neanderthal (La Chapelle-aux-Saints). (After Boule.) D. Cro-Magnon. (After Boule.) 44.—ANTHROPOID AND HUMAN SKULLS. FrRONTVIEW 70 (After Boule.) A. Chimpanzee. B. Neanderthal (La Chapelle-aux-Saints). C. Modern European. 45.—CoOMPARATIVE VIEWS OF SECTIONED LOWER JAWS : : ' : ; hae A. Dryopithecus. (After Gregory and Hellman.) B. Chimpanzee. C. Piltdown. (After A. S. Woodward.) D. Heidelberg. (After Schoetensack.) E. Ehringsdorf. (After Virchow.) F. Neanderthal (Le Moustier). (After Weinert.) G. Cro-Magnon. (After Verneau.) 46.—Tue “Autmost Human” SxKvuuu or Australopi- thecus, A YouNG Fosstzr AnTHROPOID . facing 72 (After Dart.) 47.—RESTORATION OF THE HEAD OF THE YOUNG Australopithecus : ; . facing 73 (After a drawing by Forrestier made under the direc- tion of Professor G. Elliot Smith.) 48.—EVOLUTION OF THE HUMAN SKULL: TEN StRUC- TURAL STAGES . : } : 78 I. Lobe-finned fish, Devonian age (essentially Rhizodopsis). (After Traquair, Watson, Bryant.) XXli FIGURE ILLUSTRATIONS PAGE II. Primitive amphibian (Pale@ogyrinus), Lower Carboniferous. (After Watson.) III. Primitive cotylosaurian reptile (Seymouria), Permo-Carboniferous. (After Broili, Williston, Watson.) IV. Primitive theromorph reptile (Mycterosaurus), Permo-Carboniferous. (After Williston.) V. Gorgonopsian reptile (Scymnognathus), Permian. (After Broom.) VI. Primitive cynodont reptile (Ictidopsis), Tri- assic. (After Broom, Haughton.) VII. Primitive marsupial (Eodelphis), Upper Creta- ceous. (After Matthew.) VIII. Primitive primate (Notharctus), Eocene. (After Gregory.) IX. Anthropoid (female chimpanzee), Recent. X. Man, Recent. 49.—EVOLUTION OF THE HUMAN SKULL-ROOF i 79 Same series as in Fig. 48, except that in No. VII the recent opossum instead of its fossil ancestor is used. Abbreviations: na, nasal; fr, frontal, pa, parietal; it, intertemporal; st, supratemporal; tab, tabular; dso, dermosupraoccipital. 50.—EvVoLUTION OF THE HUMAN JAWBONES . y 80 Same series as in Fig. 49. Abbreviations: pmz, premaxilla; mz, maxilla; dn, dentary. 51.—EVOLUTION OF THE CIRCUMORBITAL BONES . 81 Same series as in Fig. 49. Abbreviations: prf, prefrontal; la, lacrymal; ju, jugal (malar); po, postorbital. 52.—EVOLUTION OF THE Bones BEHIND THE JAWS (TEMPOROMANDIBULAR SERIES) . : Se Same series as in Fig. 49. Abbreviations: sg, squamosal (squamous portion of XXlil ILLUSTRATIONS FIGURE temporal); quj, quadratojugal; sur, surangular; an, angular; pospl, postsplenial; spl, splenial. Figures 48-52 give excellent examples of “‘ Williston’s law” of the progressive elimination of skull elements in passing from fish to man. 53.—EVOLUTION OF THE UNDER SIDE OF THE SKULL I. Lobe-finned fish (Eusthenopteron), Devonian. (After Bryant, Watson.) II. Primitive amphibian (Baphetes), Carboniferous. (After Watson.) III. Primitive cotylosaurian reptile (Seymouria), Permo-Carboniferous. (After Watson.) IV. Advanced cotylosaurian reptile (Captorhinus), Permo-Carboniferous. (Original.) V. Gorgonopsian reptile (Scymnognathus), Per- mian. (After Watson.) VI. Advanced mammal-like reptile (Cynognathus), Triassic. (Mainly after Watson.) ; VII. Marsupial mammal (Thylacinus), Recent. (Original.) VIII. Eocene lemuroid primate (Adapis). (After Stehlin.) IX. Anthropoid (female chimpanzee). (Original.) X. Man (Australian aboriginal). (Original.) Abbreviations: pmz, premaxilla; mz, maxilla; ju, jugal; quj, quadratojugal; qu, quadrate; nar, internal naris; pv, prevomer; pl, palatine; ectpt, ectopterygoid; epipt, epipterygoid; pt, pterygoid; pas, parasphenoid (= vomer, v); bs, basisphenoid; bo, basioccipital; exo, exocci- pital; ops, opisthotic; mst, mastoid portion of periotic; bul, auditory bulla; sg, squamosal; alsp, alisphenoid. 54.—ANATOMY OF THE LANCELET (Amphiorus), THE Most Primitive Living CHorDATE (PRE- VERTEBRATE) ANIMAL (After Delage and Hérouard.) A. Entire animal, seen as a semi-transparent object. B. Longitudinal section. XX1V PAGE 85 92 ILLUSTRATIONS FIGURE PAGE 55.—Larv& oF Ecurnoprerms (A, B) AND OF THE ““Acorn WormM” (Balanoglossus) . ; Oe A. Auricularia, larva of a sea-cucumber. B. Bipinnaria, larva of a starfish. C. Tornaria, larva of Balanoglossus. (A, B, C, after Delage and Hérouard.) 56.—INNER AND OvutTeR MoutsH PoucusEs In EMBryo VERTEBRATES . : : : ; . 94 A. Larval lamprey, longitudinal section of head. (After Minot.) Showing the nasal pit, hypophysis and mouth cavity arising as infolds from the ectoderm or outer cell-layer. B. Embryo rabbit, longitudinal section of head. (After Mihalcovics.) 57.—ATTEMPTED RESTORATIONS OF THE MoutH AND Gitt REeGIon oF Two CEPHALASPID OstRACO- DERMS BY STENSIO . : : : , 95 A. Horizontal section through the ventral part of the head of Kieraspis, showing the assumed position of the gill-sacks. The ducts (&. ebr.) leading from the gill-sacks are preserved in the original fossils, also the ridges (7 6 s) between the ducts, so that by comparison with the anatomy of recent lampreys there is no substantial doubt that the gill-sacks were placed as in the restora- tion. B. Underside of the head shield of Cephalaspis, showing the probable position of the gill openings (ebr. c ebr. c) and mouth (m). 58.—SwIiFrT-MoviING OstracopERM (Pterolepis nitidus) FROM THE SILURIAN OF Norway ; BY, 96 (After Kiaer.) 59.—A MoprerN DESCENDANT OF THE OSTRACODERMS 97 A. Adult lamprey. (After Jordan and Evermann.) B. Longitudinal section of larval lamprey, enlarged (After Goodrich.) XXV ILLUSTRATIONS FIGURE PAGE 60.—DEVELOPMENT OF TEETH IN LAMPREY AND SHARK , 2 ! ; : ; : 99 (After Goodrich.) Sections of developing tooth germs: A. lLamprey. B. Shark. First stage, showing tooth papilla beneath basal layer of epithelium. C. Shark. Second stage, showing secretion of the enamel layer. D. Shark. Advanced stage, showing lips of shagreen denticles breaking through the epithelium. 61.—EvoLuTION or THE JAw Muscues From Fisu to Man . , : ‘ : > We I. Shark (Chlamydoselache). (Data from Allis.) II. Lobe-finned ganoid (Polypterus). (After L. A. Adams.) IiI. Primitive amphibian (Eryops). Restoration. (After L. A. Adams.) IV. Primitive mammal-like reptile (Scymnognathus). Restoration. (Skull mainly from Broom.) V. Advanced mammal-like reptile (Cynognathus). Restoration. (After L. A. Adams.) VI. Primitive marsupial (Opossum). (After L. A. Adams.) VII. Primitive Eocene’ primate (Notharctus). Restoration. VIII. Chimpanzee. IX. Modern man. 62.—Meruops or ATTACHMENT OF THE PRIMARY Upper Jaw To THE UNDER SIDE OF THE SKULL 105 A. Hyostylic attachment (by means of the hyo- mandibular cartilage), characteristic of shark. (After Gegenbaur.) B. Autostylic attachment (by means of an epi- pterygoid process from the primary upper jaw). Car- XXV1 ILLUSTRATIONS FIGURE PAGE tilaginous braincase and primary upper jaw of fcetal salamander. (After Gaupp.) C. Skull of primitive fossil reptile (Diadectes) from the Permo-Carboniferous of Texas. In C the bony mask covering the temporal region is cut through and a part of it removed to show the primary upper jaw (comprising the palatine, pterygoid, epi- pterygoid and quadrate bones) and their relations to the braincase. 63.—UNDER SIDE OF THE SKULL OF (A) DEvonIAN Fosstt Fisn (LOoBE-FINNED), AIR-BREATHING Crossopt (Eusthenopteron) anp (B) Primt- TIVE Fossiz AMPHIBIAN (Baphetes). (A AFTER Bryant anD Watson; B arrer Watson) . 108 The secondary upper jaws (premaxille, maxillx) are on the margins; the primary upper jaws (palato- quadrates) are largely covered by tooth-bearing plates of the primary palate. 64.—Ricut Har or tHE Lower Jaw or Lose- FINNED Fossit Fiso (A, C), AND PRIMITIVE Fossi. AMPHIBIAN (B, D), ano Recent TurTLE Emsryo (E) : ‘ apes la A. Megalichthys, outer side. (After Watson.) B. Trimerorhachis, outer side. (After Williston.) C. Megalichthys, inner side. (After Watson.) D. Trimerorhachis, inner side. (After Williston.) E. Recent turtle embryo, inner side. (After Parker.) Abbreviations of names of bones: ang, angular; art, articular; cor, coronoids (I, II); dn, dentary; preart, prearticular; pospl, postsplenial; spl, splenial; swrang, surangular bone. In the embryo turtle Meckel’s cartilage is very plainly seen on the inner side of the jaw, extending the full length of the jaw. The rear end forms the articu- lar bone of the adult. These jaws are made mostly of the dermal sheathing bones that in the embryo surround the primary carti- XXVil ILLUSTRATIONS FIGURE PAGE laginous jaw. The only part of the primary jaw present in the adult is the articular bone. 65.—EarLy EMBRYONIC STAGES IN THE DEVELOP- MENT OF THE NosE IN Man ; ' . 120 (After Keith.) 66.—CoMPARATIVE ANATOMY OF THE HumMAN PauaTE 121 A. Recent shark, showing groove from nose to front of mouth. (After Keith.) B. Lizard, in which internal opening (choana) from the nose opens in the forepart of the mouth cavity. (After Plate, Allgem. Zool., Gustav Fischer.) C. Lion pup with cleft palate, recalling in form the palate of reptiles; showing internal opening of the nose (indicated by the arrow-point) in the forepart of the mouth cavity. In this abnormal specimen the second- ary palate has failed to grow over to the mid-line. (After Keith.) D. Human embryo of the end of the sixth week, showing the secondary palatal plates beginning to grow in toward the mid-line and the “primitive choanze”’ (arrow-point) still exposed in the forepart of the roof of the pharnyx. (After Keith.) 67.—LONGITUDINAL SECTION OF HEAD IN YOUNG Goritta (A) AND IN Man (B), SHOWING RELATION OF TONGUE TO SURROUNDING Parts 124 (After Klaatsch.) 68.—LONGITUDINAL SECTION OF LOowER JAW OF Monkey (A) AND Man (B), SHow1ne ATTACH- MENT OF THE TONGUE MUSCLE TO THE Back OF THE JAW. ; : ; , . a6 (After Robinson.) In B the subdivision of the tongue muscle into strands is over-emphasized in order to show how the upper surface of the tongue could be thrown into different contours by the contraction of different strands of the genioglossus muscle. XXVill ILLUSTRATIONS FIGURE C. Diagram of the genioglossus muscle in pro- nouncing the sound “‘oo.’”’ (After Robinson.) D. Diagram of the genioglossus muscle in pro- nouncing the letter “T.’’ (After Robinson.) 69.—HumMAN EMBRYO OF THE THIRD WEEK (From Eidmann, after His.) Oblique front view of the head, showing mouth, primary upper and lower jaw buds, gill arches and gill slits. (From Entw. d. Zaéhne. .., Hermann Meusser, Berlin.) 70.—OLp CHIMPANZEE, SHOWING EXTRAORDINARY PROTRUSION OF THE Lips IN ANTHROPOIDS PAGE 127 facing 132 (From J. A. Allen, from a photograph by Herbert Lang.) 71.—THREE STAGES IN THE DEVELOPMENT OF HUMAN TEETH : ; A. Future tooth-bearing skin still on the surface of the mouth cavity. From a human embryo eleven millimeters long. B. Beginnings of the tooth-pouch. From a human embryo sixteen millimeters long. (A, B, from Eidmann, after Ahrens. Entw. d.Zéhne..., Hermann Meusser, Berlin.) C. Beginnings of the pulp cavity. From a human embryo thirty-two and one-half millimeters long. (After Corning, Lehrb. d. Entw. des Menschen, J. F. Bergmann.) 72.—CENTRAL INcISORS OF GORILLA AND Man. ENLARGED : ‘ ' : A. Upper left incisor of young gorilla, palatal side, showing small mammille on incisal edge, basal swelling, raised marginal rims and low lingual ridges. B. Upper left incisor of fossil Neanderthal (Le Moustier), showing mammillate incisal edge, basal swelling and ridges. (After Weinert.) XX1X 135 137 FIGURE C, ILLUSTRATIONS PAGE Upper left incisor of fossil Neanderthal (Ehrings- dorf), showing basal swelling and ridges. (After Virchow.) Dp; Upper left incisor of old Egyptian, showing mammillate incisal edge, marginal rims and lingual ridges. (After Hrdlicka.) E. Lower right incisor of young gorilla, showing mammillate incisal edge and faint lingual ridges. F. Lower right incisor of Neanderthal (Le Moustier.) (After Virchow.) G. Lower right incisor (labial surface) of white boy, showing mammillate incisal edge and labial ridges. (From Hrdli¢ka, after Zuckerkandl.) 73.—Tue THREE Typses oF CENTRAL Upper Inctsors 139 (After J. Leon Williams.) Lower row, first type; middle row, second type; upper row, third type. 74.—PaLaTAL ARCHES OF ANTHROPOIDS AND Men . 140 A. D. E after F. after Gibbon, female. (From Selenka, after Rise.) Gorilla, male. (From Selenka, after Rise.) Chimpanzee, female. (From Selenka, after Rése.) Orang, female. (After Hrdliéka.) Neanderthal man (Le Moustier). (From Weinert, Dieck.) Modern white man, composite. (From Selenka, Rose.) 75.—LoweER Front PREMOLARS OF Fossit ANTHRO- POIDS AND MAN : é : , . 144 A. Fossil anthropoid, Dryopithecus fontani. (After Gregory and Hellman.) B. Fossil anthropoid, Dryopithecus cautleyi. (After Gregory and Hellman.) C. Fossil anthropoid, Sivapithecus himalayensis. (After Pilgrim.) D. Fossil Neanderthaloid (Ehringsdorf). (After Hans Virchow.) E. Homo sapiens. (After Selenka, from Rise.) Xxx FIGURE ILLUSTRATIONS 76.—MiLx TreetH or Man AnNp GORILLA A. White child. (From Selenka, after Rise.) B. Gorilla child. (From Selenka, after Rése.) 77.—TEN STRUCTURAL STAGES IN THE EVOLUTION OF THE Human DENTITION FROM ASCENDING GEOLOGICAL Horizons I. Substage a. Permo-Carboniferous. Myctero- saurus, primitive theromorph reptile. (After Williston.) Substage 6. Permian. Scylacosaurus, primitive mam- mal-like reptile. (After Broom.) Substage c. Tri- assic. Cynognathus, advanced mammal-like reptile. (After Seeley.) II. Triassic. Diademodon, advanced mammal-like reptile. (Mainly after Seeley. Occlusion diagram by author.) Ill. Jurassic. Pantotherian (primitive _pro- placental). (Kindness of Dr. G. G. Simpson. Occlu- sion diagram by Simpson.) IV. Cretaceous. Pre-Trituberculate, Deltatheridium. (From the original specimen. Occlusion diagram by author.) V. Lower Eocene. Primitive placental, Didel- phodus. (From the original specimen. Occlusion dia- gram by author.) 78.—TEN STRUCTURAL STAGES IN THE EvoLUTION or THE Human DENTITION (continued) VI. Middle Eocene. Primitive primate, Pronycti- cebus. (After Grandidier. Occlusion diagram by author.) VII. Upper Eocene. Advanced tarsioid primate, Microcherus. (After Stehlin. Occlusion diagram by author.) VIII. Miocene. Primitive anthropoid primate, Dryopithecus. (Upper molars mainly after Pilgrim; lower molars from type of Dryopithecus cautleyi. Occlu- sion diagram by author and Milo Hellman.) XXX1 PAGE 146 147 148 FIGURE ILLUSTRATIONS IX. Pleistocene. Primitive man, Mousterian. (From stereoscopic photographs by J. H. McGregor and from the published photographs by Weinert and by Virchow (m;). Occlusion diagram by author. X. Recent. Modern man, white. (From the original specimen. Occlusion diagram by author.) 79.—Tue Dryopithecus PaTTERN IN THE LOWER Moxuar TEETH OF RECENT AND FossiL ANTHROPOIDS (After Gregory and Hellman.) A. Fossil anthropoid (Dryopithecus fontani). The first lower molar shows the fovea anterior, the five main cusps and the fovea posterior. B. Fossil anthropoid (Dryopithecus cautleyi). The third lower molar (at the left) shows a perfect Dryopi- thecus pattern. C. Fossil anthropoid (Dryopithecus fricke). (Com- pare Fig. 80 C.) D. Recent orang-utan. The Dryopithecus pattern is somewhat obscured by the secondary wrinkles of the enamel. E. Recent chimpanzee. The Dryopithecus pattern in this particular specimen is slightly obscured by the secondary wrinkles of the enamel. Cusp 6, a bud from the hinder rim of the tooth is present in the second lower molar. (Compare Fig. 80D.) F. Recent gorilla. The teeth are elongated in a fore-and-aft direction and the cusps are high and nipple-like. 80.—ProGREsSIVE REDUCTION AND LOSS OF THE Dryopithecus PATTERN IN THE LowEeR Mo.uars oF Fossit AND Recent MEN. (After Gregory and Hellman.) A. Fossil Heidelberg man. Worn lower molar crowns, showing clear traces of the Dryopithecus pattern. XXXil PAGE 150 151 ILLUSTRATIONS FIGURE B. Fossil Ehringsdorf man. Both the first and the second lower molar clearly show the fovea anterior. (Compare Fig. 79A.) The second lower molar shows an early stage in the formation of the cruciform or plus pattern. C. Fossil Neanderthal man (Le Moustier), showing modified Dryopithecus pattern. Cusp 6, occasionally found in the anthropoids, is present. D. Recent Australian aboriginal. In the first molar the Dryopithecus pattern is very evident; the base of cusp 3 is in contact with the base of cusp 2; cusp 6 is unusually large. In the second lower molar the Dryopithecus pattern is changing into the plus pattern. E. Modern Hindu, showing Dryopithecus pattern in the first lower molar, and plus pattern in the second. F. Modern White, with modified Dryopithecus pat- tern in the first lower molar, a complete plus pattern in the four-cusped second molar, and a reduced third lower molar. 81.—DissecTION oF HEAD oF SHARK, SEEN FROM ABOVE, TO SHOW RELATIONS OF OLFACTORY CapsuLes TO Brain, Eyres AnD INTERNAL Ears é : : : (Modified from Marshall and Hurst.) 82.—JACOBSON’S ORGAN IN THE HumMAN Fartus A. Location of Jacobson’s organ. The sound is inserted into the opening of the organ. (After Corning.) B. Frontal section of foetal human nose, showing vestige of Jacobson’s organ. (After Corning.) (A, B, from Lehrb. d. Entw. des Menschen, J. F. Bergmann.) 83.—LONGITUDINAL SECTION OF THE SKULL IN MAn AND CHIMPANZEE A. Adult female chimpanzee. B. Man. (After Cunningham.) XXXIll PAGE 155 159 160 ILLUSTRATIONS FIGURE 84.—Broap, ForwarpLy-DirEcTED NosrE or HuMAN Farvus (A), (AFTER KOLLMANN) AND GORILLA Farvus (B), (FRoM SCHULTZ, AFTER DENIKER) 85.—CONNECTIONS OF THE FRONTAL, ETHMOID AND SpHENOID SINUSES WITH THE NasaL MEatTI (After Keith.) 86.—DEVELOPMENT OF THE Face IN Man (From Eidmann, Entw. d. Zaéhne..., Hermann Meus- ser, Berlin). A. Embryo of about 9 millimeters length. Eidmann, after His.) B. Embryo of about 10.5 millimeters length. Eidmann, after His.) C. Embryo of about 11.3 millimeters length. Eidmann, after Rabl.) D. Embryo of about 15 millimeters length. Eidmann, after Retzius.) E. Embryo of about 18 millimeters length. Eidmann, after Retzius.) (From (From (From (From (From 87.—DEVELOPMENT OF THE Face In MAN (continued) A. Late fetal stage: embryo of 52 millimeters length. (From Eidmann, after Retzius, Entw. d. Zdhne. . Hermann Meusser, Berlin.) B. Diagram of adult face, showing derivation of different areas from the primary embryonic parts. (Modified from Keith.) 88.—NASAL PROFILES AND RELATED Parts In Man (After Schultz.) A. Negro child. B. Negro adult. C. White child. D. White adult. Median or septal cartilage, black. XXX1V PAGE 161 163 165 166 168 ILLUSTRATIONS FIGURE PAGE Shows the correlation of the extent of the septal cartilage, the position of the front teeth and the form of the nose. 89.—ExTREMES OF Nose Form In Man . facing 170 A. Excessively wide short nose in African pygmy. (From Martin, after Czekanowski.) B. Excessively narrow high nose in a white man (Tyrolese). (From Martin, after Czekanowski.) C. Excessively high nose bridge and long nose in an Armenian. (After von Luschan.) D. Excessively low nose bridge in South African Bushman. (From Martin, after Schultz.) (A, B, D, from Lehrb. d. Anthropol., Gustav Fischer.) 90.—EXTREMES IN Face Form anp Cotor . facing 172 A. Hottentot woman. (From Martin, after Poech, Lehrb. d. Anthropol., Gustav Fischer.) B. Nordic Swede. (From Lundborg and Runnstrém, ““The Swedish Nation,” H. W. Tullberg.) 91.—TuHE BrGInniInGs or EYEs . 4 : LS A. Section of an ocellus, or eye spot, at the base of a tentacle of a jellyfish (Catablema). (From Plate, after Linko.) B. Section of a “‘goblet eye” of a jellyfish (Sarsia). (From Plate, after Linko.) (A, B, from Allgem. Zool., Gustav Fischer.) 92.—EyE CaApsuLES OF FLATWORM : » a CG A. Location of eyes in flatworm (Planaria). (After Parker and Haswell.) B. Section of “goblet eye”’ of flatworm (Planaria). (From Plate, after Hesse, Allgem. Zool., Gustav Fischer.) 93.—How THE EvE CapsuLeEs or A FLATWORM SERVE AS DIRECTIONAL ORGANS . : E Be aie) fs: (From Plate, after Hesse, Allgem. Zool., Gustav Fischer.) XXXV ILLUSTRATIONS FIGURE The arrows show the varying directions of the light. In each case only a particular part of each retina is stimulated, the rest being in shadow. 94.—Eye or Squip (HorizontaL MEDIAN SEcTION) (From Plate, after Hensen, Allgem. Zool., Gustav Fischer.) 95.—DEVELOPMENT OF THE EYE IN CEPHALOPOD Mo.uvuscs (After Plate, Allgem. Zool., Gustav Fischer.) A. Early embryonic stage, showing the spherical retina (represented in the Pearly Nautilus). B. Snaring off of the eyeball and beginning of the iris-folds and of a primary cornea. C. Development of the lens on either side of the primary cornea, or transparent septum. D. Development of a secondary or outer cornea. 96.—Licut CELLS oF Amphiozxus . A. Forepart of a young Amphiorus, enlarged, show- ing light cells (Becheraugen). (From Plate, after Joseph, Allgem. Zool., Gustav Fischer.) B. Cross-section of the spinal cord of Amphiozus, showing the light cells, which are essentially like the goblet eyes (Becheraugen) of invertebrates. (From Plate, after Hesse, Allgem. Zool., Gustav Fischer.) 97.—EVOLUTION OF THE VERTEBRATE EyE as Con- CEIVED BY STUDNICKA (From Plate, after Studnicka, Allgem. Zool., Gustav Fischer.) In still earlier stages it is supposed the vertebrate eyes arose, as in invertebrates, through a down- pocketing of the light cells (Fig. 91) on the surface of the embryonic nerve furrow, or medullary fold. When the fold closed over, as it does in the developing verte- brate embryo, the future eye spots found themselves XXXVi PAGE 179 181 183 185 ILLUSTRATIONS FIGURE in the inner lining of the nerve tube or brain, with the “rods”? turned away from the light. A. Stage in which the dorsal pair of ‘‘eyes” (pineal and parapineal) are beginning to grow outward, as well as the “‘paired”’ eyes. B. Stage in which the eye stalks are forming. C. Stage in which the lens and retina are beginning. D-I. Subsequent stages in the formation of the optic cup. 98.—TueE Ricut EYEBALL AND Its S1tx Muscues (From Plate, after Merkel and Kallins, Allgem. Zool., Gustav Fischer.) 99.—Tue Ricut Eye or A SHARK IN HorizontTaL SECTION . (From Plate, after Franz, Allgem. Zool., Gustav Fischer.) 100.—D1aGRAM OF HorIzONTAL SECTION OF THE Ricut Human Eye. (Simplified from Plate, after Luciani, Allgem. Zool., Gustav Fischer.) 101.—TEAR-DRAINING CANALS OF THE EYE (After Keith.) 102.—Front View oF INFANT AND YOUNG SKULLS or AnTHRoporps (A, B, C) anp or Man (D) A. Chimpanzee. (After Selenka.) B. Gorilla. (After Selenka.) C. Orang. (After Selenka.) D. Humanchild. (After Martin, Lehrbd. Anthropol., Gustav Fischer.) 103.—Tue Human OrGAN oF HEARING AND BALANCE ‘ : (A and C, after Cunningham.) A. Transverse section. XXXVIl PAGE 190 192 193 194 197 203 ILLUSTRATIONS FIGURE PAGE B. Diagram section of the cochlea, showing the ascending and descending spiral duct and the cochlear duct containing the organ of Corti or true organ of hearing. C. Greatly enlarged view of the cochlear duct, showing the organ of Corti with its damper, hair cells and hearing nerves. 104.—Srries SHOWING THE MEMBRANOUS LABYRINTH or INNER Ear FROM FisH To Man . . 205 (After Retzius.) Right side; outer view. Shark (Acanthias). Ganoid fish (Lepidosteus). Primitive reptile (Hatteria). Alligator. Primitive mammal (Rabbit). Man. ol es 105.—DEVELOPMENT OF THE LABYRINTH OR INNER Ear or Man . : : 3 E . 206 (After Streeter.) 106.—TRANSVERSE SECTION OF THE HEAD IN A Froc, SHOWING THE RELATIONS OF THE Mippite Ear (THERE IS NO OvteR Far) TO THE INNER EAR AND OF THE LATTER TO THE BRAIN : : : . ‘ . 208 (After T. J. Parker and W. N. Parker.) 107.—EmBryo SturRGEON, SHOWING GILL CLEFTS 209 (After W. K. Parker.) 108.—Human (A) anp Macaque (B) Empsryos, SHOWING ORIGIN OF THE EXTERNAL EAR FROM Six TUBERCLES ; : : aes || A. From Leche, after Selenka. B. From Leche, after His, Keibel. (A, B, from Der Mensch, Gustav Fischer.) XXXVIli ILLUSTRATIONS FIGURE PAGE 109.—Ears oF Fa@rat Macaque (A) AND or A Six Montus’ Human Faerrus (B) . ; 5 A (From Plate, after Schwalbe, Allgem. Zool., Gustav Fischer.) 110.—ExTERNAL Ears or ANTHROPOIDS AND MEN 213 (After Keith.) Chimpanzee. “*Small chimpanzee type’’ (human). “Chimpanzee type”’ (human). Orang. “Orang type” (human). Gorilla. Gibbon. Lemuroid (Nycticebus). Horse Onp 111.—Tue Mippie Ear or Man, SHOWING THE AupitTory OSsSICLEs . ; » 216 (After Cunningham.) A. View of the left tympanum (drum membrane) from the inner side. The ossicles are cut away except the handle of the malleus, which is inserted into the drum membrane. B. The same, showing the three ossicles in place. 112.—RELATIONS OF THE Parts oF THE MIDDLE Ear IN AN Extinct MamMat-LikE RepritE . 217 A. Side view of back part of lower jaw of Permo- cynodon, a cynodont reptile from the Permian of Rus- sia. (Mainly after Sushkin.) The broken line indicates the position of the pouch from the tubo-tympanal cavity as inferred by Watson and Sushkin. B. Rear view of the skull of Permocynodon, show- ing the perforate stapes in position. (After Sushkin.) The broken lines (added by the present author) indicate his interpretation of the position of the middle- ear chamber and of the tympanic membrane. The existence of an extra columella, as in primitive rep- XXXIX ILLUSTRATIONS FIGURE tiles, is inferred from the presence of a facet on the lower outer end of the quadrate. 113.—OrIGIN or AupDITORY OSSICLES A. Back part of the lower jaw of Cynognathus, inner side. (Based chiefly on a cast of the type of Cynognathus craternotus, combined with observations and figures of Seeley and Watson.) B. Fcetal mammal, Perameles. (Slightly modified from R. W. Palmer.) 114.—RELATIONS oF OssicLEs TO LowER JAW ON Fa:rat ArMADILLO (Tatusia hybrida) . (Composed from two figures by W. K. Parker.) 115.—TuHeE RepritiaN STAGE IN THE DEVELOPMENT OF THE AUDITORY OSSICLES A. Lower jaw and attached auditory ossicles in a foetal hedgehog (Erinaceus). (After W. K. Parker.) B. Lower jaw and attached auditory ossicles in a human foetus of 43 millimeters length. (After Macklin.) 116.—YounG CHIMPANZEE, SHOWING FacraAL ExprREs- PAGE 218 221 221 SION : : ; . facing 222 (From a photograph by Herbert Lang.) 117.—Stockarp’s LINEAR AND LATERAL GROWTH TYPES : (After Stockard.) A. Infant. B. ‘‘Linear”’ adult. C. ‘Lateral’ adult. 118.—SipE View or Human Fiacure, To INDICATE THE ANTERIOR TIP AND THE GENERAL D1IREc- TION OF THE LATERAL LINE (After Stockard.) xl 232 234 OUR FACE FROM FISH TO MAN - , an ay (At wy TERE ‘ Win , ; BA , Lie uf : ; fi " i 4 i f ari af ¢ ‘ ‘ j j hy tA 6 iar: PIAL ale } : Ave . vo F J . ay ‘ , '¢ 4 a asi yt! Bay Ari’ i ads Me 4 fe, at a7 ee oa fi iy. , i OUR FACE FROM FISH TO MAN PART I PORTRAIT GALLERY OF OUR ANCIENT RELATIVES AND ANCESTORS THE VALUE OF A FACE For a billion years or more the ceaseless game of life has been concerned with the capture and utilization of energy for the benefit of the individual and with the rhythmic storage and release of energy for the reproduction of the race. In all ages and in all branches of the animal kingdom a face of some sort has been indispensable to all but sessile animals, just because a face is concerned primarily with: The detection of desirable sources of energy; The direction of the locomotor machinery to- ward its goal; The capture and preliminary preparation of the energy-giving food. OUR FACE FROM FISH TO MAN Among the highest animals the face acts also as a lure for the capture of a mate. In nearly all the lower vertebrate animals, how- ever, the most constant and dominating element of the face is the gateway formed by the mouth and arching jaws to the “primitive gut” or digestive tract. Around this architectural centerpiece the higher facial designs gradually developed. THE BEGINNINGS OF OUR FACE Doubtless it is a far cry from the lowly Slipper Animalcule, whose face consists only of a gash in the side of its moccasin-like body, to the human face divine, but among the thousands of known living and fossil forms Nature has left us a number of significant vestiges on the long pathway of creation. Among the more primitive of the many- celied animals the jellyfishes consist essentially of a two-layered parachute-like sac, the inner layer serving as a primitive gut, the outer layer chiefly as an envelope. The mouth of the sac is greatly puckered and the folds are produced into ten- tacles, often endowed with nettle-like, stinging threads. A diffuse nerve net extends everywhere 4 OUR ANCIENT RELATIVES between the inner and the outer layer and is con- centrated into a ring around the mouth. This mouth is far from being homologous with our own. It represents at most the “primitive streak” of the early embryos of vertebrate animals. Never- Fic. 1. Tue First Movrus. Slipper animalcule (A) with gash-like mouth; Jellyfish (B), a two-layered sac with primitive mouth. (Both after Parker and Haswell.) For details, see p. xiii. theless it was the starting-point for further de- velopments. The direct line of ascent toward the vertebrates is not yet definitely known and we can only sur- mise what the next few steps may have been. The flatworms appear to represent highly devel- oped descendants of the jellyfish group, which had abandoned the drifting habits of their remote 5 OUR FACE FROM FISH TO MAN ancestors and taken to living on the bottom in shallow water. The simple pulsations of a bell- shaped body, which were sufficient for jellyfishes, were modified into writhings or contractions in definite directions. Anyhow, radial symmetry gave way to bilateral symmetry, the animals began to progress in a fore-and-aft direction and the sharp differentiation of heads and tails was in full play. The early evolution of a primitive head is also well illustrated in certain flatworms (Fig. 2A), in which the slender nerve threads are drawn together to form the first rudiments of a brain and a very simple type of eyes is attained. In the annelid worms the head is further advanced, since the mouth is now surrounded by various accessory organs for the testing of the food, by horny jaws moved by muscles for the capture of the food, by elaborate eyes and by an extensive fusion of nerve fibers into an incipient brain. The trilo- bites and higher crustaceans (Fig. 2B) carry the story onward, showing us how some of the jointed projections from the sides of the body, which had originally been developed as primitive legs, very early began to serve the mouth by drawing, kick- 6 =a | EE ae cS ee we eer | a5 nerve E — == * if | t i i I | I: ‘ =| ee =| = ZEN | oil pr B Two Earty Sraces IN THE EvouuTion or A HEAD (arTER ParKER AND HASWELL). Fig. 2. Flatworm (A), showing a _ head-and-tail differentiation, including the beginnings of a brain and of eyes; Sand-flea (B), showing the interrelations of eye, brain, mouth, leg-jaws and nerve cord. For details see p. xiii. OUR ANCIENT RELATIVES ing or pushing the food within its reach, these mouth-legs finally culminating in the various and highly refined burglar tools so well wielded by the swarming hosts of insects. According to Professor Patten of Dartmouth, the vertebrates were derived from the arachnid stem—an ancient branch of the jointed animals (arthropods), that is represented today by Limulus, the ‘“‘king-crab”’ (which is not a crab at all), and by the arachnids (scorpions and spiders). But if these disagreeable creatures are our remote rela- tives, then the highly developed head which they had acquired after so many millions of years of struggle all had to be largely made over when the vertebrate stage of organization was _ reached. They had to sacrifice their elaborate leg-jaw apparatus, their very mouths were stopped and a new mouth and jaws were formed, their eyes were turned upside down and inside out and a new set of swimming organs had to be devel- oped. According to the more orthodox view, the verte- brates from their earliest stages stood in wide contrast to the crustaceans, arachnids and insects. For while both groups comprise segmental animals, 7 OUR FACE FROM FISH TO MAN moving in a fore-and-aft direction and building up a complex head through the fusion of simple seg- ments, yet the arthropods developed their jaws out of jointed locomotor appendages while the vertebrates utilized for this purpose the cartilagi- nous bars of the first two gill pouches. According to Patten’s view the fossil ostracoderms (Fig. 4) were more or less intermediate between these two great groups; but the objections to this view are formidable. No matter from what group of invertebrates the vertebrates may have sprung, their origin took place many hundreds of millions of years after the first synthesis of living matter from less complex substances. When the first fishes took form the seas already swarmed with thousands of species of marine invertebrates,—protozoans, sponges, cor- als, trilobites, crustaceans, brachiopods, arthro- pods, molluses, etc., and so far as the marine inver- tebrates were concerned, all the major problems of feeding, locomotion, sexual and asexual repro- duction had been solved zeons ago. And when the vertebrates started on their long career they too had already solved all the same fundamental prob- lems by rigorously sacrificing much of their old 8 Yi y iy Z QR, YW Z Qn ~’W ORGANISMS Re ONE -/CELLED Fic. 3. Tue Risk or THE VERTEBRATES IN GEOLOGIC TIMES. Figures at left give estimated time in millions of years. OUR FACE FROM FISH TO MAN equipment and by profoundly changing what was left of their original heritage. The earliest known vertebrates (or more properly, chordates) are in- dubitably far nearer to us in geologic time and in the ground-plan of their whole organization than they were to the first living creatures; even their faces reveal them, as we shall presently see, as early kinsfolk of ours; the real beginnings of our facial type are either hidden in still unexplored rocks of pre-Silurian ages or wiped out forever by the destructive forces of erosion. From the view- point of earth history as a whole, even the earliest vertebrates of Silurian times (Fig. 4) rank among the younger children of life, yet from the viewpoint of mankind their antiquity is at first inconceivably vast, since according to all recent geological in- quiry, it must be reckoned in hundreds of millions of years. | The recent monographic researches of Kier and especially of Stensié upon the amazingly well preserved ostracoderms of the Silurian and Devo- nian ages of Norway and of Spitzbergen have defi- nitely shown that these curious forms are more or less directly ancestral to the hagfishes and lam- preys of the present day, which comparative 10 OUR ANCIENT RELATIVES anatomists have long regarded as standing far below the grade of the sharks in the scale of vertebrate life. In some of these fossils the infil- VASES a {QS —— SSS 58 eee. LAL | Mery =: aS Seite an ee ean, Bs , "OO lN- ——, —<, ~ ~ - SS, 2 oe on —< < We: » LEZZ2 Fig. 4. Some or Our Earutest Known KINSFOLKE. Upper SILURIAN AND DrEvoNnIAN OSTRACODERMS. For details, see pp. xiii, xiv. trated mud has made a natural cast of even the principal nerves and blood vessels of the head, so that Stensio has been able to show that they com- 11 OUR FACE FROM FISH TO MAN pare very closely in the ground-plan of the anatomy of their heads with the larval stages of the lampreys. In all these lowly creatures as well as in ourselves the head is essentially the complex of sense organs, brain and brain covering, mouth and throat, by means of which the creature is directed to its food and enabled to engulf tt. THE SHARK’S FACE AND OURS The ancestors of the higher vertebrates did not settle down and become specialized bottom-living fishes but long maintained themselves in the fierce competition of free-swimming, predaceous types. Whatever the first steps leading toward the verte- brate head may have been, the shark shows us our own facial anatomy stripped of all elaborations and reduced to simplest terms. Like Shylock, the shark might well plead that he has eyes, nose and a mouth, affections, passions; accordingly we find that in zoélogical classes all over the world the humble dogfish affords an invaluable epitome and ground-plan of human anatomy. Men have been insulted by the implications of this fact and still more by the statement that man 12 Fig. 5. Tue Face or tue Most Primitive Livinc SHARK (AFTER GARMAN). For details see p. xiv. “AIX ‘d 9as ‘sjrejop 10g ‘popddrjs aseptyavo ‘paxvodjs soposnur $9}1qM SaArou {9}ITTM YILA patapsioq (‘SITTY UAldV) “MUYVHG V dO GVa4_{ AHL NI NOISIO“UG JO SLNAWAULSNT sare 40 = abopnun) SIYISMULAL OEP TR eryypy ree oe ¢ a \ LOY DD) Al ve. voonne q ss Class AIG 1M SOYUIMONYID JO SOHISNUL pee MOpIAJSUOI POLIYLOANS ‘ YOR] s[euvo ouly [B10}eT 9 “DIY ites 2200 Ry , SLES sapasnua ied 13 OUR FACE FROM FISH TO MAN is far nearer in architectural plan to the shark than the latter is to whatever invertebrates we may choose to name as the starting-point of the whole vertebrate tree of life; but such are the secure judgments of comparative anatomy. Much that might appear mysterious and in- scrutable in the anatomy of the human face may reasonably be explained as a heritage from far-off shark-like ancestors, which human embryos also recall. Let us therefore look a little more closely into the construction and functioning of the face of this human prototype. Always remembering that the face is merely the food-detecting and food-trapping mask in front of the brain, we find in the shark’s apparently simple face a truly marvelous assemblage of instruments of precision (Fig. 6). First among these food- detecting devices rank the smelling organs, rosette- like membranes exposed in the olfactory capsules under the nostrils, capable of detecting chemically the very minute quantities of blood or other animal matter dissolved in sea water. These smelling capsules lead by prominent nerve tracts to the large forebrain, in which the smelling centers are the dominant elements (Fig. 81). 14 OUR ANCIENT RELATIVES In the brain these olfactory messages stimulate the motor nerves controlling the eye muscles and other nerves controlling the locomotor muscles, in such a way that the shark turns and moves toward the source of the odor. The eyes of a shark are fundamentally similar to those of a man but their marvelous intricacy forbids an attempt to discuss them in this brief space. Each eye is moved by six sets of eye muscles (Fig. 6), which turn the pupil toward the goal of movement. As the food is reached and the stimulation of smell, sight and other senses reaches its climax, there is a convulsive expansion of the jaws, the food is torn by the jagged teeth, the jaws snap shut with the vicious force of a bear-trap, and the intense pleasure of swallowing the precious life- giving morsel is experienced. Thoroughly equipped research laboratories could profitably occupy the time for decades to come with a study of what really happens when a shark detects its food and rushes forward to engulf it, for this apparently simple but in reality vastly complex sequence holds many secrets of vital importance to human beings. 15 OUR FACE FROM FISH TO MAN However, the fact that even the true nature of nerve currents is as yet very imperfectly known does not prevent us from realizing the value of even a homely face to all animals that navigate the waters or move upon the land or in the air. Not the least important of the shark’s detecting and navigating instruments are the very numerous “ampulle”’ that are so thickly scattered all over the surface of the head. Each of these pits is con- nected with a nerve tendril and thousands of these nerves run together into larger tracts, which finally run into the brain itself. Possibly these ampulle detect vibrations of low frequency in the water and in some way codperate with the olfactory nerves in giving stimuli proportional to the nearness of the source. Then there are the taste organs scattered over the mouth cavity, all wired most carefully and elaborately and connected with the appropriate brain centers. The so-called “internal ears’? embedded in the cartilage on either side of the hindbrain, consist chiefly of the ingenious semi-circular canals (see pages 202-6, Fig. 104), arranged like our own in 16 OUR ANCIENT RELATIVES three planes and capable of analyzing any move- ment of the body into three directional components. These instruments of precision communicate their findings to the brain and form essential partners to the instruments carried by the face. CAppsH CCS olf ¥: ot git na COMM AYES AYOA and, LG AT HOS Fig. 7. CARTILAGINOUS SKELETON OF HEAD OF SHARK, COMPRISING BRAINCASE, Primary UprpreR AND LOWER JAWS AND BRANCHIAL ARCHES. The scaffolding or skeleton of the face (Fig. 7) consists of three principal parts: first, the carti- laginous capsules (olfactory, optic, otic) that sup- port the paired organs of smelling, sight and balancing; second, the cartilaginous trough and box that enclose the brain; third, the cartilaginous upper and lower jaw-bars (palatoquadrate, Meck- by OUR FACE FROM FISH TO MAN el’s cartilage), with certain connecting bars (hyo- mandibular, ceratohyal) that tie the jaws on to the braincase. These jaw cartilages resemble the bars of cartilage (I-V) that form the supporting frame- work for the gills. LMM yO. evi amiary lls LL RR CI: 4 i 1] addu ClOr’ Bi : Fi / GT — tharaibulue wee f we Hustle COnStTICLO truscles WET GMA ACS Fie. 8. Jaw Musc es or SHARK, SHOWING THE EssENTIAL SIMILARITY OF THE JAw MUSCLES TO THE CONSTRICTORS OF THE BRANCHIAL ARCHES. For details, see p. xiv. Even the jaw muscles appear to be modified gill-arch muscles. The principal jaw muscles (Fig. 8) are simply bands or sheets of muscle wrapped around the angular bend where the upper and lower jaw segments articulate with each other. The lower jaw is pulled downward chiefly by a backward pull of the horizontal muscles. 18 OUR ANCIENT RELATIVES All these muscles, like those of the locomotor apparatus, are composed of striped muscle fibers and each little fiber is a sort of engine, deriving its fuel from the chemical glycogen in the blood and its explosive impulse from a tiny nerve fiber. Over the whole of this great complex is stretched a tough but flexible envelope, the skin, which is studded with minute teeth, or shagreen. Around the jaw-bars the shagreen gives rise to large teeth. Thus in barest outline we have the elements of the face and its connections with the braincase in the shark. If we are fond of mysticism we will say that in the cramped brain-box lives the shark himself, who receives the multitudinous messages from his detecting instruments and shapes his actions accordingly. In this anthropocentric phil- osophy a shark’s face is highly expressive of the shark’s piratical and cruel character. If we wish to be thoroughly behavioristic, on the other hand, we will regard the shark’s conduct as the automatic resultant of the various stimuli received by his sensorium, which were transmitted to the complex apparatus in the central nervous system, the office 19 OUR FACE FROM FISH TO MAN of which in turn is to play off one stimulus against the other and to shape the motor responses into profitable combinations. In this case the shark’s face is innocent of cruelty or piracy and is merely an assemblage of coérdinated instruments of pre- cision packed into the forepart of a vessel of appropriate streamline form. At this place we do not have to discuss what brought about this marvelous aggregation of codrdinated apparatus. All we need emphasize is that in the face of a shark a man may behold, as in a glass darkly, his own image. Nevertheless a man should not flatter himself that he is a direct descendant of some powerful robber-baron such as the tiger-shark. Always in earlier times we have been only the little stealers of small fry and even when we attained the mammalian grade we were still specializing in capturing small living things. THE MASK-FACE OF OUR GILLED ANCESTORS A skull finds but little favor with the man in the street and possibly it would not interest him much to be told that every one of his twenty-eight skull bones has been inherited in an unbroken 20 AIx ‘d 9as s[lejap 10q ‘(UHONVG UALAV) STIG ANOG AHL ONIMOHG ‘HSI. GIONVY) TISSOY V dO T104¥Q FHL JO NOILOGS-SSOUD ‘6 “DIY OUR ANCIENT RELATIVES succession from the air-breathing fishes of pre- Devonian times. However, we wish to go even back of that and are curious to know why animals ever acquired a skull at all. The “basic patent” for the strength- ening of all skeletal parts is the bone-cell, which invades both the skin covering the head, where it forms “derm bones,” and the underlying carti- lage or braincase; everywhere it deposits phos- phate of lime and other salts, thereby greatly stiffening the skin and strengthening the brain-box. The skull of all vertebrates above the sharks is a complex bony structure consisting of an outer shell, or dermocranium, originally derived from the many-layered skin, and an inner skull, or endocranium, derived from the cartilaginous brain- trough and its associated three pairs of capsules for the nose, eyes and inner ears. The same kind of cells surround the elastic notochord or primitive axial rod, and deposit the bony tissue along certain tracts between the tough membranes that separate the muscle segments. In this way rods called ribs are produced as well as the bony arches above the notochord. All this results in a strong framework, which supports the 21 OUR FACE FROM FISH TO MAN powerful body muscles that drive the body through the water. The braincase is the thrust-block (Fig. 10) that receives the forward push from the backbone and Fie. 10. Tar WernpGr-sHAPED BRAINCASE OF A FisH, ACTING AS A THRUST-BLOCK OR FULCRUM FOR THE BACKBONE. For details, see p. xiv. the reaction from the water. The roofing bones over the braincase and the keel bone (parasphenoid) on the under side of the braincase together form a long wedge which is thrust forward into the water. To the sides of the skull are attached first, 29 crag Sis . “* =Ts oe Se sate Fic. 11. Tue Factan Armor AND Jaws or A Dervontan LOBE-FINNED Ganorp Fisu (AFTER PANDER). The skull seen from above. For details see p. xiv. hen ‘ i OA) SEs DrvVoNIAN ‘‘ LOBE-FIN” (AFTER BRYANT). First CLAIMANT TO THE LINE oF ANCESTRY OF THE HIGHER VERTEBRATES. Fig. 12. For details see p. xv. OUR ANCIENT RELATIVES the complex jaws, consisting of the primary or originally cartilaginous upper and lower jaws plus their bony dermal covering, and second, the sliding bony covers of the gill chamber. In the modern sharks the skeleton is stiffened by calcium carbonate rather than by phosphate of lime, the skin is stiffened chiefly by the shagreen or little teeth on its surface and the skeleton as a whole remains in a low stage of evolution. On the other hand, in the ancient lobe-finned ganoid fishes, which stand much nearer to the direct line of human ascent than do the sharks, phosphate of lime is deposited by true bone-cells and the skull comprises a bony mask and a bony braincase as described above. The whole surface of the mask (Fig. 11) is cov- ered by a thin enamel-like layer, smooth and shining, called ganoine. The jaws of the ancient ganoids, well covered both on the inner and outer sides by an armor of bony dermal plates, carried large sharp teeth with deeply infolded or labyrinthine bases (Fig. 18A). There is every reason to regard these mail-clad robbers as lying not far off the main line of ascent. The alligator-gar of the lower Mississippi system, 23 OUR FACE FROM FISH TO MAN although belonging to another order of ganoid fishes, bears a striking general resemblance to its Devonian relatives. Among these ancient ganoid fishes there are two groups that have claims for the honor of standing nearest to the main line of ascent. The first lot were fierce, predatory, pike-like forms, which had stout fan-shaped paddles, two pairs, corresponding to the fore and hind limbs of land-living verte- brates. To judge from the fact that they had internal nares or nostrils as well as external ones, these ancient lobe-finned ganoids already possessed a lung in addition to gills and were therefore able to breathe atmospheric air directly when the streams and swamps in which they lived tem- porarily became dry. Today this group of lobe- finned or crossopterygian ganoids is represented, if at all, only by two living genera of fishes: the bichir (Polypterus) of the Nile and its elongate relative Calamoichthys. In its mode of embryonic development Polypterus shows resemblances both to the lung-fishes and to the Amphibia. The rival claimants for the honor of standing in the human line of ascent were the true lung-fishes, or Dipnoi. The several survivors of this group at 24 DEVONIAN DrpNoAN (AFTER PANDER). Seconp CLAIMANT TO THE LINE or ANCESTRY OF THE HIGHER VERTEBRATES Fig. 13. For details see p. xv. OUR ANCIENT RELATIVES the present time, including the famous lung-fish (Neoceratodus) of Australia, all have very well- developed and functional lungs in addition to gills. Moreover, the embryonic development of the mod- ern lung-fish, it has been shown, closely parallels that of certain existing salamanders. Nevertheless, all the fossil and recent fishes of this dipnoan group had definitely and hopelessly removed themselves from the main line of ascent, since they had already either reduced or lost the marginal bones of the upper jaw and had developed peculiar and specialized fan-shaped cutting plates on the roof of the mouth and on the inner side of the lower jaw. The earliest of the land-living or four-footed vertebrates, on the contrary, retained the marginal jaw bones and never developed the fan-shaped cutting plates on the roof of the mouth. To make a long story short, the real ancestors of the higher vertebrates were probably neither true dipnoans, nor any of the Devonian lobe-finned ganoids, but were the still undiscovered common ancestors of these rather closely related groups living somewhere, perhaps in Lower Devonian or Upper Silurian times. 25 OUR FACE FROM FISH TO MAN The evidence of embryology and comparative anatomy points unmistakably to the derivation of the land-living vertebrates from air-breathing fishes, with stout paired fore and hind paddles and a complex skull of the general type described above. The lobe-finned fishes as a whole appear to be Fig. 14. Emsryos or Moprern LosBe-FINNED Fisu (A) (AFTER Bup- GETT) AND AMPHIBIAN (B) (Arter S. F. CLARKE). For details, see p. xv. near to the direct line of ascent, although each of the known members of the group is probably too late in time and too specialized in certain details of skull structure to be the actual ancestor of the land-living vertebrates. In view of the mobility and fleshiness of the human and other mammalian faces it may be 26 OUR ANCIENT RELATIVES deemed surprising that one should seek to derive the higher vertebrates from fishes whose whole head and face were covered with a porcelain-like armor; but in the following pages we shall follow this amazing transformation step by step. OUR ANCESTORS COME OUT OF THE WATER Plant life is believed to have originated in the sea in early Archeozoic times. As far back as Devonian time it had succeeded after long ages of struggle in adapting itself to terrestrial life and there were great forests of low types of trees pre- ceding the still greater swamps of the Coal age. No remains of amphibians have hitherto been found associated with Devonian plants, and the transformation of air-breathing fishes into lowly amphibians took place during the millions of years in which the fossil record of vertebrate life is still defective. But at the time of the formation of the older coal beds of Great Britain there were still surviving some very low types of amphibians which retained more of the fish-like characters in the skeleton than did any later forms known. These highly interesting remains were imper- fectly described by earlier authors but they have 27 OUR FACE FROM FISH TO MAN been successfully restudied by Professor D. M. S. Watson of University College, London, in the light of his extensive knowledge of later fossil amphibians. Under his keen scrutiny these oldest known land vertebrates have yielded many facts of far-reaching significance. He has shown that in certain of these forms the shoulder-girdle was Fic. 15. One or tHe Most Primitive KNown AMPHIBIANS FROM THE LowrR CARBONIFEROUS OF ENGLAND (RESTORATION AFTER Watson’s Data). For details, see p. xv. still attached to the skull by a bony plate, as it is in typical fishes, and that the bony plates of the shoulder-girdle were still readily identifiable with those of fishes, whereas in later types these plates became highly modified. The bony mask covering the face and braincase of these oldest tetrapods’ is of the greatest interest in the present connection, for in it we find the starting-point for everyone of the twenty-eight A name often applied to the oldest four-footed land-living forms, both amphibians and reptiles. 28 Fic. 16. Skutt or One or THE OtpEst Known AMPHIBIANS (Loxomma allman‘). After Embleton and Atthey. A. Upper surface. B. Under side. ited %* ma = : +, ; > ? o = : =, | 7 Se 7 < 7 af ao 2 7 aa ma — _ > ; er a " ae " a" ey = : : - = 7 - 7 bs ob és ’ 7 oe 6 Ae ee vert 'y wee a ae OUR ANCIENT RELATIVES bones of the human skull, together with many other bony elements which were reduced and gradually eliminated in the long procession of forms from fish to man. Before looking forward to man, let us look back- ward and see how the skulls of these earliest explorers of the land compared with those of their collateral ancestors, the air-breathing, lobe-finned ganoids. The greatest change is seen in the region of the gill chamber, just behind the upper jaws. In the fish this was covered by a beautifully jointed series of bony plates, as perfectly articulated as any suit of armor ever made by man. In the oldest amphibians, however, these bony plates behind the jaws have disappeared completely, leaving an exposed area called the otic notch just behind the upper jaw. ‘This is the region of the middle ear or sound-transmitting apparatus in modern amphi- bians and apparently these ancient amphibians had already acquired this new instrument of pre- cision. In the lower jaw the bony plates covering the under surface of the throat had also dis- appeared. In the region above the nostrils the mosaic of small bones found in the lobe-finned 29 OUR FACE FROM FISH TO MAN fishes had been replaced by two large bones hence- forth traceable directly to the nasal bones of man. The several bony plates on the face surrounding the eye had also been changed in proportions. 125 TL a mt | ae Rae 4 ea oes Z LZZFFF Hit: MArGiNA giklars Fia. 17. Sxuits or Lopu-rivnep Fism (A) anp Earty AMPHIBIAN (B), SHowrna Loss or OpERCULAR SERIES IN THE LATTER (A, aArrER TRAQUAIR AND Watson, B, AFTER Watson). In the primitive amphibians the space formerly covered by the opercular region was covered by the tympanum or drum membrane. For details, see p. xv. 30 Fic. 18A. Cross-section or LasyrintHODONT TEETH. LOBE-FINNED Fic. 18B. Prraitive AMPHIBIAN OF PerMIAN AGE (AFTER Devonran Fisu (arrer PANDER). EMBLETON AND ATTHEY). For details see p. xvi. OUR ANCIENT RELATIVES On the other hand, many of the bony plates of the skull roof were taken over with little change by these oldest amphibians and the same is true of the derm bones of the lower jaw. On the under side of the skull (Fig. 53) the parasphenoid or keel bone had grown backward so as to cover the base of the braincase. The teeth of the oldest amphibians were closely similar to those of the lobe-finned ganoids, both in general appearance and in microscopic structure. The porcelain-like outer layer of the skin bones covering the head of the lobe-finned fish had dis- appeared, leaving arough surface. Thus the face of the oldest known amphibian, still consisting chiefly of a bony mask, was not as different from that of a lobe-finned fish as one might have expected. Truly Nature’s ways are not as man’s ways. After producing a beautiful mask-face of great perfection and serviceableness, Nature started in to reduce and simplify it and eventually to cover up this mask with tender, sensitive flesh. From now on, the story of the human skull is the story of simplification and sacrifice of numbers, together with the refinement and constant differentiation of the elements that remained. $1 OUR FACE FROM FISH TO MAN WHAT WE OWE TO THE EARLY REPTILES The recent frogs, newts and salamanders, as every high school student knows, go through a fish-like or tadpole stage of development in the water and resort to this ancestral medium at the breeding season. The presence of fossilized gilled young of amphibians in the Coal ages shows that this water-breeding habit dates back very early in geological time and is in harmony with the origin of amphibians from swamp-living fishes. A great and revolutionary advance occurred when some daring amphibians succeeded in raising their eggs entirely on dry land, for thus arose the rep- tilian grade of organization and with it came the possibility of all higher forms of life, including man. With regard to the bony face, the most primitive known reptile, Seymouria, has much in common with the older amphibians. It still retains the otic notch characteristic of the older forms and on its skull roof it preserves the full complement of small bony plates inherited from the amphibians and lobe-finned fishes. Also its outer upper jaw bones (maxillz) still retain their primitive slenderness. In the same age which yielded Seymouria (the 32 OUR ANCIENT RELATIVES Permian of Texas) lived another, decidedly higher reptile, which had already acquired a significant resemblance to some of the lower mammal-like Fic. 19. Two Criticat STAGES IN THE EARLY EvoLutiIOoN OF THE SKULL. A. Generalized reptile, retaining the full complement of amphibian skull elements. (After data of Broili, Watson, Williston.) B. Primitive theromorph reptile, with reduced number of skull elements (after Williston). For details, see p. xvi. 33 OUR FACE FROM FISH TO MAN reptiles of South Africa. This interesting form (Mycterosaurus) was carnivorous, like other pro- gressive reptiles, but had not become too far specialized in this direction. The most remarkable feature of its skull is a circular hole on the side of the skull behind the eye. This perforation in the bony mask of the temporal region was the first foreshadowing of the “tem- poral fossa”’ of the human skull. As to the origin of this opening, studies on recent and fossil skulls of many kinds of reptiles indicate that the perforation arose through the progressive thinning of the bone, due to the absorbent action of the membranes surrounding the jaw muscle, which was attached to its inner surface. Mean- while, in resistance to the stresses induced by the same muscle, the borders of the muscle area became strengthened into bony bars or ridges. The bony tract below the temporal opening dis- tinctly prophesied the mammalian zygomatic arch, the cheek bone of man. Another progressive character of Mycterosaurus is the vertical growth of the upper jaw bone (maxilla), which up to that time had remained a shallow bar in front of the eyes. In the lower 34 OUR ANCIENT RELATIVES jaw the principal tooth-bearing bone, or dentary, one on each side of the head, was relatively larger Fig. 20. Sxuxiis or EARLIER AND LATER MAMMAL-LIKE REPTILES FROM SouTH AFRICA. (Data from Broom, Watson, Houghton.) For details, see p. xvi. as compared with the other bony plates of the jaw lying behind it, than it had been in earlier stages. 35 OUR FACE FROM FISH TO MAN The next stage in the long ascent is found among the extinct mammal-like reptiles of the Karroo system of rocks in South Africa. Among these the lowest (Fig. 20A) are nearly as reptilian as lizards, while the highest (Fig. 20B) almost reach the mammalian grade of organization. The bony mask skull advances in various details toward the mammalian type especially in the modelling of the lower jaw, in the further development of a temporal fossa, or muscle opening, and of a cheek arch essentially of mammalian type. THE ONE-PIECE JAW REPLACES THE COMPLEX TYPE In later members of the series leading toward the mammals the dentary bone increased in size until it so far dominated over the elements behind it that finally they were crowded out entirely and the lower jaw of the adult thus came to consist solely of the two dentary bones (one on each side) connected at the front end, or symphysis. This result was fraught with momentous consequences for the further evolution of the bony face toward the human and other mammalian types. Meanwhile the dentary bone (Fig. 21) by reason of its enlargement came eventually to press against 36 ——— fe = Ves < YY Ss Fig. 21. ProcressivE UrpcrowtH OF THE DENTARY BONE OF THE Lower Jaw to Form a New JOINT WITH THE SKULL. C. Primitive mammal. For details, see p. xvi. A. Primitive mammal-like reptile; B. Advanced mammal-like reptile; 37 OUR FACE FROM FISH TO MAN the very jaw muscles in which its upper end was embedded. In other cases when a muscle mass becomes subjected repeatedly to new pressures or friction across its line of action the surrounding BURSA (CAVITY OF MENISCUS) ftps eniet cc ude ie t au wit M" ‘ p ‘ weap ACL, A Aa oy Kl i " NK iN iil ud hy eae igs enc EX7 FIER USC ~~~ -MCK. CONDYLE 27: OF JAW i ‘ Fig. 22. Origin ofr THE INTERARTICULAR Disc, or Meniscus, Lyne BETWEEN THE LOWER JAW AND ITs SOCKET IN THE Sxuty. (Arrer GauppP.) membranes give rise to a cushion or sac of con- nective tissue filled with a clear liquid, which serves to prevent the opposing surfaces from grinding against each other. In an early embryo (Fig. 22) of a primitive mammal (Perameles) Professor E. Gaupp; the eminent comparative anatomist of Fribourg, found that a part of one 38 OUR ANCIENT RELATIVES of the jaw muscles (the external pterygoid) during the course of its development passed between the lower jaw and its socket in the skull and there gave rise to the bursa or cushion (meniscus); this disc in all typical mammals prevents the lower jaw bone from grinding into its socket in the temporal (squamosal) bone. In the immediate ancestors of the mammals the pressure of the dentary bone of the lower jaw transmitted through the meniscus or interarticular disc somehow resulted in the formation of a corresponding socket in the squamosal (temporal) bone of the skull. Thus a new or mammalian joint was formed between the dentary bone of the lower jaw and the skull, while the old or reptilian joint, lying between the quadrate bone of the wpper jaw and the articular bone of the lower jaw, was now greatly reduced in size, continued in the service of the middle ear and gave up its jaw-supporting function. These great changes made possible all the new lines of evolution of the teeth that the mammals developed, which had never been possible for the reptiles; with these improved dental equipments the mammals soon overran the world, driving out 39 OUR FACE FROM FISH TO MAN the reptiles and finally producing the primates, which eventually gave rise to man. Thus the human face owes the fundamental plan of its wpper and lower jaws to the mammal-lke reptiles and earliest mammals in which these im- provements were first worked out. OUR MASK-FACE BECOMES MOBILE The origin of the mammals is one of the most dramatic incidents in the whole story of human transformation from fish to man. The central problems set for the mammal-like reptiles were to speed up all their vital processes and to maintain them at a relatively high level; also to resist the extreme changes of temperature of the harsh, highly variable climates then prevalent, when periods of glaciation alternated with tropical heat. Means had to be found to insulate the body in slowly conducting substances so as to defy the cold; on the other hand, to enable the body to cool itself safely when over-heated. Reptiles have this power to a limited degree but it is greatly enhanced in the mammals. For this purpose many “basic patents” had to be worked out in the heat- conserving organs, in the circulation of body 40 OUR ANCIENT RELATIVES fluids, in the breathing organs. The locomotor machinery was vastly improved, the brain and nervous system had to keep pace with the general advance and a new and much less wasteful method of reproduction had to be perfected. Among the heat-regulating devices arising in the mammals, we note the following: (a) the dia- phragm, a complex structure arising from the conjunction of various muscle layers of the neck and abdomen; it acts as a bellows to draw fresh air into the lungs and thus to increase the con- sumption of oxygen; the liberation of heat is a by-product; the glands in the skin multiplied and gave rise to (b) sebaceous glands, pouring out a wax-like substance that tends to keep the skin soft and pliable; (c) sudoriparous or sweat glands, lowering the body temperature by evaporation of the exuded moisture. Chief among the heat-retaining structures was (d) the hair, which seems to have arisen from small tactile outgrowths of the skin. These at first grew out between the scales and later supplanted them. We do not know exactly when this substitution took place, as the skin of soft-skinned animals is very rarely, if ever, fossilized, but the later mam- 41 OUR FACE FROM FISH TO MAN mal-like reptiles of the Triassic age were already so far advanced toward the mammalian grade that it would not be surprising if the initial stages in Fig. 23. Oriein or THE Factat Muscures or Man. A. Primitive reptile with continuous bony mask covering skull. The mask was covered with thick skin without muscles, as in the alligator. (After Williston.) B. Modern reptile with an open or fenestrated skull covered with thick, non-muscular skin. (From Fiirbringer, modified from Ruge.) C. Primitive mammal in which the sphincter colli system has grown forward over the face. D. Gorilla. E. Man. (C,D and E after Ruge.) For details, see p. xvii. 42 OUR ANCIENT RELATIVES the formation of hair had already begun in them. At any rate, there is evidence that the bony mask of the earlier reptiles was already beginning to become leathery on its outer layer. Even in the most primitive of living mammals the hard bony mask of the face has already begun to sink beneath the surface and a more or less pliable skin has been developed. But the most remarkable fact is that as the bony mask sank beneath the surface the “facial muscles,” so char- acteristic of mammals alone among vertebrates, came into being. Where did they come from? In the reptiles the neck and throat are covered by a thin wide band of muscle called the primitive sphincter colli, which is activated by a branch of the seventh cranial nerve. In mammals this muscle, besides giving rise to the platysma muscle, has grown forward between the bony mask and the skin, along the sides and top of the face. As it grew forward over the cheek it sent out various subdivisions which either surrounded the eyes, or covered the forehead and cheeks, or surrounded the lips, or connected the lips with the cheeks, or were attached to the ears. Whenever the muscle mass sent forth a new branch it also sent into this 43 OUR FACE FROM FISH TO MAN branch a twig from the main facial division of the seventh nerve (Fig. 24). Thus what are called the mimetic or facial muscles of mammals arose by the forward migration and subdivision of a muscle formerly covering the neck. For this doc- Fic. 24. DracramM SHOWING THE CHIEF BRANCHES OF THE FactAL NERVE. A. Gorilla. (After Ruge.) B. Man. (After Weisse.) trine the anatomists Ruge and Huber have brought forward the most detailed and convincing evidence. Thus while mammals were exposed to cruel lacerations of the tender facial muscles, these same muscles became of great use in moving the lips, in closing the eyes, in moving the external ears and finally, in the apes and man, as a means of expressing emotion. 44 OUR ANCIENT RELATIVES OUR LONG-SNOUTED ANCESTORS CROWD OUT THE DINOSAURS For many millions of years during the Age of Reptiles the ancestral mammals enjoyed all the advantages of a higher level of vital activity, a higher body temperature, a better locomotor system, larger brains and more economical repro- ductive methods, which had made them far supe- rior in grade to the group from which they sprang. Nevertheless, in all parts of the world where fossils have been found these advantages did not enable the mammals to supplant immediately their swarm- ing relatives the reptiles. On the contrary, the reptilian class, which very early broke up into many orders, including the turtles, lizards, snakes, crocodilians, dinosaurs, birds, flying reptiles and many others, for millions of years dominated the earth, while both the mammals and the birds remained small and inconspicuous. For all the millions of years during which the dinosaurs ruled the land, the fossil record of life as it is preserved in Europe and North America so far reveals extremely few mammalian remains, and these only from very thin layers in widely separated parts of the world. 45 OUR FACE FROM FISH TO MAN AAA IAIN = 4c MAMMALS || BIRDS) S| ||!" i) RECENT iF PLEISTOCENE LIOCENE MIOCENE raea | —Se es ROR OOK RK ROL KK Ley oO = @ i] Qa m7 = m mo >) Qa m TERTIARY or CANOZOIC ERA vi y eal S i] m ee 4 BOOK KOO C3 x4 re ic imum] (<=. (a (a) SS a _ SST; = 12 ——————— Ne —— Rg Se) Re Sex ASSIC | BS od J UR SS] bes KSA RoI 121 1 oi AC i ees. xo Begece TRIASSIC | BSS iS . oS iS » POO? POO POC 9. ° LL asec oe “J PERMIAN | Bax od P= SO] xO 40 oe", iN yas > UPPER CARBO- | fd NIFEROUS 7 PENNSYLVANIAN SECONDARY or MESOZOIC ERA PRIMARY or PALAOZOIC ERA Fic. 25. Succusstve DomInANCE OF THE AMPHIBIANS, REPTILES, MAMMALS AND Brirps, MAN. Numerals at left stand for millions of years since beginning of period, according to rate of ‘‘radium emanation” from uranium minerals, based on Barrell’s estimates. 46 Fic. 26. Tue Common Opossum, A “Livina Fosstn’”” FROM THE AGE OF DINOSAURS. OUR ANCIENT RELATIVES The known mammalian remains from these great formations consist mostly of very fragmen- tary jaws, with a few teeth in them, of tiny mam- mals. Most of these mammals were no bigger than mice, but in the closing stages of the Age of Reptiles a few of them became as large as beavers. Some of the mammals of the Age of Reptiles in Europe and North America are believed by certain authorities to be related to that most archaic of mammals, the egg-laying Platypus of Australia. Others seem to have been remotely related to the existing marsupials or pouched mammals, which today live chiefly in Australia. The most primitive marsupial of today, how- ever, is the common opossum of North America, which is one of our oldest “living fossils.” It is, in fact, the little-changed descendant of a group of mammals that lived in the latter part of the Age of Reptiles. One of these ancestral opossums, represented by a fossil jaw and parts of the skull (Fig. 27), was found by Barnum Brown embedded beneath a large dinosaur skull in Upper Cretaceous rocks of Montana. This form, named Eodelphis (dawn-opossum) by Dr. W. D. Matthew, has the known jaw and skull parts so nearly like those of 47 OUR FACE FROM FISH TO MAN its modern relative that we can actually fit the contours of the fossil opossum skull fragments into the skull of a recent opossum with very little adjustment of the latter; so that we may safely study the lowly ‘possum as a representative and Fig. 27. Sxkuxiut Parts or Extinct Opossum, SUPERPOSED ON OvuTLINES oF SKULL oF Recrent Opossum. For details, see p. xvii. descendant of the pouched mammals of the latter part of the Age of Reptiles. Even the modern opossum skull is at first sight strangely similar to that of one of the mammal- like reptiles of the far-off Triassic. It will easily be seen from Fig. 28 that the opossum, like any primitive mammal, has inherited the entire ground- plan of its skull from its progressive reptilian ancestor. Considering the great advance in gen- 48 OUR ANCIENT RELATIVES eral grade of organization described above, it is surprising that in the side view of the skull the Fic. 28. Skutus or (A) Apvancep MamMaAL-LIKE REPTILE AND (B) MoprerNn Opossum. For details, see p. xvii. higher structural level of the opossum is indicated chiefly by the few conspicuous features figured below (Figs. 48-52). The jaw muscles of the opossum now cover the parietal and part of the 49 OUR FACE FROM FISH TO MAN frontal bones, whereas in the earliest stages they lay beneath these bones. Fie. 29. Lone-snoutep RELATIVES OF OURS FROM THE CreTAcrous oF Monaouia. (RESTORATIONS.) For details, see pp. xvii., xviii. It has been explained above how this shift in relations began, by the overlapping of the edges 50 OUR ANCIENT RELATIVES of these bones by the jaw muscles, which finally crept over and completely submerged the bone. Thus by the time we reach the primitive mammal stage of evolution almost the entire bony mask, which had originated as the bony skin on the sur- face, is now found covered by the facial and jaw muscles. | The relatives of the opossum and other primitive pouched mammals until several years ago were the only mammals of Cretaceous times of which anything definite was known as to their skull structure. In 1924 and 1925, however, Roy C. Andrews and his colleagues of the American Museum of Natural History discovered in the Cretaceous formation of Mongolia half a dozen imperfectly preserved skulls which appear to represent the forerunners of the higher or placen- tal mammals (see also Fig. 77 iv below). These little skulls, which have been described by the present writer with the collaboration of Dr. G. G. Simpson, bring strong evidence for the conclusions of Huxley, Henry Fairfield Osborn, Max Weber, W. D. Matthew and others that the remote ancestors of the placental or higher mammals of the Age of Mammals were small insectivorous on OUR FACE FROM FISH TO MAN animals with sharp cusps and blades on their tritubercular or triangular upper molar teeth. In these little Cretaceous placentals the skull and teeth were in many ways like those of certain existing insectivorous mammals, such as the tenrec of Madagascar. All the evidence available from several sources indicates that the remote ancestors of the line leading to all the higher mammals, including man, were small long-snouted mammals, of insectivorous habits and not unlike some of the smaller opossums and insecti- vores in the general appearance of the head. BETTER FACES COME IN WITH LIFE IN THE TREE-TOPS Immediately upon the close of the Age of Reptiles the mammals appear in certain regions in North America and Europe in great numbers and variety. Palzontologists think it probable that they came from Asia, possibly by way of the Behring Straits land-bridge. In the Basal Eocene or Paleocene rocks of New Mexico and a few other places have been found thousands of fragments of fossilized jaws and teeth and several incomplete skeletons of mammals, ranging in size from mice 52 Fic. 30. Tur Pren-rattep TREE-SHREW OF BoRNEO. A “living fossil” representing a little-modified survivor of the Cretaceous ancestors of the Primates. (Based on photographs and data given by Le Gros Clark.) . BN H ed Fic. 31. Tue Specrrat Tarster or Borneo. A highly specialized modern survivor of a diversified group of Primates that lived in the Lower Eocene epoch over fifty million years ago. (Data from specimen and photograph by H. C. Raven.) OUR ANCIENT RELATIVES to large badgers. These belong mostly to wholly extinct families of placental mammals, usually with very small brains and teeth variously adapted for eating insects, flesh or vegetation. In the Basal Eocene formation of Montana have been found teeth and bits of jaws of mammals that apparently were somewhat nearer to the line of human ascent. One lot of teeth and jaws appear to be related remotely to the existing tree- shrews of the Indo-Malayan region. These little animals in many ways approach the lowest of the Primates, especially in the construction of the skull and teeth. The second lot of teeth from the Basal Eocene of Montana are judged by Dr. Gidley of the U. 5. National Museum to be related distantly to the existing tarsier of Borneo and the Philippine Islands. These very curiously specialized noc- turnal primates (Fig. 31) have enormous eyes, large but simple brains, very short noses and very long hind legs, upon which they hop about among the trees. In brief, the tarsier family appears to be one of those numerous groups that after attain- ing a high level of general organization at a rela- tively early period, start off on an extremely 53 OUR FACE FROM FISH TO MAN specialized side line and thus remove themselves from the direct line of ascent to higher forms. Much more conservative and central in struc- tural type are the fossil primates of the extinct family Notharctide from the Eocene of Wyoming and New Mexico. The fossil skeletons of these animals (Fig. 32) have grasping hands and feet of the tree-living type preserved in the modern lemurs of Madagascar. The same is true of the feet of the extinct lemuroid primates of the family Adapide from the Eocene of Europe. Comparative anatomical and paleontological evi- dence unite to support the view that all the primates first went through an arboreal stage, some of them afterward coming down to the ground and carrying with them many of the structural “patents” acquired during their long schooling in the trees. The hind foot of all known fossil and recent primates below man is of the tree-grasping type with a divergent great toe and there is no substan- tial doubt, after the exhaustive critical discussions of this subject by Gregory (1916, 1921, 1927), Miller (1920), Keith (1923), Schultz (1924), Mor- ton (1924, 1927) and others, that the whole order was from its first appearance primarily tree-living 54 SKELETON OF A Primitive Fosstn PRIMATE FROM THE Eocene or Wyomina (AFTER GREGORY). Fig. 32. For details see p. xviii. OUR ANCIENT RELATIVES in habit and that the foot of man has been derived from a grasping type with a divergent great toe. Tree-living, possibly combined with nocturnal habits, favored the evolution of keen sight, and in the oldest known skulls of primates, from the Fic. 33. Sxuxty or A Priamtive Primate or THE Eocene Epocu (AFTER GREGORY). For details, see p. xviii. Eocene perhaps fifty million years ago, we find the eye orbits already larger and better defined than those of contemporary terrestrial mammals. The skull of one of the best known members of this group is drawn in Fig. 33, from fossil speci- mens in the American Museum of Natural History. In this form the chief advance beyond the primitive mammalian type (Fig. 27) is seen in the increase in the size of the eyes and the beginning of the 55 OUR FACE FROM FISH TO MAN shifting of the eyes toward the front of the head. The muzzle, or olfactory chamber, is not yet reduced. The still surviving primates afford a remarkably well graded series of faces, from the fox-like face of Lemur (Fig. 34A) to the quaint old-man-like faces of some of the Old World monkeys (Fig. 34C). In the lower forms (Lemur, etc.) a rhinarium, or moist patch, is present at the tip of the long snout, the opposite lips are separated by a notch in the mid-line and lack the mobility seen in the higher forms. In the latter, with the shortening of the muzzle, the rhinarium gives place to a true nose, the mucous-secreting skin being limited to the inner side of the nostrils and the nose eventually growing out between the nostrils. Meanwhile the opposite upper lips have become more broadly joined at the mid-line and finally the lips become highly protrusile through the constricting action of the strong orbicularis oris muscle. In the New World, or platyrrhine, monkeys (Fig. 34B), which appear to represent an independ- ent offshoot from some primitive tarsioid stock, the nostrils are widely separated, opening out- wardly on each side of the broad median part of 56 \ Xs Wa av ASCENDING GRADES OF Faces IN THE LOWER PRIMATES (AFTER ELLioT). Fig. 34. A. Lemur; B. South American monkey; C. Old World monkey For details see p. xviii. OUR ANCIENT RELATIVES the nose. In the Old World, or catarrhine series (including the monkeys, apes and man), the nos- trils are drawn downward and inward toward the mid-line, so that they tend to make a V, with the tip pointing downward. The subsequent history of the nose and lips will be considered below (pages 129, 153). The external ears of the lower primates also show many gradations from a more ordinary mammalian type (see below, pages 211-213) to the man-like ears of the chimpanzee and gorilla. The habit of living either in trees or in a forested region, in so far as it afforded opportunities for securing insects, buds, tender shoots and fruits, made possible the various lines of evolution of the teeth which we observe in studying the fossil and recent primates. In the earliest forms the denti- tion as a whole retains clearer traces of an earlier insectivorous stage, with triangular sharp-cusped upper molar teeth. In the anthropoid the habit of eating tender shoots and buds is reflected in the molar teeth, which now have broad crowns with low-ridged cusps. The human dentition, while secondarily adapted for a more varied diet, still bears many indubitable traces of its derivation 57 OUR FACE FROM FISH TO MAN from a primitive anthropoid stage like that of the fossil apes Dryopithecus and Swapithecus. Fig. 35. Tor Virw or THE SKULL IN REPRESENTATIVES OF SIX Fami.ies oF PRIMATES, SHOWING THE More Forwarp DIRECTION OF THE ORBITS IN THE HiGHER Forms. A. Fossil lemuroid; B. African lemur; C. Tarsier; D. Marmoset; E. Gibbon; F. Chimpanzee. For details, see pp. xviii, xix.’ In some of the existing lemurs of Madagascar that retain the fox-like muzzle with its large smell- ing chamber, the eyes are less enlarged and look 58 Fig. 36. Sipe Virw or SKULLS or PRIMATES, SHOWING PROGRESSIVE SHORTENING OF THE MuvzzLtE, DowNWARD BENDING OF THE Facer Bretow tHe Eyres AND ForwARD GROWTH OF THE CHIN. A. Eocene lemuroid; B. Old World monkey; C. Female chimpanzee, D. Man. (B and C after Elliot.) For details, see p. xix. 59 OUR FACE FROM FISH TO MAN partly outward as well as forward. But in all the more advanced lemuroids the eyes are larger, with more or less protruding orbits which tend to shift forward, finally restricting greatly the interorbital space and nasal chamber. This process culmi- nates in the nocturnal galagos and in Tarsius (Fig. 31), in which the eyes are enormous and the eyes themselves are directed forward, although the orbits are directed obliquely outward. In none of the lower primates, however, are the bony orbits directed fully forward and in none of them are the upper jaws prolonged downward beneath the eyes, as they are in the monkeys, apes and man. The families of man, apes, monkeys, tarsioids, lemurs and tree-shrews are exceedingly rare as fossils except in a few localities and geologic horizons and the known remains usually consist chiefly of broken jaws with a few teeth. Never- theless these fossils are of high value when studied together with the manifold families, genera and species of primates still living. In a series of publications beginning in 1910 I have shown how fully these recent and fossil forms, from tree- shrews to man, reveal the structural stages in the 60 Fic. 37. Eprrrome or THE Fos- sit History or HuMan AND PREHUMAN PRIMATES. A. Tree-shrews (after Simpson; back part of jaw from modern tree-shrew); B. Primitive lemu- roid (after Matthew); C. Proto- anthropoid; D. Proto-anthropoid (C and D after photograph by McGregor); E. Man-like anthro- poid (after Pilgrim); F. Dawn- man; G. Primitive man (after Schoetensack); H. Modern man (after Gregory). WER IMATES The figures on the rignt give tne estimated duration of time in millions of years since the beginning of each epoch. For details, see pp. xix, xx. 61 EriroMeE or THE Fosstt History or HuMAN AND PREHUMAN PRIMATES (Continued). Fig. 38. Molars of: A. Primitive tree-shrew; B. Primitive tree- shrew; C. Primitive lemuroid (after Matthew); D. Primi- tive lemuroid (after Mat- thew); E. Proto-anthropoid; F. Proto-anthropoid (E and F from stereoscopic photo- graphs by McGregor); G. @r Be ‘MIOCENE OLIGOCENE Proto-anthropoid; H. An- thropoid; I. Anthropoid; J. Dawn-man; K. Neanderthal man; L. Neanderthal man (H, I, J, K, L, from stereo- scopic photographs by Mc- Gregor); M. Modern man; N. Modern man. oe Os 22 4 13 Ga @ Bs 1 24 LOWER PRIMATES: hh hddliliddiiliidiifdidddlliddliifililgeTea For details, see pp. xx, xxi. 62 OUR ANCIENT RELATIVES evolution of the teeth, jaws, braincase, middle and inner ear, vertebral column, pelvis, hands and feet. Meanwhile Elliot Smith, Tilney, Hunter, Le Gros Clark and others have shown how the existing tree-shrews, lemurs, monkeys, apes and man pre- sent a progressive series in the evolution of the brain as a whole and of the various nuclei and centers controlling bodily functions and _ be- havior. Sir Arthur Keith and others have also traced step by step the structural adjustments in the diaphragm, abdomen and pelvic floor, as the originally horizontal body assumes a sitting po- sition or moves erect as in the gibbon and man. It is remarkable how completely the results of the students of the nervous system and of the anatomy of the viscera accord with studies on the evolution of the teeth, skull, limbs, ete., and on the classification and fossil history of the families and genera of Primates. Taken together, these results afford cumulative evidence for the conclusions that man still bears in his whole organization an indelible stamp of the 63 OUR FACE FROM FISH TO MAN tree-living habits of his remote primate ancestors and that these tree-living adaptations were overlaid by a later but.very extended series of adaptations for bipedal running on the ground. THE ALMOST HUMAN FACE APPEARS Doubtless many factors conditioned the pro- gressive enlargement and differentiation of the brain, which is so marked a characteristic of the whole Primate order, but perhaps the leading factor was the correlated use of eyes and hands and at first, feet, not only in locomotion but in the seizure and manipulation of food. And no doubt the habit of sitting upright also tended to free the hands for the examination of nearby objects, while the habit of climbing in an erect posture, as in the gibbon, finally gave rise to the almost human face of the anthropoid apes, as will pres- ently be shown. We do not yet know the exact time and place in which certain advanced primates began to take on specifically human characters, although there is much evidence at hand indicating that the time was not much ‘earlier than the Lower Miocene, and the place somewhere within the known area 64 Fic. 39. One or Our Nearest Livinc REevatives. FEMALE CHIMPANZEE AND YOUNG. (From ‘‘ Almost Human,” by R. M. Yerkes. Courtesy of the author and The Century Company). For details see p. xxi. Fic. 40. Maur anp FemMaALe CHIMPANZEES. (After J. A. Allen, from photographs by Herbert Lang.) OUR ANCIENT RELATIVES of the anthropoid stock at that time, which ranged from India to Spain. But Darwin’s conclusion that mankind represents a peculiar and specialized offshoot from the anthropomorphous subgroup of Old World primates, after three-quarters of a century of anatomical and paleontological re- search, is backed by a mountain of evidence. The female chimpanzee in the side view of the skull stands nearer in resemblance to man than it does to the primitive Eocene primate Notharctus. The chimpanzee in fact has acquired all the “basic patents”’ in skull architecture which were prerequisite for the final development of the human skull. The most eminent students of the brains of animals and men conclude that partly as a result of the necessity for keen sight in actively climbing animals, the eyes in primates (Fig. 35) moved around from the sides of the face, where they are in the lower vertebrates, and were brought to the front, where in the anthropoid apes they finally acquired biconjugate movements and stereoscopic vision. In the anthropoid apes, moreover, the sense of smell no longer dominates the brain system as it did in lower vertebrates, but its reign 65 OUR FACE FROM FISH TO MAN is usurped by the sense of sight. Concomitantly, the brain of the chimpanzee has increased greatly so that the braincase is distinctly subhuman in appearance. The erect position assumed by apes that climb so much by means of their arms as do the anthropoids has conditioned the bending downward of the face upon the braincase (Fig. 36). Everyone recognizes in the chimpanzee (Fig. 40) a gross caricature of the human face, in which the mouth and lips are absurdly large and the nose flat with little or no bridge. But from the anthro- poid viewpoint the human face may well appear equally grotesque, with its weak little mouth, exposed lips and unpleasantly protruding nose. Possibly the common ancestor of man and apes would be shocked by each of his descendants. But allowing for much divergent evolution in the end forms, what makes men and anthropoids so much more like each other in fundamental features of the face than either is to the oldest forerunners of the entire order, long antedating their nearer common ancestor? First, let us set down in parallel columns a few of these resemblances’ and differences. 66 Fic. 41. Lerr Lower Cueex Treetu or Fosstu AntHRoporD (B) FROM InprA AND Fosstt Primitive Man (A) rrom Prurpown, ENGLAND. (A, from photograph by J. H. McGregor; B, after Gregory and Hellman). The lower molars of the Piltdown jaw, although much ground down by wear, show the pure “Dryopithecus pattern” characteristic of recent and fossil apes. For details see p. xxi. OUR ANCIENT RELATIVES Muzzle and snout Mouth Tongue Lips Number of premolars, upper Number of premolars, lower Form of first and sec- ond upper molars Cusps of lower molars Lower jaw Opposite halves of lower jaw Eyes Bony partition behind eye orbits Premaxilla and max- illa Occipital condyles EARLIER PRIMATES (Cf. Figs. 33, 34A) 35A, 36A) Long, pointed, extend- ed chiefly forward Narrow, elongate Narrow Not protrusile Four Four Triangular, three main cusps Sharp Long, slender Separate Look outward and forward Barely begun Separate On rear of brain base ANTHROPOIDS AND PRIMITIVE MAN (Cf. Figs. 35E, F; 42, 43, 44) Short, wide, extended chiefly downward Wide, short Broad Strongly protrusile Two Two Quadrangular, four main cusps Low, blunt Short, deep Fused in front Look forward, binocu- lar, biconjugate Complete Fused in adult More on under side of brain base This comparison could be greatly extended by the inclusion of technical anatomical details, but is sufficient to indicate the main features of the bony face in which man and the anthropoids have In the earliest primates the characters mentioned above advanced beyond the primitive primates. are already adapted to a diet of insects and vege- 67 OUR FACE FROM FISH TO MAN tation and to a horizontal position of the vertebral column; the anthropoids, on the other hand, are chiefly frugivorous and their vertebral column is more or less erect. Fic. 42. Fosstr ANTHROPOID AND HuMAN SKULLS. A. Australopithecus, a young extinct anthropoid (after Dart); B. Eoanthropus (after A. S. Woodward and J. H. McGregor); C. Pithecanthropus erectus (after Dubois); D. Neanderthal (after Boule); E. Talgai (after S. A. Smith); F. Rhodesian (after A. S. Woodward); G. Cro-Magnon (after Verneau). In the female and young skulls the brow ridges are less projecting or entirely lacking. For details, see pp. xxi, xxii. 68 OUR ANCIENT RELATIVES The close anatomical relationship of man to the anthropoids, together with the fundamental iden- Fic. 43. ANTHROPOID AND Human Sxuuts. Tor VIEw. A. Chimpanzee (after Boule); B. Pithecanthropus (after Dubois); C. Neanderthal (after Boule); D. Cro-Magnon (after Boule). tity in the molar patterns (Fig. 41) of the most ancient fossil men to those of still older anthro- poids, indicates that man has been derived from frugivorous pro-anthropoids and that after man ~ 69 OUR FACE FROM FISH TO MAN left or had been driven forth from the ancient forests, his omnivorous-carnivorous habits were developed during the age-long and bitter struggle for life on the plains. Thus the gentle pro- anthropoids, quiet feeders on the abundant fruits of the forest, introduced a long periud of peace- ful development in the strenuous upward struggle. \ } } | Li Pa Fic. 44. ANTHROPOID AND HuMAN SKULLS (AFTER BOULE). A. Chimpanzee; B. Neanderthal; C. Modern European. This peace was rudely broken when from some zoological Garden of Eden, that is, from the center of post-anthropoid evolution, the ancestral horde of savage pro-hominids were turned out on the plains to devastate the world. AT LAST THE “‘PERFECT”’ FACE As yet there is an immense hiatus in the paleeon- tological history of man, covering at least several million years in the Pliocene epoch. All known 70 aT ar NYS SS < + aw" a Tae NNN Vy. \ Fic. 45. Comparative VIEWS OF SECTIONED LOWER JAws. A. Dryopithecus (after Gregory and Hellman); B. Chimpanzee; C. Piltdown (after A. S. Woodward); D. Heidelberg (after Schoeten- sack); E. Ehringsdorf (after Virchow); F. Neanderthal (after Weinert); G. Cro-Magnon (after Verneau). 71 OUR FACE FROM FISH TO MAN early human fossils are unquestionably human in one way or another—even including the famous Pithecanthropus, which zealous anti-evolutionists stoutly refuse to admit to the human family. But it is also noteworthy that each of these earliest human relics is ape-like in a different way. The Piltdown lower jaw (Fig. 41) and teeth are extra- ordinarily ape-like; the Pithecanthropus skull (Fig. 42C) is ape-like both in its projecting brow ridges and in certain features of the occiput, while the braincast, according to all expert analysis, is far inferior in certain respects to that of Homo sapiens; the Heidelberg jaw (Fig. 45D) has a receding chin and the Mousterian skull has many primitive ape- like details in the teeth (Fig. 45F) that are usually lost in Homo sapiens. The Rhodesian skull (Fig. 42F) shows remarkably gorilla-like details of the bony lower border of the nose, indicating a very low form of nasal cartilages and nostrils; the Talgai (Australia) skull is a proto-Australoid type with extreme prognathism (Fig. 42E). The Australom- thecus skull (Fig. 42A) is that of a young anthro- poid with an exceptionally well developed brain (Dart, Sollas, Broom). While it may be nearer to the chimpanzee than to man, its brain, skull 72 Fic. 46. Tue “Atmost Human” SkuLut or AUSTRALOPITHECUS, A YOUNG Fossin ANTHROPOID (AFTER Dart). Fic. 47. Restoration or tHe Heap or THE YOUNG AUSTRALOPITHECUS. (After a drawing by Forrestier made under the direction of Elliot Smith.) OUR ANCIENT RELATIVES and teeth tend to bridge the gap between the high- est apes and the lowest men. Such were the last fleeting souvenirs of the pre- human stage, surviving millions of years after the first separation of the human and great ape fam- ilies. They represent various degrees of approxi- mation toward the modernized type of face, from the almost ape-like lower jaw of Piltdown to the highbred old man of Cro-Magnon (Fig. 42G). Thus the scant evidence suggests that even in Lower Pleistocene times there were already several different types of mankind, some (such as Pilt- down) more progressive or less ape-like in the shape of the forehead, while more conservative in the form of the dentition and jaw, others (Pithe- canthropus) with a lower form of forehead and not improbably a more progressive form of Jaw. Whether these represent individual, racial or specific difference is not fully demonstrated; in any case they suggest that within the family of man- kind there was a remarkably wide range of varia- bility in facial characters, as there still is. The profound agreement between mankind and the anthropoid group in anatomical characteristics and in physiological reactions and to a certain 73 OUR FACE FROM FISH TO MAN extent in basic mental traits (Yerkes, Koehler) all sufficiently establish the fact that at one time the human and anthropoid groups converged back- ward to a common source. It is also the plain teaching of comparative anatomy that the modern- ized white human face with its small mouth, weak jaws, reduced dentition, projecting chin, delicate projecting nose and pale skin, has changed far more from the primitive man-anthropoid starting- point than has the face of a young chimpanzee, with huge mouth, strong teeth, receding chin and flat nose. Professor Osborn holds that the separa- tion of man and apes from the primitive anthro- poid stock began as far back as the Lower Oligo- cene epoch, possibly some thirty-five million years ago, while the present writer is inclined to date this event from the next higher epoch, namely the Lower Miocene, possibly nineteen million years ago.* Whichever date, if either, may eventually prove to be the true one, the fact remains that in its present form the modernized human face is swt « These figures are according to the tentative estimates of the geo- logical epochs worked out by Barrell by the “radium emanation” method, based on the rate of disintegration of radioactive ores from different geological horizons. 74 OUR ANCIENT RELATIVES generis, just as the face of any other species of mammal is unique in its specific attributes. But there are thousands of good scientific reasons for accepting as a fact the evolution of man from lower mammals, there is a convincing chain of known forms in the long series from fish to man; and even in civilized man the human face is most obviously related rather closely to that of the anthropoids; therefore only the most confirmed mystic by preference will insist that the evolution of the human face is a “mystery.” It is true that every event of the kind abounds in mystery, since no matter how fully we can describe by what stages it happens, we uncover infinitely ramifying problems whenever we attempt to isolate the causal factors. Undoubtedly when primitive man left the forests and came out on the plains to live by hunting there was a change in food, a change from a frugivorous to at least a partly carnivorous diet, there was a change of locomotion from erect tree-climbing (brachiation) to bipedal running on the plains; speech arose and the brain grew so large that it grew faster than the face; the period of individual growth and development was greatly extended; all 75 OUR FACE FROM FISH TO MAN the system of the ductless glands which has so profound an effect upon growth and development was affected in innumerable ways and differently in different individuals and races. Thus we begin to sense the complexity of the factors influencing the emergence of the typical human face from a primitive anthropoid type. Whatever the causes may have been, the evi- dence indicates that, starting with a face not dis- similar to that of an immature female chimpanzee (Fig. 40B), the forehead rapidly became larger, the incisor teeth became less inclined, more vertical and smaller in size, the canine teeth diminished in size and in such a way that the tip of the lower one finally passed behind the front edge of the upper canine; the premolars and molars also decreased in fore and aft diameter. In addition to the reduction and backward displacement of the teeth there was a positive outgrowth of the bony chin, which possibly on account of the early development of the tongue could not retreat fur- ther backward. ‘The later stages of this process may be reconstructed by comparing the faces of different races, from the projecting muzzles, very large mouth, broad flat nose and retreating chin 76 OUR ANCIENT RELATIVES of some of the Tasmanians (Fig. 10, Frontispiece) to the narrow, forwardly-projecting, pointed nose and pointed chin of the Alpine, European type (Fig. 11 Frontispiece). 77 NTI AY ANA I ane ea Fic. 48. Evoiution or THE Hv- MAN SKULL: TEN STRUCTURAL STAGES. I. Lobe-finned fish, Devonian age (after Traquair, Watson, Bry- ant). II. Primitive amphibian, Lower Carboniferous (after Wat- son). III. Primitive cotylosau- rian reptile, Permo-Carboniferous (after Broili, Williston, Watson). IV. Primitive theromorph reptile, Permo-Carboniferous (after Willis- ton). V. Gorgonopsian_ reptile, Permian (after Broom). VI. Primitive cynodont reptile, Trias- sic (after Broom, Haughton). VII. Primitive marsupial, Upper Cre- taceous (after Matthew) VIII. Primitive primate, Eocene (after Gregory). IX. Anthropoid (female chimpanzee), Recent. X. Man, Recent. For details, see pp. xxii, xxiii. 78 MY Uy oy Hil 8 l] LN | oy aeeeiaas oS lp) CO tr o) ~ Minny Wp rnca ad as ry) SC > ". DO ii, a MI ar iy ] Wp ”) I eS S Sa ij Mr I ..\4 aay) » UR NTH) LT W) y oN D Mh My il : m np 5 / Hsia tavagt omy yi ng . he . My Wi if 79 Mi Yi, co; My, UM Gf Hy i a) VL? aay ik y if) Yyjjjm yyy MMMM CY . — . ssovnith Si NY y YY Y Hi iff My MU WY 7 Ny, < oe Why ee” q YP LEED Wy OHM MLL CALE Fiae. 50. Evouution or THE Human JAw-BongEs. Same series as in Fig. 49. *For details, see p. xxiii. ay, oy Up iff Ys LL - 80 2 jj fff i iri Mi: Nintuee, Y] } Say Uf UD Op». YD MY ) IN Uf) lp ITAL fii i) H} y) Y] iff mT, PUL My Ll Py) meyiomy , LY “YY Yo pty yy f Fig. 51. Evoxnution or THE Cir- CUMORBITAL BONES. Same series as in Fig. 49. For details, see p. xxiii. 81 OM TT ij:"un z ay ap eo >. Lee Wig = ay Sy Vil fone my DL iy Tam , acme rare Le oe el al G Mp Sy Fie. 52. Evo.,ution or THE Bones Breuinp THE JAws. Same series as in Fig. 49. Figures 48-52 give excellent examples of ‘‘ Wil- liston’s law” of the progressive elimi- nation of skull elements in passing from fish to man. Xx For details, see pp. xxiii, xxiv. 82 PART II CONCISE HISTORY OF OUR BEST FEATURES Tur Bony FRAMEWORK OF THE Gop-LIkE Mask To review at this point the history of the bony framework of the face, we note that the human skull as a whole is a complex consisting of a chon- drocranium, or inner skull, which is preformed in cartilage, and an outer shell of dermal bones, formed in membrane. The chondrocranium com- prises the base of the skull, the sphenoid bone and the olfactory and otic capsules. The outer, or dermocranium, comprises: (a) the roofing bones (nasals, frontals, parietals, and the membranous part of the supraoccipital) ; (b) the orbital elements (lacrymal, jugal, or malar); (c) the squamous part of the temporal bone; (e) the maxillary elements (upper and lower jaw bones); (f) the palatal bone and the internal pterygoid plate of the sphenoid; (g) the vomer. The illustrations submitted herewith (Figs. 83 OUR FACE FROM FISH TO MAN 48-53) set forth a few of the facts which have convinced modern anatomists that man, like other mammals, was not created at one stroke, but that he reached his present condition by gradual stages of modification, which, thanks to the unremitting labors of many paleontologists and anatomists, now appear to be fairly well understood. None of these stages is hypothetical; they are either known fossil forms or are the surviving and little-modified descendants of known fossil forms. From the imperfect nature of the fossil record we can never expect to recover the infinite number of links in the direct line of ancestry of man or of any other mammal. The record affords us only successive structural stages that are more or less nearly related to the main line of ascent from fish to man. The story told in these illustrations has not been invented by the writer. It has slowly revealed itself as the paleontologists and anatomists of a century past have gradually unearthed it. During the past fifteen years great progress has been made all along the line of stages I to X, either in the discovery of hitherto unknown or little-known forms, or in the determination of the sutural 84 Wn Ly Wy Y "a O-s a> Pp 6 8 2.2'5 ne Ss Mw | cas OT t SAY eee 22.8 tyemem GM ores Paks vg | Nee ty a0 or nis Yo B.A gt fat oy Oe 8-1 9 28 5 SE a2eped HoOogo a ) i= OUsgds oog -O°990 aga Broa ee cy o> ee “=O oO Ba48 gd. -wHkS ae 3 + sacl cD) — 2 = 60 — OSes Beare so SRO ee Bey eae aseoq aS ‘BE 3.8 Fixes Pa a woTs PSS ie qd apwH oa Sed ~S5 808 Se 2 os Sook = Ay El Rae Oo SRM AOm sg oh 4 BO LES og 48.8 5 Fs. .& 28 2.25 any Sac Sacto qg> en Raia Am 8 8 ‘ ray BRoS & GOO. 1% 5 tg ask. Sane s Sis recs eases meX2a0 8 2S oa, ) of pas GOR Bon, od oPsoR Ooporo Sa 5 ag RESTS Ag a mi Px O'S ares e os eM OUR FACE FROM FISH TO MAN limits of the individual bones, or in the vital problems of determining the systematic relation- ships of each of the forms figured and of the groups that they represent. Recent palzeontolo- gists who have contributed especially to these subjects include D. M. S. Watson (in connection with Stages I, II, ITI, V, VI), Bryant (in connec- tion with Stage I), Williston (in connection with Stages III, IV), Broili (in connection with Stage III), Broom (in connection with Stages V, VI), Haughton (in connection with Stage VI), Matthew (in connection with Stage VII), Gregory (in con- nection with Stages VIII, IX). The drawings, like most of the others in this book, were skilfully executed by Mrs. Helen Ziska, working under the constant advice and supervision of the author. For whatever errors the figures may still bear, after many appeals to the original data, the writer alone therefore must be held responsible. To recapitulate, the outstanding changes in the lateral view of the skull from fish to man appear to have been as follows: Of the bones on the roof of the skull (Fig. 49), namely the nasals, frontals, parietals, interparietals (or dermo-supraoccipitals) and tabulars, only the 86 OUR BEST FEATURES last disappear entirely in the mammals. As the brain enlarges these roofing bones are lifted into greater prominence, the frontals, parietals, inter- parietals and occipitals becoming the dominant elements in the great vault of the human skull. The superior maxillary bone (Fig. 50) begins as a slender, vertically shallow element, but by the time of the early mammal-like reptiles (Fig. 50 V) it has extended dorsally and gained contact with the nasals. In the mammals (Fig. 50 VII-X) its dominance is still more pronounced; one fork reaches the frontals while another fork finally separates the lacrymal from the jugal and the whole bone becomes shortened antero-horizontally and deepened vertically. In the anthropoids and man the premaxille early unite with the maxille. The inferior maxillary (dentary) at first is confined to the anterior half of the mandible. In the higher mammal-like reptiles it becomes dom- inant, the post-dentary elements retreating before it. In the earliest mammals the ascending ramus of the dentary effects a new contact with the squamosal, the temporo-mandibular articulation, which is transmitted without further essential modification to man. 87 OUR FACE FROM FISH TO MAN Of the bones around the eye (Fig. 51), originally five in number, three (the prefrontal, postfrontal, postorbital) are eliminated by the time of the earliest mammals, so that man inherits only two of the original five, namely the lacrymal and the jugal or malar. The temporo-mandibular series (Fig. 52), orig- inally including eight bones (the intertemporal, supratemporal, squamosal, quadrato-jugal, sur- angular, angular postsplenial, splenial), suffers gradual reduction, until in the earliest mammals, as in man, only the squamosal remains, at least in the lateral view of the skull. In the mammals the squamosal has fused with the enlarged periotic mass and in the anthropoids and man the tym- panic is added, the whole complex forming the temporal bone. At every successive stage of evolution advances in skull structure were dependent upon improve- ments in the brain itself, upon shiftings and enlargements of the parts containing the sense organs, upon modifications of the jaws and teeth, accompanying or accompanied by changes of habits. The skull in turn is closely integrated with both the active and the passive elements of 88 a OUR BEST FEATURES the locomotor apparatus, a topic which will be developed elsewhere. To each of the stages described above man owes certain ‘“‘basic patents,’ or adaptive improve- ments which have been of critical importance in his survival. Thus to certain far-off Devonian air-breathing fishes man owes the general ground- plan of the vertebrate skull, the combination of primary “‘gill-arch”’ jaws with sheathing or outer jaws, and each and every one of the twenty-eight normal skull bones which he still retains. Next, he is indebted to the first amphibians for partially solving the innumerable problems caused by emergence from the water. These old pioneers cast off the whole series of bones that covered the branchial chamber and made for themselves an ear-drum out of the skin around the notch where the opercular was formerly located. The early reptiles safeguarded most of the inheritance from their semi-aquatic ancestors, dropping only the inter- and supratemporals. To the first of the mammal-like series man owes the beginnings of his temporal fossa and zygomatic arch, and the dominance of the superior maxilla. From the higher mammal-like reptiles he has inherited the 89 OUR FACE FROM FISH TO MAN further development of the temporal fossa and especially the dominance of the inferior maxillary or dentary bone of the lower jaw. To these progressive pro-mammals man can render thanks for the differentiation of his dentition into incisors, canines, premolars and molars, and apparently he can also thank them for the reduction of the numerous successional teeth to two sets, corre- sponding to the milk teeth and the permanent set. The earliest mammals invented one of the most useful features of man’s skull by eliminating from the masticatory apparatus all the elements lying behind the dentary and by establishing the temporo-mandibular joint. They also cast off the reptilian prefrontal, postfrontal and postorbital bones and cleared the way for the final simplifica- tion of the bony scaffolding of the face. To the earliest primates, well schooled in arboreal life, man owes the first steps in the glorification of the eyes, which become increasingly dominant. These still lowly but thrifty forebears made good the loss of the reptilian postorbital bar by elaborating a new one from conjoining pro- cesses from the frontal and jugal (or malar) bones. But still greater was our debt to the arboreal 90 OUR BEST FEATURES pro-anthropoids, those intelligent beings who elected to develop sight at the expense of smell. These skilled acrobats, moving in a_ vertical position, met and solved a new series of problems connected with the turning downward of the skull upon the upright column. They also made the first notable attempts to shorten and deepen the face and even took a long step toward enlarg- ing the brain and brain chamber. Starting with these and many like advantages gained during a long training in arboreal life, it was the task of our relatively nearer precursors (beginning possibly in Miocene times, or earlier) to re-adapt all these arboreal adaptations for a life on the ground and to take the final steps upward that have brought humanity to its present levels of intelligence. Wholly ignorant of the facts, the ancient Jewish priests indulged themselves in the fancy that man was made in the image of God; but modern science shows that the god-like mask which is the human face is made out of the same elements as in the gorilla; and that in both ape and man the bony framework of the face is composed of strictly homologous elements, inherited from a long line of lower vertebrates. 91 OUR FACE FROM FISH TO MAN Fisu-Trars AND Faces THE FIRST MOUTHS From air-breathing fish to man the general course of evolution seems clear enough, at least in its broad outlines. But when we inquire whence myomere Om Sm > Ih Im, SCXGLARAS Spinaltord notochord Citiatea. groove Fic. 54. ANatomy oF THE LANCELET, THE Most Primitive Livine CHORDATE ANIMAL (AFTER DELAGE AND H&ROUARD). A. Entire animal, seen as a semi-transparent object; B. Longitudinal section. For details, see p. xxiv. came the fish, the evidence while extensive is somewhat ambiguous and there is room for sharp differences of opinion. On the one hand, there is Professor Patten, who derives the whole vertebrate series from very ancient jointed animals remotely allied to the modern scorpions and Limulus; on the other hand, there are the more orthodox 92 | } q OUR BEST FEATURES zoologists, who infer that the greatly simplified form Amphiorus (Fig. 54), together with all the vertebrates, represent offshoots of some still undis- covered stock that also gave rise to the acorn- worms (Balanoglossus), the starfishes and certain other peculiar groups. According to this view, Fig. 55. Larva or EcuinoprerMs: SEeA-cucUMBER (A), STARFISH (B) AND OF THE “ACORN-WORM” (AFTER DELAGE AND HEROUVARD). For details, see p. xxv. the common ancestors of all these diversified groups were exceedingly simplified, free-swimming, marine organisms, consisting chiefly of a digestive tube bent at a right angle and enclosed in a thin balloon-like tissue, more or less folded into plaits and provided with strips of cilia, by the lashing of which the floating bag moved slowly through the water. Such forms (Fig. 55) are found living today as the larve or young stages of starfishes, 93 A OUR FACE FROM FISH TO MAN sea-cucumbers, and also of the acorn-worm Balan- oglossus. 'The mouth of these forms is the original mouth of the primitive gut or digestive tract. There is evidence from embryology that the mouth of the vertebrates is a compound structure Sspinaleara a AQUI i Sey 2- lop PEI C7 $e: ro\ mr Fic. 56. Inner ann OvtEeR Moura Poucurs In Empryo VERTE- BRATES: LARVAL LAamprey (A) (AFTER Minot); Empryo Rassit (B) (arrer MIsaAcovics). For details, see p. xxv. formed from the union of a down-pocketing of the outer layer or ectoderm, meeting a pouch growing out from the primitive gut. These inner and outer mouth pouches in the early embryos of lampreys, sharks and higher vertebrates, are similar to the inner and outer pouches that give rise to the gill openings, with which indeed they are supposed to be homologous. Moreover Stensi6 has recently shown that in the cephalaspid 94 OUR BEST FEATURES ostracoderms (Fig. 57) the mouth cavity was in series with the cavities of the gill openings and was probably homologous with them. The predecessors of the vertebrates probably fed upon small organisms and organic matter, B. ‘ i Ht >} Ma Hl Ih Hl ING Ih I, 1] , Fig. 57. AtTremMpteD REesTorATIONS OF THE MovutsH AnpD GILL REGION or Two CEPHALASPID OSTRACODERMS BY STENSIO. For details, see p. xxv. which were scooped into the mouth cavity and may have been passed along to the stomach by the lashing of cilia located in a groove, as in the living Amphioxus (Fig. 54). This method of ingestion by means of cilia may also have been practised by some of the ostra- coderms, the earliest known forerunners of the 95 OUR FACE FROM FISH TO MAN vertebrates (Figs. 4, 57). Such food habits would seem reasonable both for those ostracoderms, like Pteraspis (Fig. 4D), which had narrow mouths placed below a long rostrum and therefore adapted for feeding in the mud, and for those like Tremat- aspis (Fig. 4B, C) in which the fore part of the body was flattened into a broad rounded shovel and the mouth was a wide slit-like opening at the = « eee Oe Zae 2 SV XTITKKSE: BEE Fig. 58. Swirt-movinc OstRACODERM FROM THE SILURIAN or Norway (AFTER KIAER). For details, see p. xxv. front border of the head. In Cephalaspis (Fig. 57B) also the mouth appears to have been in series with the gill-arches. But there were still other ostracoderms of the order Anaspida (Fig. 4A), in which the body-form seems adapted for swift movement through the water and in which the mouth, while not too large to be powerful, was strengthened by a bony strip with a knob on its front end. Such ostracoderms may have already embarked on the career of 96 OUR BEST FEATURES piracy which seems to have characterized the more remote ancestors of man for countless ages. But up to this point in their evolution true teeth had not been attained by the early predecessors of the vertebrates. sninalcora nostril brain nolochord cavity B gillsand gillstits anlesline Fic. 59. A Moprern DESCENDANT OF THE OsTRACODERMS. A. Adult lamprey (after Jordan and Evermann); B. Longitudinal section of larval lamprey, enlarged (after Goodrich). THE BEGINNINGS OF TEETH The ostracoderms as a whole may be transitional between the method of “ciliary ingestion” and the devouring of living flesh by the existing cyclostomes (lampreys, hags), which Stensié has 97 OUR FACE FROM FISH TO MAN shown to be the highly specialized, eel-like, and in some respects degenerate derivatives of the ostracoderms of Silurian times. Even today (Fig. 59) in the early larval lamprey (Ammocoetes stage) the pharynx is provided with a prominent “ciliated groove,” which (like that of Amphiorus) appears to be reminiscent of the earlier days of feeding on microscopic organisms; the adult lamprey, on the other hand, is a cruel pirate, rasping off chunks of flesh from the sides of helpless fishes and occa- sionally eating its way, it is said, into their interiors, finally reducing them to floating shells. The lampreys and their allies are enabled to carry on their nefarious business by means of thorny teeth, set in concentri¢ rows about the mouth and flanking a protrusile rasp, which is likewise covered with horny teeth and can be drawn back and forth like the rasp of a whelk. The teeth of the lampreys (Fig. 60A) are of extraordinary interest, since they have always been regarded as representing a very early stage in the evolution of the teeth of vertebrates. Each tooth consists of a thick, horny, epithelial thorn with a pulp cavity within, which is ready to grow another thorn as soon as the outer one is broken 98 OUR BEST FEATURES Tirst hornylooth Cpiaerms Lenelth tooth GocdOOr * Ws } <4 soasf RY N OOS y r > 0 = GOTTA eS Rand pepoceees wSS aD . Leys) ty) oe r Ss 5 x a : OS 7 SS Say OSG” nutre. ive papilla Or Bevrnis y - _— / ww * Se & “), ¢ Ga Fic. 60. DrveLopmeNT or TEETH IN LAMPREY (A) AND SHARK (B, C, D). (AFTER GoopRICH.) For details, see p. XXvi. 99 OUR FACE FROM FISH TO MAN off or shed. Nevertheless the teeth of the higher vertebrates probably arose not from horny epi- thelial teeth like those of the modern lampreys, but from enamel-covered shagreen denticles such as covered the whole body of Lanarkia, one of the Scotch Silurian ostracoderms. In the sharks (Fig. 60B, C, D) each little shagreen denticle on the surface of the skin consists of a little cone in which a porcelain-like layer of “enamel”’ is laid down between the epithelial covering and the pulp cavity. These shagreen denticles, together with the stratified bony deposits in the deepest layers of skin, gave rise not only to the teeth of higher vertebrates but also to the enamel-covered bony plates that cover the braincase, the bony tooth-bearing plates that cover the primary cartilaginous jaws and the bony tooth-bearing plates on the roof of the mouth, both in the air- breathing, lobe-finned fishes and in their successors, the earliest amphibians. These enamel-covered plates were also homolo- gous with the bony ganoid scales on the surface of the body. Thus we are again reminded of the remarkable potentialities of the many-layered skin in the 100 OUR BEST FEATURES ancestors of the vertebrates, since it gave rise in different groups to horny thorns, to shagreen denticles, to true stratified bony scales, to enamel- covered skull plates, as well as to many different kinds of sense organs. Nor can it be too often pointed out that the whole organization of primitive vertebrates was adapted for the pursuit and capture of living prey, that sharp teeth were made from the shagreen of the skin, first for holding and then for cutting living prey, that in every geological age until we reach the primitive anthropoid stock of relatively recent times, the herbivorous forms, derived from the more primitive carnivores, acquired various types of specialized teeth which could never have given rise to the higher carnivorous types. Any hypothesis that would derive the earlier carniv- orous vertebrates from herbivorous predecessors would be definitely contradicted by all the avail- able evidence afforded by a comparative study of the brain, sense organs, the locomotor apparatus and the digestive system. After a century of intensive research we can only speculate, almost idly, as to what may have been the mode of origin of the mouth, jaws and 101 OUR FACE FROM FISH TO MAN teeth below the ostracoderm grade of evolution. But when we reach the grade of evolution repre- sented by the shark, we find that the shark stands unquestionably nearer to man in the construction of its gaws and teeth than it does to any known group of invertebrates; while between shark and man many intermediate conditions of the mouth are definitely known. THE PRIMARY JAWS The gill pouches of fishes and of the embryos of higher vertebrates, including man, are supported by cartilaginous bars (Figs. 7, 8), the so-called “visceral arches,’ and the mouth pouches of sharks and embryo vertebrates are likewise sup- ported by cartilaginous bars, the oral cartilages, which have every appearance of belonging in series with the gill arches. The primary upper jaw cartilages, one on either side, are called the palatoquadrate cartilages, while the primary lower jaw cartilages are called Meckel’s cartilages, or the by mandible. The “labial cartilages” in front of the jaws (Figs. 7, 8) are possible remnants of at least one ‘‘premandibular”’ arch. In the predecessors of the sharks, we may infer, 102 temporal y--opressor eee ed , . S q Y\ % Y i mandi duke plerygoia Femporal “evatormaxillae su (atte ramet 2) rot a EET Hees WED TE BE masseter (add. mandi) mandtibulce Fic. 61. Evo.ution or tHe JAw Muscuies From Fisu to Man. I. Shark (data from Allis). II. Lobe-finned ganoid (after L. A. Adams). III. Primitive amphibian (after L. A. Adams). Restora- tion. IV. Primitive mammal-like reptile (skull mainly from Broom). Restoration. V. Advanced mammal-like reptile (after L. A. Adams). Restoration. VI. Primitive marsupial (after L. A. Adams). VII. Primitive primate. VIII. Chimpanzee. IX. Modern man. For details, see p. xxvi. 103 OUR FACE FROM FISH TO MAN none of these “visceral arches’’ (labial cartilages, jaws or gill arches) were connected with the brain- case except by connective tissue and as the living prey was presumably small there was no need of special bracing for these arches. But as the race grew larger the size of the prey likewise increased and convulsive swallowing efforts were made by the fish to force the prey past the region of the gill pouches down into the stomach. At the same time the contractile muscles around the whole branchial series grew stronger, those attached to the future jaw arches increased faster than their fellows and so did the future jaws themselves. In this way the jaw muscles of the shark and of higher vertebrates (Fig. 61) were apparently derived by enlargement from muscles correspond- ing to the constrictor muscles of the gill arches. For a long time the primary upper jaw was suspended from the skull mainly through its attachment to the second or hyoid arch (Fig. 62A) but in the amphibians and higher vertebrates the primary upper jaw itself becomes attached to the skull (Fig. 62, B, C). When large tooth-bearing bony plates came to sheath and cover over the primary upper and lower jaws they gradually 104 primary Upper Jaur SZ (Paro. guaarate, EN A primary lowerjair teckels cartilage) "Yd Gl arches — rN \\X \ ~>—=~ SSS. Sa Py A~ZE4 ‘4 ‘ ‘ \ Fic. 62. Mrtnops or ATTACHMENT OF THE Primary Upper Jaw to TRE UNDER SIDE OF THE SKULL. In C the bony mask covering the temporal region is cut through and a part of it removed to show the primary upper jaw and its relations to the braincase. For details, see pp. XXvi, xxvii. 105 OUR FACE FROM FISH TO MAN supplanted them, at least in the tooth-bearing regions. In mammals (including man) clear traces of the primary upper jaw may be found in early embryonic stages of development (see Keith, Human Embryology and Morphology, 1921, pages 138, 148, 172). THE RISE OF THE SECONDARY JAWS AND THEIR TEETH Up to the present time we have been dealing with the origin and early evolution of the primary upper and lower jaws, but in the higher vertebrates, including man, these primary jaws are completely overshadowed and masked by the secondary jaws. In the sharks the secondary jaws are represented merely by the skin that is wrapped around the primary jaws, or palatoquadrate and Meckel’s cartilage, both on the outside and on the inside of the mouth. In the sharks this skin has no bony base but in the higher fishes and early amphibians the primary upper and lower jaws are covered with many-layered bony plates originally provided with a porcelain-like surface of “ganoine”’ and usually bearing numerous teeth. In the early lobe-finned, air-breathing fishes (Figs. 11, 12) 106 OUR BEST FEATURES these plates are of exactly the same nature as the roof-bones of the skull and the scales on the body. Thus arises the hard “facial mask” so often referred to in the preceding pages. As used in this book the term “secondary jaws”’ is limited to the tooth-bearing plates covering the external borders of the primary upper and lower jaws. There are three of these elements on each side of the head throughout the series (Fig. 50) from fish to man and their amazing constancy is an item of evidence of the unity of plan and origin of all the higher vertebrates. The first of these secondary jaw elements is the premazilla, one on each side of the mid-line, at the front end of the jaw; this is followed by the mazilla, one on each side behind the premaxille. When we compare the under side of the skull (Fig. 63, I, II) of one of the fossil lobe-finned (crossopt) ganoids of the Devonian with that of one of the early amphibians of the Coal Measures, we can hardly doubt that the premaxilla and maxilla of the former are each completely homologous with the corresponding element in the latter. And from the earliest amphibian to man they can be traced in convincing detail (Figs. 50, 53). 107 OUR FACE FROM FISH TO MAN The third of the secondary jaw elements is the dentary bone, one on each side of the lower jaw. In the lobe-finned or crossopt fishes this bone, Ws IZ Fic. 63. Unper Sipe or THE SKULL or Devontan Fosstt Fisa (A) AND Primitive Fosstr AmpuHisiAn (B). (A arTeR BRYANT AND Watson; B arrerR Watson). The secondary upper jaws are on the margins; the primary upper jaws are largely covered by tooth-bearing plates of the primary palate. For details, see p. xxvii. while bearing a stout series of teeth, had not yet assumed the primacy it acquired in later types. We have already (pages 36-39) traced its progress in the mammal-like reptiles and have seen it encroach on the other membrane bones of the lower jaw until it finally secured a contact with the 108 OUR BEST FEATURES squamosal bone covering the side of the temporal part of the skull, by which time it had succeeded in crowding its fellows quite off the map. Meanwhile, how did the crossopts and early amphibians acquire the strong teeth with which they carried on their predatory lives? In the most primitive sharks (Fig. 5) the shagreen-bearing skin is rolled around over the upper and lower jaw cartilages and as the old teeth are broken off the new teeth are gradually pushed up into place on the edge of the jaws in a continuous succession. In the typical sharks the tooth-bearing roll of skin lies in a depression in the calcified cartilaginous primary upper and lower jaws, but the teeth are not separately connected with the jaws and when in use are tied in place only by the strong dental ligament attached to their bases. In the crossopts (lobe-finned fishes) of the Devonian period the primary upper jaw (palato- quadrate), now completely saturated with bone cells, is covered with bony dermal tracts bearing teeth, some very large and compressed, some small and conical. In front there is also a pair of tooth-bearing dermal plates, the prevomers, on either side of the mid-line. Likewise the secondary 109 OUR FACE FROM FISH TO MAN upper jaws, the premaxilla and maxilla, bear compressed conical teeth. The dentary plate of the lower jaw (Fig. 64) covering the outer side of the primary lower jaw or Meckel’s cartilage, bears a row of conical teeth which fit between the marginal teeth of the secondary upper jaw and the larger teeth on the dermal plates covering the primary upper jaw. Thus we have the teeth of the secondary upper jaw over-hanging or biting outside of those of the dentary or lower jaw, an arrangement that persists throughout the sub- sequent series upward to the primitive mammals, traces of it even being preserved in man. The coronoid bones, covering the inner side of the primary lower jaw, in the lobe-finned fish bear large teeth which doubtless sheared into the struggling prey and pressed it against the large teeth on the roof of the mouth. Thus neither the Meckel’s cartilage, or primary lower jaw, nor the palato- quadrate, or primary upper jaw, now have any direct relations with the teeth, which are supported entirely on their own bony plates, as they are in all higher vertebrates, including man. The pri- mary lower jaw from this point onward takes a subordinate part, except that its nearer (proximal) 110 Ws Se fa Oa Ss Ee ee STéCK, : — —— D Meth. sul point angi prearte VTeckels cartilage fe Sieg Fie. 64. Riccar Haur or tHe Lower Jaw or Lose-FINNED FisH (A, C) anp Primitive Fosstz Ampuisian (B, D), ann ReEcENT TurtTLE Emeryo (E). (A, C, arrer Watson; B, D, arrEer Wiuuiston; E, artER PARKER.) For details, see pp. xxvii, xxviii. 111 OUR FACE FROM FISH TO MAN end, after becoming ossified (after which it is called the articular bone) serves for the main articulation of the lower jaw with the primary upper jaw; this arrangement persists from the crossopt fishes up to the most advanced mammal- like reptiles, which are the immediate predecessors of the mammals. Each tooth of the above described fossil crossopt fishes consists essentially of an enlarged cone with an open pulp cavity, the sides of the cone being very deeply infolded toward the base, so that in cross-section the primary and secondary folds give rise to the characteristic labyrinthodont pattern (Fig. 18). The surface of the tooth is deeply covered with enamel-like ganoine, which is folded into the primary and secondary folds, and the interior consists of dense, stratified bone or dentine. The derm bone which bears the tooth is strongly attached to it and is folded into its sides along with the primary and secondary folds. This labyrinthodont mode of attachment of the teeth to the jaw bones is a far more primitive and important method than any of those commonly cited in textbooks on comparative dental anatomy, which usually describe only the either degenerate 112 OUR BEST FEATURES or highly specialized modes of attachment found in modern amphibians and reptiles, since it was the starting-point of the conditions found in the higher vertebrates, including man. To sum up then, the lobe-finned fishes exhibit a great advance upon the sharks toward the am- phibians and higher vertebrates in the following respects: (1) the primary upper and lower jaws are now covered with tooth-bearing bony plates, only the back part of the primary upper jaw (forming the quadrate bone) and of the primary lower jaw (forming the articular bone) being exposed and forming the articulation between the upper and lower jaws; (2) the secondary upper and lower jaw (premaxilla, maxilla, dentary) for the first time appear as ossified tooth-bearing plates, which may be compared directly with those of amphibians and higher vertebrates; (3) each tooth represents an enlarged denticle with the base infolded into the labyrinthodont pattern. It is fastened to the bone by the infolding of the latter into the labyrinthodont folds; (4) thus the upper and lower jaws as a whole are of complex construction, including a large number of distinct bony plates, some of which disappear as we pass 113 OUR FACE FROM FISH TO MAN to the higher vertebrates, but three of which (premaxilla, maxilla, dentary) persist even in man (Fig. 50). All these highly predatory adaptations were transmitted by heredity to the oldest known amphibians of the Coal Measures, which are at the very least rather close relatives if not actual descendants of the osteolepid crossopts. The chief advance in these oldest amphibians is the elimination (Fig. 17) of the whole series of plates connected with the opercular tract and consisting of the plates named operculum, suboperculum, interoperculum, preoperculum, and a series of small lateral gulars or branchiostegals. All these were sacrificed when the amphibians eliminated the internal gills in the adult stage. The loss of these plates not only constitutes a fine example of Williston’s law of the progressive reduction in the number of bony elements, as we pass from fish to man, but also serves to bring out the fact that evolution proceeds fully as much by the loss of superfluous parts as by the further differentiation of those that remain (Figs. 50, 52). Many of the amphibians adopted the easy method of lying in wait in the water for their prey, 114 OUR BEST FEATURES perhaps even with their mouths open, and then suddenly engulfing it in a living trap. Such a line of specialization leads often to wide flat skulls and very shallow, widely-bowed jaws set with rather small teeth on the margins and a few larger piercing teeth on the roof of the mouth, as in the great labyrinthodonts or stegocephalians of the Permian and Triassic periods. Others, in which the jaws became very long and narrow, actively swam in pursuit of fishes. But those amphibians (e.g. Fig. 48 II) which were destined to give rise to the line of ascent to man, avoiding both these extremes, had jaws of only moderate length and a skull of moderate width and considerable depth, especially toward the rear end. At first they retained the teeth on the roof of the mouth (Fig. 53, II-IV) but in the series of reptiles (Fig. 53, V) that finally culminated in the cynodonts (Fig. 53, VI) and probably in the mammals (Fig. 53, VII), the teeth on the roof of the mouth, that is, on the primary upper jaw, were eliminated and the marginal teeth on the secondary jaws acquired the typical dog-toothed or caniniform type of predatory animals that pursue their prey on land. From this condition there are intermediate stages 115 OUR FACE FROM FISH TO MAN to the essentially mammal-like dentition of the cynodonts (Fig. 50 VI), in which the adult denti- tion, as in man and other mammals, consists of incisors, canines, premolars and molars, and in which the dentition was apparently reduced to two sets corresponding to our milk and permanent teeth. Moreover, each tooth in the cynodonts was set in a distinct socket as in the mammals. Hence these reptiles had already traveled far on the long road from fish to man. We have followed some of the _ progressive changes in the jaws of these forms, in which the dentary bone finally became the predominant element and gained contact with the squamosal bone of the skull (Fig. 21), while the bones behind the dentary were reduced to slender proportions (Fig. 52). These changes, however they may have been initiated, were obviously associated with a great development of the temporal, masseter and pterygoid muscles of the jaws (Fig. 61), which have very strongly braced areas of origin and attachment. To the activity of the temporal muscle we apparently owe the first appearance of the temporal fossa (Fig. 48 IV) in the shell of bone that formerly roofed over the jaw muscles, while 116 OUR BEST FEATURES to the increase in size of the pterygoid muscles may safely be ascribed the pinching together of the opposite pterygoid bones and the development of a high bony crest on the mid-line of the base of the braincase (Fig. 53 V). Turning again to the teeth, we may summarize their early history as follows: In some of the Silurian ostracoderms (Lanarkia) the teeth of later vertebrates are represented by thorny sha- green denticles embedded in the skin all over the surface of the body, but the ostracoderms them- selves did not have teeth in the mouth. In the sharks the skin on the inside of the mouth and jaws carries the teeth, which represent only enlarged dermal denticles. In the sharks the tooth-bearing skin on the inner side of the jaws is rolled inward in a spiral manner and as the old teeth are broken off the new ones unwind or rotate into place. In the lobe-finned or crossopt fishes, representing the ancestors of the amphibians, at least the larger teeth arise from pockets of bone sunk below the surface of the bony enamel-covered skin. In these forms the bases of the teeth are deeply and complexly infolded and the pockets of bony skin 117 OUR FACE FROM FISH TO MAN are infolded into the bases of the teeth. The teeth succeed each other in an oblique series. In Seymouria, a fossil reptile from the Permo- Carboniferous of Texas, which is almost on the borderline between the primitive amphibians and all the higher levels of vertebrates, clear traces of the labyrinthodont method of tooth-attachment are still visible, but by the time of the higher mammal-like reptiles all traces of the older method had been lost and the teeth are set in sockets as in the mammals, including man. ORIGIN OF THE MAMMALIAN PALATE No less important in determining the course of future evolution in the mammals and in man were the progressive changes in the palatal region (Fig. 53). In the early amphibians the air taken into the olfactory chamber was passed through a pair of tubes opening by the choane (Fig. 53 II, cho.) or internal nostrils, into the fore part of the roof of the mouth, and from this point the inspired air was practically swallowed, or forced backward by the action of the throat muscles to the opening of the windpipe. In the early mam- mal-like reptiles (Fig. 53 V) the choanz opened 118 OUR BEST FEATURES into a depression or chamber lying considerably above the general level of the tooth-bearing margins of the upper jaw and they may have been the beginning of a fleshy palate. In the higher mammal-like reptiles or cynodonts (Fig. 52 VI) a secondary palate or bony roof of the mouth was formed by horizontal ledges that grew out from the palatine (pl) and maxillary (mz) bones and formed a shelf below the chamber where the internal nostrils opened. Very possibly the increasing muscular power and mobility of the tongue, which pressed against the inner side of the upper tooth-bearing bones, may have favored the evolution of bony shelves from the palatine and maxillary bones. In the mammals (Fig. 52 VII-X) (including man) this process is carried much further so that in the adults the bony palate is prolonged much farther backward. To the rear end of this bony palate the soft palate was attached. In this way the naso-pharyngeal air passage was formed, by means of which the inspired air is delivered almost directly to the windpipe, instead of having to pass through the food-containing cavity of the mouth. All this is associated in the higher mammal-like reptiles and 119 OUR FACE FROM FISH TO MAN early mammals with the very active respiration of carnivorous animals. The anti-evolutionists may be interested to learn that at a very early stage of its development the human embryo (Fig. 65) passes through a stage in which the olfactory capsules, like those of sharks, have no internal opening on the palate but are AncopsyS( 3 ORGAN X: Ar SS NG MOUTH A Fic. 65. Earty Empryonic STAGES IN THE DEVELOPMENT OF THE Nose in MAn (AFTER KEITH). merely extended backward and downward toward the mouth. Later (Fig. 66) the choane, or internal openings of the olfactory capsules, develop in the fore part of the roof of the mouth, but there is only the beginning of a secondary palate and the conditions in the reptiles (Fig. 66B) are recalled (Keith, Corning). In this connection Keith (1921, pp. 158, 159) summarizes the evolution of the human face as follows: 120 : N nostril i} groove ,-—“\ to ruth Jacobson$ cartilage 2\- Palate -vomer 5 *~LUSTaCaAIA tool or pharyiix tube Fic. 66. ComparaTIVE ANATOMY OF THE HUMAN PALATE. A. Recent shark, showing groove from nose to front of mouth. (After Keith.) B. Lizard, in which internal opening (choana) from the nose opens in the forepart of the mouth cavity. (After Plate.) C. Lion pup with cleft palate, recalling in form the palate of reptiles; showing internal opening of the nose (indicated by the arrow- point) in the forepart of the mouth cavity. In this abnormal specimen the secondary palate has failed to grow over to the midline. (After Keith.) D. Human embryo at the end of the sixth week, showing the secondary palatal plates beginning to grow in toward the midline and the “primitive choane”’ (arrow-point) still exposed in the forepart of the roof of the pharynx. (After Keith.) (B, from Allgem. Zool., Gustav Fischer.) 121 OUR FACE FROM FISH TO MAN In our survey of the neural part of the human cranium we have seen that its outstanding features are the result of a great cerebral development. When, however, we turn to the facial and pharyngeal parts of the skull and head, we find that the factors which have determined their shape are related to the functions of smell, respiration and of mastication. It is unnecessary to again insist on the fact that the human embryo, in the latter part of the first month, shows a resemblance to a generalized type of fish; it possesses the basis of a branchial arch system. As in the fish, the olfactory organ is represented by a pair of pits or depressions, which at first have no communication with the mouth. In some forms of fish—certain rays and sharks—a channel is formed between each olfactory pit and the mouth. The functional meaning of such a channel is evident; the water imbibed is sampled by the nose before entering the mouth. When pulmonary breathing was introduced, as in Dipnoean fishes, the open naso- buccal channel became enclosed by the union of its bound- ing folds. In amphibians, reptiles and birds the naso- buccal channel becomes dilated to form a true respiratory nasal passage, and the parts bounding the passage unite on the roof of the mouth to form the primitive palate. In Fig. 152 the parts entering into the formation of the primitive palate are shown. They are three in number: (1) a premaxillary and vomerine part developed between the nasal passages; (2) a right and left maxillary part, laid down on the lateral or outer aspect of each passage. In mammals a fourth element is added to the primitive or reptilian palate, and in this way the mammalian mouth is separated from the nasal respiratory passage, and can serve the purposes of mastication and suction. Thus in the evolution of the face there have been three distinct stages: (1) a piscine, in which the nose and mouth were formed independently; (2) an amphibian stage, where the nasal respiratory passage opened on the roof of the mouth; (3) a mammalian stage, in which it opened in the naso- 122 OUR BEST FEATURES pharynx. In the development of the human embryo we see these three stages reproduced. EVOLUTION OF THE TONGUE AND RELATED STRUCTURES In Amphiorus (Fig. 54) there is no tongue and in the lampreys and hags the so-called tongue with its enclosed cartilages probably represents the lower jaw of the shark (Stockard, Goodrich). In the shark the folding up of both the jaw cartilages and the gill cartilages causes the lower ends of the latter to project forward in a series of V’s into the floor of the mouth (Fig. 7). These cartilages support the tongue proper, which at first is only a thickening of the floor of the mouth covered with epithelium containing the “taste” cells. In some of the amphibians the tongue becomes highly muscular and protrusile and by the time we reach the lower mammals the tongue is fundamentally the same as that of man. The early primates have a long narrow tongue with a well developed “under tongue”’ beneath it; in the higher primates, especially the orang, chimpanzee and gorilla, the tongue approaches the human type but is longer in proportion to its breadth. In the detailed number and arrangement of the papille 123 A Fie. 67. Lonerrupinat Section or Heap 1n Youna Gortua (A) AND IN Man (B), SHow1ne ReLation or Tonaur To SuRROUND- ING Parts (arrer Kiaatscn). 124 OUR BEST FEATURES vallatze the orang agrees with man (Pocock, Sonntag). Fic. 68. LonorrupinaL Section or Lower JAw or Monkey (A) AND IN Man (B), SHowinc ATTACHMENT OF THE TONGUE MUSCLE To THE Back or THE JAw (AFTER RoBINSON). C. Diagram of the genioglossus muscle in pronouncing the sound oo.” D. Diagram of the genioglossus muscle in pronouncing the letter ““T.”” (C, D, after Robinson.) For details, see pp. xxviii, xxix. The muscles of the tongue are the same in the anthropoids and man (Figs. 67, 68) but in the latter 125 OUR FACE FROM FISH TO MAN the geniohyoglossus muscles have acquired the abil- ity to change the precise shape and position of the different parts of the tongue with extreme rapidity and in conjunction with movements of other parts of the voice-producing mechanism (Robinson). The great size of the tongue in man and its important function as the leading organ of speech has doubtless partly conditioned the later stages in the evolution of the lower jaw, especially in the region of the chin, to the back of which the tongue muscles are attached (Fig. 68). Meanwhile the remaining part of the branchial arches has given rise to the larynx with its highly elaborate voice mechanism, to the tonsils, thyroid and thymus glands, the last two being of vital importance in the normal growth and differentia- tion of the individual. Again the anti-evolutionist can offer no alternative scientific explanation of the fact that during the course of embryonic development the human tongue, larynx and adjacent structures reveal remarkably detailed resemblances to corresponding structures of lower vertebrates.‘ The “‘gill-slits’ in the human « For a clear presentation of the details see Keith, Arthur, 1921, Human Embryology and Morphology, London, pp. 240-252. 126 OUR BEST FEATURES embryo (Fig. 69) have been heard of by multitudes, so that certain anti-evolutionists have tried to Fic. 69. Human Emsryo or THE TurrD WEEK (FROM EIDMANN, AFTER His). Oblique front view of the head, showing mouth, primary upper and lower jaw buds, gill arches and gill slits. (From Entw. d. Zihne . . ., Hermann Meusser, Berlin.) offset their effect by arguing that they are not gill-slits since gills are not present. But this could only confuse people unfamiliar with the evidence that each of the so-called “gill-slits”’ of the human embryo of the fifth week may be compared directly with a corresponding one in 127 OUR ‘FACE FROM FISH TO MAN the foetal and embryonic stages of other mammals, of reptiles, amphibians and primitive fishes, and that in the fishes these clefts are definitely associ- ated with functional internal gills. The anti-evolutionists should also be embar- rassed by the fact that, leaving the embryonic stages aside, and considering only adult anatomy, the entire complex of the hyoid arch, larynx and associated parts in man corresponds in great detail with those of the anthropoids, differing only in the proportional development of certain parts. From the anthropoids down through the lower primates the homology of every segment of the hyoid arch and laryngeal complex can be completely estab- lished and from thence these structures can be traced backward step by step through the reptiles to the lower amphibians and thence to the elaborate branchial skeleton of the crossopt or lobe-finned ganoids. In fact the branchial skele- ton of vertebrates, in all its complex relations with the muscles and nerves and in its successive stages of development, affords convincing evidence of the anatomical unity of the entire vertebrate series from shark to man. The human jaws, tongue, larynx and associated parts thus con- 128 OUR BEST FEATURES stitute only a single manifestation of a morpho- logical theme that has a thousand variations, but is everywhere patently evolved from a shark-like prototype. And in particular this region yields most cogent evidence of man’s unity of origin with the anthropoid apes. The salivary glands under the tongue and in the sides of the cheek and throat afford another example of the same kind. Huntington has shown how even the variations in man are obviously related to those of the higher primates. ORIGIN AND EVOLUTION OF THE HUMAN LIPS Let us return now to the outside of the mouth and consider the origin and evolution of the human lips. The mouth in the lowest existing chordate Amphiorus (Fig. 54) is surrounded by short stiff projections. Much the same condition obtains in the larval lamprey (Fig. 59B). In the adult lamprey the mouth cavity is surrounded by a movable ring of cartilaginous plates beset with thorn-like teeth, probably a very specialized arrangement. In the ostracoderms (Figs. 4, 57) of the Silurian the border of the capacious mouth cavity was covered with small scales and plates. 129 OUR FACE FROM FISH TO MAN In the modern sharks there is a fold of skin at the back of the upper border of the mouth that seems to foreshadow the maxillary or upper jaw bones of higher fishes (Allis). Underneath this fold of skin at the corner of the mouth are two labial cartilages embedded in muscles which apparently serve to draw forward the corner of the mouth (Fig. 6). A similar fold of tooth-bearing skin (Figs. 50, 53) in the lobe-finned ganoids, or crossopts, gives rise to the premaxillary and maxillary bones, which have every appearance of being homologous with the bones that bear the same name in the earliest amphibians, and from thence these two bones can be followed through the mammal-like reptiles to the earliest mammals, thence through the ascending grades of primates to man. In the earlier crossopts these bones were covered with enamel and lay right on the surface but in the more advanced crossopts the ganoine layer has disappeared and the outer surface of the bone is rough, indicating that it was covered with a thick tough skin. The dentary bone of the lower jaw was likewise covered. In the early amphibians and reptiles the pre- maxilla, maxilla and dentary were likewise rough- 130 OUR BEST FEATURES ened for the attachment of the outer layers of the skin, of which they themselves formed the deeper layers. In some of the recent reptiles there is a small muscle at the corners of the mouth but the lips are not fleshy and the tough facial mask is not far below the surface. Probably the same condi- tions obtained in the entire series of mammal-like reptiles. In the most archaic mammal living today, the Duckbill Platypus of Australia, the mouth is surrounded by a duck-like bill consisting of leathery skin well supplied with sense organs. Very possibly this condition is a specialized remnant of the tough skin that covered the mouth of the mammal-like reptiles. In the Spiny Anteater (Echidna) of Australia (Fig. 23C), the nearest living relative of Ornithorhynchus, the lips, although peculiarly specialized in connection with the ant- catching, protrusile tongue, approach the normal mammalian condition in so far as they are supplied with muscles that are innervated by the seventh or facial nerve and are covered with hair rather than scales. Here we arrive at the most distinctive feature of the lips of mammals, in which the bony mask 13] OUR FACE FROM FISH TO MAN inherited from the primitive crossopts lies deeply covered by a mobile fleshy curtain. Doubtless the evolution of true lips was a part of the general transformation of reptiles with unstable body temperature and low grade metabolism, into mammals living at high pressure. In an earlier chapter (pages 43, 44) it has been mentioned that the facial muscles of mammals represent a forward extension of a thin layer of muscle covering the neck of lower vertebrates and that when this muscle migrated forward beneath the skin it dragged its own nerve with it, which was subdivided into smaller branches as the muscle itself was differentiated into the facial muscles of the ears, eyes, nose and lips (Figs. 23, 24). The history of this invasion is now being traced in convincing detail by Huber. The inva- sion was facilitated by the fact that in the early stages of development (Figs. 65A, 69) the region of the mouth and lips arises quite close to the original territory of the facial nerve, which was on the side of the neck, so that forks of the parent mass in the neck could easily spread to the lips and forehead. The researches of Ruge, Huber, Sonntag and 132 Fic. 70. Onp CHIMPANZEE, SHOWING EXTRA- ORDINARY PROTRUSION OF THE LIPS IN ANTHROPOIDS. (From J. A. Allen, from a photograph by Herbert Lang.) OUR BEST FEATURES others have shown that the anthropoids (as usual) are man’s nearest living relatives in the anatomy of the facial muscles. The ability to move the ears is already reduced in the anthropoids but some men can still make a creditable showing of activity in these souvenirs of man’s earlier mam- malian ancestors. In the lower primates the opposite upper lips, like those of carnivorous mammals, depend slightly at the sides and are barely, if at all, joined in front, but in the anthropoid apes and man the median flap of the foetus, forming the philtrum of the lip in adult man, becomes very broad, so that the opposite halves of the orbicularis oris muscle become broadly continuous. Thus the anthropoids acquired: highly protrusile lips, useful in sucking up water and the juices of fruit (Fig. 70). Man has inherited from the primitive anthropoids the ability to draw back his lips in anger, to open them in a laugh, or again, to protrude them into a funnel and soto confer kisses on the objects of his affection. How much dour literature, ancient and modern, might be lightened by this thought! All these muscles of the mouth and cheeks as 133 OUR FACE FROM FISH TO MAN well as the muscles of swallowing were naturally of vital importance to the newborn mammal, enabling it to pump the mother’s milk into its swelling cheeks. But how long it took mankind to realize the deep significance of the fact that even babies of bluest blood share this birthright with the beasts of the field. LATER STAGES IN THE HISTORY OF THE TEETH Thanks to the advertisers of tooth pastes all America knows the practical importance of beauti- ful teeth. But few indeed share the secret as to how we obtained these dazzling objects of charm, and fewer still ever give a thought to the humble creatures who slowly shaped them to our use. It is surprising that even today, after hundreds of millions of years’ advancement beyond our shark- like ancestors, each human being, during the embryonic development of his teeth, starts at a shark-like stage (Fig. 71A). For at first the area of embryonic skin that is destined to give rise to the teeth lies on the surface of the mouth cavity, then it sinks down like a pouch (Fig. 71B), the bottom of the pouch is pushed upward (Fig. 71C) to form a pulp cavity and thus the germ of the 134 OUR BEST FEATURES human tooth becomes essentially like the germ of the shark’s tooth. However, in order to defend Zooth pouch tooth-beariv. A SKIL 7 : Lower aur Meckels Cone cartilage C Ds ee ee ee Fic. 71. Turee Empryonic STaGks IN THE DEVELOPMENT OF HUMAN Trers (A, B, rrom ErpMAn AFTER AHRENS; C, AFTER CORNING). (A, B, from Entw. d. Zihne . . ., Hermann Meusser, Berlin; C, from Lehrb. d. Entw. des Menschen, J. F. Bergmann.) For details, see p. xxix. the validity of these comparisons it is essential to note that we are not leaping at once from shark 135 OUR FACE FROM FISH TO MAN to man in the reckless manner of some of the older comparative anatomists, but that the same general process of tooth development may be traced in many successive grades in the ascent from fish to man. Meanwhile (Fig. 71C) Meckel’s cartilage, the descendant of the primary lower jaw of the shark, lies entirely free from the future dentary or lower jaw bone, which will later surround both the Meckel’s cartilage and the developing tooth-germ, as in all the vertebrates above the shark. In the earlier creatures that lie in or near the line of ascent to man the teeth were of the dog- tooth or canine type (Fig. 50). Some of the front teeth of man, especially the cuspids or canines, remain single-cusped to this day as souvenirs of our remote carnivorous ancestors; but the central incisors often exhibit a tendency to develop little cusps, mammillz or subdivisions, along the flat- tened cutting edge of the crown (Fig. 72). The frequent presence of these mammillz on the edges of the central incisors has sometimes been cited as evidence of a ‘“‘triconodont”’ stage in the evolution of human teeth, in disregard of the fact that not even the extinct triconodont mammals of the 136 OUR BEST FEATURES Fic. 72. Centra Incisors or Goria (A, E) ann Man (B, C, D, F). Enwuarcep. (B, arter WeEINERT, C. F, arterR VircHOW; D, arter HroutKka; G, rrom HrpuicKa, AFTER ZUCKERKANDL.) For details, see pp. xxix, xxx. Triassic age themselves had “‘triconodont”’ incisors but only triconodont molars. In whatever way this tendency to subdivide the central incisor 137 OUR FACE FROM FISH TO MAN edges may have arisen, man shares it with many other mammals, especially with his relatives the anthropoid apes, whose central incisor crowns approach the human type. Remane (1921, Fig. 21E) has shown that in certain chimpanzees even the outer rim of the central upper incisor is vertical as in man. Hrdlicka has noted that on the rear surface of the central upper incisors of certain anthropoids « and monkeys one finds the “rim and ridge” formation (Fig. 72) of many human incisors. In the upper central incisors of recent Mon- golians and many Indians the rims along the sides of the crown fold around toward the rear and the ‘“‘shovel-shaped”’ incisor is developed. This arrangement was already foreshadowed in certain gorillas and is almost fully attained among the extinct Neanderthals of the Krapina race; it has also recently been discovered in a fossil human tooth from the Pleistocene of China. In its extreme form the shovel-shaped incisor represents a distinct specialization beyond that attained in the anthropoids. Dr. J. Leon Williams has observed among all races of mankind the presence of three types of central upper incisors (Fig. 73). 138 OUR BEST FEATURES In the first type the inner and outer borders of the crown as seen from in front tend to be straight and vertical; in the second type the opposite borders diverge sharply toward the lower end of the crown; and in the third the outer border has a Se) Y | AOI Poy) Fic. 73. Toe Tourer Types or CEenTrAL Upper INcisors (AFTER J. Leon WILuIAMs). Lower row, first type; middle row, second type; upper row, third type. marked double curve. Exactly these same three variants he found also in all the existing species of anthropoid apes and he rightly considers that this fact, taken in conjunction with hundreds of other items of similar purport, affords decisive evidence of close kinship between man and anthropoids. The upper lateral incisors in anthropoids (Fig. 74) as a rule are more primitive in retaining the 139 Fic. 74. Pauatan ArcHES OF ANTHROPOIDS AND Men: A G1BBON, FEMALE; B. GorILLA, Mae; C. Cuimpanzer, FE- MALE; D. Oranea, Femare; E. NEANDERTHAL Man; F. Mop- ERN Waite Man, Composite. (A, B, C, F, from Selenka, after Rose; D, after Hrdlitka; E, from Weinert, after Dieck.) OUR BEST FEATURES bluntly pointed tips, but Remane (1921, page 102) figures a certain chimpanzee in which the tip of the lateral upper incisor is submerged in a transverse incisal edge and even the outer rim is vertically developed, so that the crown as a whole is clearly approaching the human type. The great outstanding difference between the dentition of man and that of his anthropoid cousins lies in the fact that in man the canine teeth, even in the milk set (Fig. 76) are much reduced in size, with rounded crowns and obtuse tips that project but little above the level of the adjacent teeth, while in the anthropoids, especially the males, the canines form large sharp-tipped tusks. If, however, the fossil lower jaw found at Piltdown, England (Fig. 45C), belongs with the human Piltdown skull, as nearly all authorities now believe, it affords a clear case of an ape-like canine belonging in a human jaw; only it should be noted that the Piltdown canine is much more like the lower canines of certain female gorillas, which have not attained the tusk-like stature of male canines. The human canines may indeed be most reasonably regarded as reduced and *‘infantilized”’ or ‘‘feminized”’ derivatives of a 141 OUR FACE FROM FISH TO MAN primitive anthropoid type and the process of reduction and infantilization may well have taken place during the millions of years of the Lower Pliocene epoch, at a period when the fossil record of human remains so far discovered is still blank. The great mass of collateral evidence for the derivation of man from primitive anthropoids with well developed but not greatly enlarged canines, has been reviewed lately with great thoroughness by Remane, who finds no justification for the view that man has avoided the primitive anthro- poid stage and has been derived from wholly unknown forms with the canine tips not projecting much beyond the level of the premolars. When the skull of a chimpanzee (Fig. 35F) and the skull of a high type of man (Fig. 43D) are viewed from above, the ape is seen to differ widely from man in the marked projection of his muzzle. This projection is less in female anthropoids with smaller teeth and still less in early foetal anthropoid stages before the tooth-germs are formed. On the other hand, savage types of man with very large teeth have a correspondingly prominent muzzle, especially if the molar and premolar teeth have large fore-and-aft diameters, as in the fossil 142 OUR BEST FEATURES Talgai, Australia, skull (Fig. 42E), which has a strongly protruding muzzle. Again, the Piltdown lower jaw (Fig. 45C) with its “simian shelf’’ in front, its female anthropoid canine and its ape- like molar teeth (Fig. 41A), must indubitably have had a muzzle approaching that of an immature female gorilla. By the time we reach the Heidel- berg and Neanderthal fossil men, however, the canines had become reduced to the level of the cheek teeth, the incisors and premolars were reduced in size and the lower molars were relatively wider than in the anthropoids; hence Professor McGregor’s very thoroughly studied restorations show these men with only moderately developed muzzles and human lips. The reduction of all the front teeth in man is foreshadowed in the foetal stages in which the tooth-germs are smaller than those of apes; consequently the foetal muzzle is likewise smaller than that of foetal apes of corresponding stages. The reduction in size of all the teeth, especially the canines, has been an important factor in shortening the palatal arch (Fig. 74) from the long ()-shaped type of anthropoids, with a wide space between the canines, to the short human 143 OUR FACE FROM FISH TO MAN form of palate with narrow space between the canines. In the lower jaw the diminution of the lower canines and the backward retreat of the incisors finally brings the canines almost to the Fia. 75. Lowrer Front Premouars or Fosstnr ANTHROPOIDS (A, B, C) anp Man (D, E). (A, B, after Gregory and Hellman; C, after Pilgrim; D, after Virchow; E, from Selenka, after Rése.) For details, see p. xxx. front of the jaw and into functional alignment with the incisors. The upper premolars or bicuspids of man, which in the adult dentition are two in number on each side of both the upper and lower jaws, find their nearest relatives in the bicuspid upper and lower premolars of the anthropoid apes (Fig. 74). The front lower premolars of the anthropoids show a wide range of forms, from types with a more compressed baboon-like crown to the almost human premolars of the extinct Swapithecus (Fig. 75C) 144 OUR BEST FEATURES and of certain modern chimpanzees. Remane records the fact that in certain human jaws the front lower premolar retains clear vestiges of the asymmetrical form of the outer surface of the crown, a condition that is far more accentuated in the typical anthropoids and is there associated with the large size and tusk-like form of the upper canines. Neither the upper nor the lower molars of man show much resemblance to those of the cynodonts or pro-mammals of the far-off Triassic age (Fig. 771); yet we owe to such lowly forbears the initial phases of the process by which the simple dog- tooth crowns of the cheek teeth began to subdivide and give rise to the accessory tips or cusps that are so characteristic of the cheek teeth of mammals. Anti-evolutionists ask us to believe that even the hairs of our head are numbered, but we affirm only that our teeth are numbered: twenty in the milk set and thirty-two in the permanent sets of normal individuals; and that the same numbers oc- cur in the anthropoid apes; that typical represent- atives alike of mankind and of the apes, have in the permanent dentition two incisors, one canine, two premolars, three molars, on either side in both 145 lower \ Canine A OUR FACE FROM FISH TO MAN the upper and lower jaws; and in the milk set, two incisors, one canine and two milk molars on either side above and below (Fig. 76). The history of the human upper and lower premolar and molar teeth (Figs. 77, 78) has been Two nailk c7CesOrs lower. canine twomilk molars B cower Fic. 76. Mitx Terra or Man (A) anp GortLua (B). (BoTH FROM SELENKA, AFTER RO6sE.) discussed at length by myself in the work on the Origin and Evolution of the Human Dentition and other papers and by Gregory and Hellman in our work on The Dentition of Dryopithecus and the Origin of Man. We have shown that not- withstanding the present profound differences in habits between man and the anthropoid apes, the lower molar teeth, especially of more primitive and more ancient races of man, retain the most 146 ‘Ixxx ‘d 908 ‘s[Ivjap 10,7 *(WaumIdads [eUIsII0 WIOIJ) [eJUSORTd DAIWIMINIG “A *(uetMIOAdS [vUIZIIO WIOIJ) 9Ye[NOIOqQNyI4I}-O1g “AJ ‘(WosduIIG ‘Iq Jo ssou ~pury) [eyueovjd-oid aanimiug “[{J *(Aejaeg saqye Ayureu) optydei oy!-femMeM poourApy ‘TT ‘(A2]e0g 49772) a[YdeI VyT-[eMUTeM psourapy of ‘(WMooIg 49}Je) o[IVder Oyl[-[eUMUMEM sATIUNNIG “ql “(WOT J0}Je) V[tYde1 Ydiomo19y} sAT}IUIIg “RT ‘SNOZINOPF TVOIDOIO’Y ONIGNGOSY WOUd NOILILNAG NVWOP{s AHL dO NOILOIOAG FHL NI SANVLG IVAOLONULS NAT, “LL ‘SIs “L ff ty tf Vepepexece °° od eh 2 Al Do git ee ue wad lf \ > Ps ef gt) &) & . 9 > y \ hy » ; i y: alternation of the “‘rods’’ and “‘cones”’ of more ¢ advanced types of eyes, in which the “rods” are believed to detect light and darkness, form and 175 OUR FACE FROM FISH TO MAN movements, while the “‘cones”’ chiefly detect color differences (Plate, 1924, p. 705). In the jelly- fishes the cavity of the optic pouch is often filled with a transparent jelly-like substance correspond- ing to the “glass body” or vitreous humor of higher eyes, and functionally to the lens. That these organs are really eyes, says Plate (1924, p. 428), follows from the fact that if the animal is deprived of them it fails to react in its normal way to light. In some of the flatworms the eyes consist of hollow capsules derived from an infolding of the epithelium and deeply lined with pigment. Each capsule has sunk beneath the epithelium, which has grown over it. It is open on one side and into its hollow interior project the flower-like ends of the “‘light cells,” the outer ends of which pass into elongate nerve cells. Hesse (quoted by Plate, p. 433) notes that if two such capsules are symmetrically arranged on either side of the mid- line, then a light in front will give symmetrically placed shadows inside the capsules, a light on the left side will illuminate the left capsule and leave the interior of the right one in shadow, and so forth. Thus the nerves inside the capsules on 176 OUR BEST FEATURES opposite sides of the body will be stimulated differently according to the direction of the light Y ct ea Fic. 92. Eyre Capsutes or Fiuatworm: (B) Section or “GoBLEetT Eye” (rrom Puiate arrer Hesse); (A) Location or EyYEs (AFTER PARKER AND HASWELL). (B, from Allgem. Zool., Gustav Fischer.) For details, see p. xxxv. and according to their own orientation in the body. Here the function of paired eyes in enabl- ing the organism to adjust its own axis of locomo- tion to the direction of the light comes into view. RT OUR FACE FROM FISH TO MAN Indeed, Plate (1924, pp. 738-742) cites much evidence for his view that the paired eyes of vertebrates originated as directional organs, guiding the animal toward the light and that later by acquiring a lens they became true visual organs. a =a a6 oe Y Fic. 93. How tHE Eyr Capsu.es or A FLATWORM SERVE AS DIREC- TIONAL ORGANS (FROM PLATE, AFTER Hesse). The arrows show the varying directions of the light. In each case only a particular part of each retina is stimulated, the rest being in shadow. (From Allgem. Zool., Gustav Fischer.) The higher invertebrates exhibit eyes in all grades of evolution, from the simple types described above to the compound eyes of crustaceans and insects and to the elaborately constructed paired eyes of the higher molluscs. Eyes occur in various parts of the body and sometimes in great numbers, as in certain deep-sea cephalopods. The common scallop (Pecten) has numerous eyes along the scalloped edge of the mantle. Thus in typical invertebrates the eyes are essentially derivatives of the skin and may occur almost anywhere on the 178 OUR BEST FEATURES surface of the body, but in the vertebrates the paired eyes are essentially an outgrowth of a definite part of the forebrain, only the outer parts of the eye (including the lens and cornea) being contributed by the epithelium; although eventually x S A ~ Y ny Lf} = = 8 MUTT yi , ® Bo As g Qs Ti . NS YMA A *s St) arts 78 ee ~Ss “iy \ Gy) RY SS Eye or Seuip (Horizontat Meprian Section). (From PLATE, AFTER HENSEN.) (From Allgem. Zool., Gustav Fischer.) Fic. 94. the brain itself has been derived from the same primary outer layer or ectoderm. Among all the hosts of invertebrates the paired eyes which at first seem to approach the vertebrate type most nearly are found in some of the ceph- alopod molluscs, especially the squids and 179 OUR FACE FROM FISH TO MAN octopuses. In these highly elaborate organs there are eyelids in front of the eyes, a contractile iris, muscles of accommodation, a highly complex retina of many layers, a large optic nerve and muscles to move the eyeball. But when we compare the parts of these cephalopod eyes with those of vertebrates we find many striking and profound differences. Thus in the squid (Sepia) the lids serve as a pupil, there are two corneas, the outer one perforated, the inner one dividing the lens into inner and outer parts; the so-called iris lies entirely outside of the retinal layer instead of next to it as in the vertebrates; and there is apparently no true choroid layer. More important still, in the cephalopods the optic nerve lies entirely behind the retina, while in vertebrates it pierces the retina and is then distributed over its front surface; finally, in the cephalopods the rods are on the front layer of the retina, pointing toward the light, while in the vertebrates they are on the back layer of the retina and point in the opposite direction. Not all the cephalopods have eyes as compli- cated as the type described above and there is a gradation of forms leading back to the very 180 OUR BEST FEATURES simple eye of Nautilus (Plate, 1924, pp. 474-478). The retina and indeed the whole eye of cephalopods develops in the embryo as a pouch in the skin, and is thus comparable only to the lens of vertebrates; in the latter the retina is developed from the optic Fic. 95. DrvELOPMENT OF THE Err IN CrPHALOPOoD Mo.uuscs. (ArTER PuaTe.) (From Allgem. Zool., Gustav Fischer.) For details, see p. xxxvi. cup, which is an outgrowth of the brain. Thus at every important anatomical point the paired eyes of cephalopods and of vetebrates differ profoundly from each other. From all this it is evident that the paired eyes of cephalopods and of vertebrates are not homologous with each other at all, that they have arisen from dissimilar beginnings and have come to resemble each other 181 OUR FACE FROM FISH TO MAN by convergent evolution in adaptation to similar functional needs. The paired eyes of the modern Limulus and the scorpions represent specialized offshoots of the annelid and primitive crustacean types (Plate, 1924, pp. 537-561). Patten and others have attempted to show how they might have been tranformed into the vertebrate eyes, but most authorities consider that there is no direct evidence in favor of this view and the profound differences between the eyes of arthropods and those of vertebrates have always been considered a grave objection to Patten’s theory of the origin of the vertebrates from arthropods related to the euryp- terids and to Limulus. ORIGIN OF THE PAIRED EYES OF VERTEBRATES We have seen above that a comparative study of the eyes of invertebrates shows several steps in the evolution of such elaborately constructed paired eyes as those of the cephalopods and there- fore gives us a general idea how the somewhat similar paired eyes of vertebrates may have been produced. More direct evidence as to the origin of the vertebrate eye is wanting. The lancelet 182 OUR BEST FEATURES Amphioxus, which, as all beginners in zoology learn, supplies us with an ideally simplified chordate, goes too far for our present purpose in the simplifi- cation of its eyes, which have either vanished entirely by degeneration or never developed. A B ze. Fic. 96. Ligur Crentus or Ampnioxus: (A) Forepart or A YOUNG Amphioxus, ENLARGED; (B) CROSS-SECTION OF THE SPINAL CoRD OF AMPHIOXUS (FROM PuiatTsE, A, AFTER JosEPH, B, arreR Hesse.) (From Allgem. Zool., Gustav Fischer.) For details, see p. xxxvi. According to Plate (1924, p. 494) the lancelet (Amphioxus) when resting on the sandy bottom is supposed to sense the direction of the light by means of long rows of minute eye-like organs, which are deeply buried in the spinal cord and extend along each side of the back above the notochord. Each little eye consists of a single cell, supposed to be sensitive to light, backed by another cell which is concave and deeply pig- mented. A much larger spot of pigment at the 183 OUR FACE FROM FISH TO MAN front end of the brain tube is interpreted by Plate (1924, p. 493) not as an eye at all, as it lacks light cells, but as the last remnant of a balancing organ. Thus the light-sensing apparatus of Amphioxus is of the utmost simplicity and has little obvious relation to the highly complex paired eyes of vertebrates. In the foregoing pages we have reviewed the general construction of paired eyes, we have out- lined the evolution of eyes from very simple beginnings, we have considered the wide contrast between vertebrates and invertebrates in the structure of the paired eyes and we have seen that according to present evidence the vertebrate paired eyes do not appear to be inherited from any of the more complex invertebrate types but seem to have arisen in the very ancient and still undiscovered pre-vertebrates. As direct evidence from successive fossil stages illustrating the origin of the paired eyes of vertebrates is meager or wanting and as there are apparently no surviving pre-vertebrate stages except possibly Amphiozus, we must rely chiefly upon the evidence afforded by embryology, and such evidence is often open to the suspicion that we may be mistakenly inter- 184 OUR BEST FEATURES Parapineal pupeal Ss S N WN INLD NS S > YY G YZ, GCLGLL yy y YSU LLY Wb Vfliip, Vay Gi, Gy OU Lyd OY oh “flit “4 b;7 0%, me orn YA, CED, 21177; LY, LZ LLL, Ue, Ci. Liglfe. Nn SS WS ANN Sd \ » ’ Fic. 97. Evoiution oF THE VERTEBRATE Eyr As CONCEIVED BY Srupnicka (FROM PLATE, AFTER STUDNICKA). (From Allgem. Zool., Gustav Fischer.) For details, see pp. Xxxvi, XXxVil. 185 OUR FACE FROM FISH TO MAN preting as a repetition of long past adult stages such arrangements or conditions as may be merely adaptations of the growing embryo to its own physiological needs. Studnicka (quoted by Plate), basing his theory chiefly on the embryology of the lampreys and their relatives (which may represent the degenerate descendants of the ostracoderms), holds that originally there were two pairs of paired eyes in the pre-chordates, one pair dorsal, on the top of the head, consisting of the pineal and parapineal organs, the second pair low down on the sides of the head, the eyes of later vertebrates. Both pairs were derived from patches of cells sensitive to light, located in the broad sensitive tract that later folded up to become the brain tube. Up to this time both sets of eyes had served merely to orientate the animal with reference to the direction of light. When as a result of its growing mass the primitive nerve tract swelled outward, its crests grew upward and curved over toward the mid- line, carrying the primary optic depressions on to ‘ its inner side, so that the future “‘rods” would now point away from the light, and their nerve fibers, formerly beneath them, would now be bent 186 OUR BEST FEATURES around toward the outer surface. Meanwhile the dorsal pair near the front edge of the brain tract were not turned over, so that their retina remained on the outer side of their nerve layer. As the brain swelling increased it pressed the future optic cups against the epithelium on the surface of the head; the epithelium sank inward, folded up into a lens, and the lens in turn increasing rapidly, conditioned the insinking of the optic swelling, which thus became the optic cup. The optic stalk or nerve is simply the constricted part between the brain and the cup. By this time the lateral paired eyes were becoming true organs of vision, while the dorsal pair gradually degenerated and their nerve stalks finally became the pineal and parapineal organs of the brain. It is important to remember that the retina apparently represents an inverted patch of epithelium and that the layer of nerve fibrils now covering it represents the former underside of the patch. Also that the optic cup was pushed in from the outside so that its primary cavity was squeezed out of existence. The lens is at first connected with its parent epi- thelium by a slender stalk, whichis soon lost. The lens thus finds itself protruding into the hollowside of 187 OUR FACE FROM FISH TO MAN the pushed-in ball, or optic cup. The space between the lens and the inside of the cup becomes filled with fibrillar tissue which gives rise to the transparent jelly-like substance called the vitreous humor. The retina, derived from the inner layer of the cup, comprises the following series of layers: the innermost of these is a layer of nerve fibers and ganglion cells which are gathered together and pierce the center of the cup, issuing from it as the optic nerve; next follow various layers of large and smaller nerve cells, culminating in the layer of cones and rods, the latter being nearest the outer epithelial layer of the inner wall and directed away from the source of light. The outer layer of the optic cup gives rise to the pigmented layer of the retina, which doubtless provides the neces- sary opaque, light-proof layer, like the black inner surface of a camera. Next comes the network of blood vessels of the choroid, while outside of the choroid is the thick sclerotic layer, which is continuous in front with the cornea. ORIGIN OF THE HUMAN EYES Before attempting to trace the evolution of the human eye, let us recall its broader structural 188 OUR BEST FEATURES features. We know that it is essentially like a camera, with its dark chamber (the inside of the eyeball), its lens, its sensitive plate (retina), its iris-diaphragm for regulating the amount of light admitted through the pupil. We know also that it differs from an ordinary camera in altering the focus not by regulating the distance between the lens and the plate but by changing the curvature of the elastic lens through the pull of the ciliary muscles. We also know that the human eye differs from a single camera in being linked with its fellow of the opposite side so as to provide for a binocular, stereoscopic mental image and that the two eyes are biconjugate, that is, by means of its six eye muscles (Fig. 98), each eye can move in harmony with its fellow so as to keep a moving object in focus; also that the eye is a living mechanism provided with elaborate systems for the elimination of waste, for automatic renewal of all parts and for the lubrication, cleaning and protection of its exposed surface. The retina carries a coloring matter named rhodopsin or visual purple, which becomes rapidly bleached on exposure to sunlight. No doubt the * Cunningham, D. J., 1902, Textbook of Anatomy, p. 689. 189 OUR FACE FROM FISH TO MAN extent and intensity of the bleaching effect is in some way proportional to the size of the aperture, the intensity of the light and the length of exposure. And no doubt also the innumerable rods and o0bliguus superior ‘i rectus / wnjperior obdi9 WDA Bear © 7 Wy, \\\ Fic. 98. Tuer Rigut Eyesaut AND Its Six Musciss (From PuatTs, AFTER MERKEL AND KALLINS). (From Allgem. Zool., Gustav Fischer.) cones of the visual field react differently to different wave lengths (colors) and different intensities (light and shade), so that an image made up of innumerable points, like a half-tone picture, is recorded on the retina. But whereas the photog- rapher proceeds after an interval to fix the image 190 OUR BEST FEATURES on the plate, the retina immediately proceeds to be “televisualize”’ its images through the myriads of nerve fibers covering its surface. After passing through many microscopic relay and “booster” stations the disturbances pass along a vast cable route known as the optic nerve. Instantly reaching their first main destination, the visual cortex of the brain, the visual currents now incite millions of repercussions which are flashed and reflashed to the relay stations and great central systems in many parts of the brain, where they set off many triggers that control the secretory activities of glands or the contractility of muscle fibers. The foregoing description holds in a general way for the eye of vertebrates of all grades from fish to man, the vertebrate eye, except in degenerate forms, being extraordinarily constant in its main features. Hence the basic features of the human eye date back to the beginnings of the vertebrates and are fully exemplified in such primitive forms as the sharks (Fig. 99). The six eye muscles of the human eye (Fig. 98) likewise date back at least to the shark-like stage. Here again the shark is vastly nearer to man in the essential features of its 191 OUR FACE FROM FISH TO MAN morphology than it is to any known invertebrate. In other words, while we can only surmise what the history of the eye may have been below the verte- brate stage, we have the most convincing evidence that once that grade of organization of the eye had ctliary muscles COTHCA ie es il Of shell Fic. 99. Tue Ricut Eyre or A SHARK IN HorizontaL SECTION (FROM PLATE, AFTER FRANZ). (From Allgem. Zool., Gustav Fischer.) been attained, it was transmitted by heredity with only minor improvements from fish to man. Although the human eye is undoubtedly derived remotely from one that was in general like the shark type (Fig. 99), from which it has inherited even the principal layers of the retina, it shows also many progressive changes beyond that of the shark in adaptation to vision in the air rather than in water. Its lens, being relatively smaller and 192 OUR BEST FEATURES flatter than that of the shark, gives a longer focus, and accordingly the focal axis of the bulb is lengthened, the human bulb being spherical while that of the shark is flatter in front. The cornea in optic merre = {J ot ae Fic. 100. Dracram or HorizontAL SECTION OF THE Ricgut Human Eye (SIMPLIFIED FROM PLATE, AFTER LUCIANI). (From Allgem. Zool., Gustav Fischer.) man is more convex and widely separated from the lens, which is entirely behind the iris, whereas in many sharks it protrudes through the pupil and touches the cornea. The human lens is much more delicate, less dense, more easily compressible than that of the shark and it readily responds to the pull of the ciliary muscles of accommodation. 193 OUR FACE FROM FISH TO MAN As to the external accessories of vision, man retains a vestige of the nictitating membrane or third eyelid of lower vertebrates in his semilunar fold at the inner corner of the eyelid; but he has advanced far beyond the shark in possessing an elaborate lacrymal or lubricating apparatus, con- pica semilunaris ' earuncula / ‘acrymal / sack Fic. 101. TEaAR-pRAINING CANALS OF THE Eye (AFTER KEITH). sisting of tear-producing glands, with two collect- ing canals above and below the caruncula. These two canals converge toward and drain into the lacrymal sac, which is lodged in a pocket of the lacrymal bone on the inner wall of the orbit; the lacrymal sac is continued downward through the naso-lacrymal duct into the nasal chamber. Man also has fleshy, movable eyelids, which are pro- vided with eyelashes and Meibomian glands. Many similar details could be cited in which the human eye is superior to that of the shark; but 194 OUR BEST FEATURES the anti-evolutionist could find little justification for setting man apart from the rest of creation on this account, for we find that every one of the characters cited above is the common property of normal land-living mammals and that the evolution of some of these structures, such as the lacrymal apparatus and the third eyelid, can be traced with convincing detail through the various branches of the vertebrate tree lying between the human and the shark branches. Moreover we are compelled to cause even further distress to the indomitable critics of the Darwinian theory of human origin by bringing forward again their special horror, the anthropoid apes and monkeys. For nowhere will more convincing mor- phological evidence of the relatively very close re- lationship of man to these animals be found than in a detailed comparison of the anatomy and physiology of the paired eyes. And when to these resemblances in the visual organs between man and anthropoid, we add the striking identity in the complex arrangements and connections of the optic tracts within the brain, as reported by the lead- ing students of the human and anthropoid brains, the evidence for Darwin is heaped still higher. 195 OUR FACE FROM FISH TO MAN The position of the eyes in the human head has likewise been inherited from the common man- anthropoid stock. In Notharctus, a _ primitive primate of the Eocene epoch (Fig. 35A) the eyes were directed partly outward as well as forward, the large muzzle extended far in front of the orbits and binocular vision was obviously impossible. The large size of the olfactory chamber in Notharctus also indicates that like other mammals and especially like its relatives the modern lemurs, the lowest existing primates, it still depended largely upon its olfactory sense, while the higher primates have a much reduced olfactory apparatus and a predominant visual apparatus. With regard to the direction of the orbital axes, these look partly outward also in most of the modern lemuroids (Fig. 35B) and even the greatly enlarged orbits of the modern Tarsius (Fig. 35C) are directed somewhat away from each other. In the South American monkeys (Fig. 35D) however, the outer angles of the orbits are shifted further forward and the muzzle is reduced; in the Old World monkeys and anthropoid apes (Fig. 35E, F), this process is completed and binocular vision is established. The binocular character of the vision of anthropoids and 196 Fic. 102. Front View or Inrant anp_ YouNnG SKULLS OF Anturoporps (A, B, C) anp or Man (D). For details, see p. xxxvii. 197 OUR FACE FROM FISH TO MAN man is especially evident in the front views of the young skulls (Fig. 102). Meanwhile we observe a general progression in the character of the hands, which in the lemuroids are hardly more than forefeet, while in the gibbon, chimpanzee and gorilla the anterior extremities are true hands, adapted primarily for brachiation or leaping with the arms, a habit which requires the greatest quickness in adjusting the focus of the eyes and in correlating the locomotor activities with the rapidly changing visual data. To the brachiating habit of his ancestors man doubtless owes much of his skill in discriminating the relative nearness of different objects. Brachia- tion would also seem to be greatly facilitated by biconjugate movements of the eyes. Broman and John I. Hunter have shown that in the chimpanzee the nucleus in the brain of the oculomotor nerves, which controls several of the eye muscles, has essentially the same pattern as in man and differs widely from that of the lower primates which have not attained biconjugate movement of the eyes. The surface of the iris as seen through an ophthalmoscope differs widely in different kinds of animals. Lindsay-Johnson in his beautiful 198 OUR BEST FEATURES monograph on the fundus oculi of vertebrates figures the retinal surface of the eye of many mammals, including a white man, a negro and a chimpanzee. The deeply pigmented iris of the chimpanzee shows the most striking resemblance to that of the negro, while its basic similarity to that of the white man is masked by the loss of pigment in the latter. Only man and the apes have a macroscopic “‘macula lutea” or spot of clearest vision on the retina (Plate, 1924, p. 690). The lacrymal bone, in the inner corner of the eye, affords additional evidence of the close relationship of man and the anthropoids. Not only are its general form and connections strikingly similar in man and chimpanzee (save for the very small size of the “hamular process”’ in the apes) but Le Double notes: that in Deniker’s gorilla foetus the lacrymal bone begins to ossify in the same place that it does in the human fcetus to- ward the end of the fourth month, namely, in the covering membrane of the ethmoidal cartilage and on the inner side of the lacrymal sac; that, like the human foetal lacrymal, it consists of an « « Essai sur la Morphogénie et les Variations du Lacrymal et des Osselets péri-lacrymaux de Homme.” Bibliographie Anatomique, 1900, T. VIII, p. 125. 199 OUR FACE FROM FISH TO MAN oval plaque with its long diameter inclined obliquely from above downwards and from within outward. Le Double further notes: that during intrauterine life the human lacrymal is successively oval, triangular and quadrilateral in form, that the lacrymal of the gorilla is almost triangular, while those of the adult chimpanzee and orang, which show so much resemblance to the human lacrymal, are also subject to the same variations in form. CONCLUSIONS In conclusion, the human eyes owe their begin- nings to the sensitivity of protoplasm both to the injurious and the beneficial effects of light. In their early pre-vertebrate stages they seem to have been merely directional organs to orientate the animal’s locomotion with reference to the light, serving the same purpose at the lower sides of the head as the pineal and parapineal eyes did on the top of the head (Fig. 97A). At this stage the eyes were still on the inner side of the brain tube. When the brain grew outward into contact with the epithelium the optic cup acquired a lens Ibid., pp. 128, 129. 200 OUR BEST FEATURES and true vision resulted, greatly enhancing the organism’s success in the pursuit of living prey and in the escape from its enemies. Then various accessory organs appeared, for regulating the focus of the lens, either by slightly changing its position with reference to the opening, or by altering its curvature. After the air-breathing fishes crawled out of the swamps their eyes had to become accustomed to functioning in the air and we find further improvements in the accessory devices for accommodation and for protecting and keeping in repair the whole delicate apparatus. These devices culminate in the mammals, in which however for the most part the olfactory ap- paratus rather than the eyes is still the dominant sense organ. The primates, alone, show a _ pro- gressive reduction of the olfactory sense and a concomitantly increasing importance of the eyes, which is further emphasized in the arboreal brachiating anthropoids. In man, a secondarily terrestrial offshoot of the primitive anthropoid stock, the eyes retain not only all the advantages won by the vertebrates in their earlier predatory career, but also all the improvements resulting from a prolonged course of very active life in the 201 OUR FACE FROM FISH TO MAN trees. Starting with all this experience the eyes of the first true man not only cooperated with the hands, but filled the brain with memory pictures, and these, on the principle of conditioned reflexes, came to be associated in definite com- binations with the memories of vocally produced sounds. Thus man’s eyes and ears, rather than his nose, provided him with the means of rising above the endless round of life known to his predecessors, of turning his observational powers upon himself, and eventually of foreseeing not only the immediate but also some of the distant effects of his own activities. PRIMITIVE SOUND RECORDERS The human organ of hearing (Fig. 103) consists of three main parts: (1) the external ear, for collect- ing the sound waves; (2) the middle ear, including the tympanic or drum-membrane and the tym- panum or middle-ear chamber, the latter con- taining the three auditory ossicles, the office of which is to transmit the vibrations of the drum membrane to the inner ear; (3) the inner ear, or labyrinth, comprising (a) the three semicircular canals with their basal connecting chamber or utriculus, the canals and utriculus being concerned 202 semicircular canals labyrinth eo ner ear) INCUS oi tnalleus £2 aa ween, cochlea (Jy miaddleearcarily stapes drum membrane = ey ( DOPE) asCCn ATH. U Spiralduce A branches of hearing nerve C Fic. 103. Tar Human Organ or HEARING AND BALANCE. (A) Transverse section (after Cunningham); (B) Diagram section of the cochlea; (C) Greatly enlarged view of the cochlear duct. For details, see pp. XXXVii, XXXViii. 203 OUR FACE FROM FISH TO MAN with the sense of balance; (b) the cochlea, a spirally-wound double tube filled with liquid and containing between the upper and lower inner tubes the spirally-wound organ of Corti, the true organ of hearing. The sound waves in the air cause the drum membrane to vibrate, the ossicles magnify the movement and set up mechanical waves in the liquid of the cochlea. It is these mechanical waves and not the sound waves them- selves that are picked up by the little rods of the organ of Corti and transmitted to the nerves of hearing. In the more primitive fishes at the lower end of the vertebrate series there is no middle ear and the inner ear consists chiefly of the semicircular canals, which may be followed throughout the series without a break from fish to man. The labyrinth arises in the embryo shark, as in the embryo man, by the formation of a sac or pocket in the ectoderm or outer cell layer on either side of the tube that gives rise to the hind brain. The sac later becomes surrounded by cartilage which finally ossifies. The nerves of the semi- circular canals appear to be part of the fore and aft series that innervates the “‘ampulle”’ of the 204 endolymphatic auct wertor barat T branches of Gags or erve branches QCOUSTIC a Her ie lagena } (beg¢nni: sei) an S27 ENS TOK rier, \ g up. \\Why ampulla Fic. 104. Serres SHowrne THE MemBranous LAByRINTH OR INNER Ear rrom Fish to Man. Ricut Sipn; OuTER View. (Arter ReErzivs.) A. Shark; B. Ganoid fish; C. Primitive reptile; D. Alligator; E. Rabbit; F. Man. For details, see p. xxxviii. 205 OUR FACE FROM FISH TO MAN shark (Fig. 6) and the lateral line organs in the skin of most fishes. These organs are sensitive to the disturbances caused in the water either by wind or by objects falling on the surface of the water (G. H. Parker). Below the semicircular canals there is a sac-like depression (Fig. 104A) ently mph. auct Fic. 105. DevevopMentT or Tae Lapyrinta or Inner Ear oF Man (arrer Srreeren). frequently containing an otolith or calcareous secretion which may function in the sense of bal- ance. The nerve that goes to the semicircular canals also sends off a branch which is attached to the otolith, and this lower branch, in the higher vertebrates, is the nerve of hearing (Fig. 104D-F). It is doubtful whether fishes can really hear rather than feel sound waves in the water. The true organ of hearing equivalent to the cochlea of man has its inception apparently in the Amphibia 206 OUR BEST FEATURES in the shape of two small papille which grow out from the side of the sac below the semicircular canals. In the crocodiles and alligators one of these papilla is prolonged into a curved tube (Fig. 104D) and in the mammals (Fig. 104K, F) the tube is wound into a spiral, the cochlea. Thus while the semicircular canals which are concerned with balance show only minor changes as we pass through the long series from shark to man, the organ of hearing in air has its beginnings in the Amphibia and culminates in the typical mammals, from which it is transmitted intact to the apes and man. The chamber of the middle ear (Fig. 106) in the frog (which represents a comparatively little- modified survivor of the earliest amphibians) is derived in the embryo from an out-pocketing from the throat, corresponding to the first or hyoid gill pouch of fishes. This chamber is therefore lined with the entoderm, or primary inner cell layer. The Eustachian tube of the frog is the short passage connecting the cavity of the middle ear with the cavity of the throat. By this arrange- ment the outward pressure of the air inside the mouth and throat neutralizes the inward pressure 207 OUR FACE FROM FISH TO MAN of the air outside the ear-drum. Likewise in all higher vertebrates, including man, the cavity of the middle ear communicates with the throat through the Eustachian tube; this arises in the SMI TULAL CQNQLS 4 * pga “ynpanit Cibrarne oblongata. Sam << Kg XO J aoustiC LYNDANIC NVC ® Tae Lustachian Zube Fic. 106. TRANSVERSE SECTION OF THE HEAD IN A FROG, SHOWING THE RELATIONS oF THE MrippLEe Ear (THERE Is NO OuTER Ear) TO THE INNER EAR AND OF THE LATTER TO THE BRAIN (AFTER T. J. Parker anp W. N. Parker). embryo as an outgrowth of the primitive throat cavity immediately behind the first or jaw arch (Frazer, quoted by Keith). The tube of the outer ear of mammals corre- sponds in position partly to the spiracle or hyoid gill cleft of the shark. Both arise also in the embryo as a down-pocketing of the ectoderm, which meets an out-pocketing from the throat 208 OUR BEST FEATURES cavity called the hyoid gill pouch. In the stur- geon, a survivor of the primitive ganoids, W. K. Parker’s plates of a very young embryo show the hyoid gill cleft lying in front of the upper part of the hyomandibula, or upper segment of the second gill arch. A spiracular cleft was also present in ra are Dd gilicletés Olfactory pit Fie. 107. Empryro SturGron, SHowING GILL CLEFTS (arteR W. K. Parker). the oldest fossil lobe-finned ganoid Osteolepis (Watson). In the earliest known amphibians and reptiles the spiracular cleft may be represented in part by the otic notch (Figs. 17, 19) upon which the tympanic membrane was stretched. In the fishes the gill chamber behind and below the spiracle was covered externally by the bony opercular flap, but in the oldest known amphibians this bony gill cover has disappeared, leaving the prominent otic notch open behind. 209 OUR FACE FROM FISH TO MAN In the frog, a modern representative of the Amphibia, there is no external ear tube, since the tympanic membrane lies on the surface (Fig. 106). In the reptiles a ridge or fold of skin may guard the drum membrane and in the birds and typical mammals the latter has sunk so far below the sur- face that a deep tube is formed. That the mammalian outer ear tube corresponds only at most in part with the spiracular pocket of the shark is indicated by the fact that the outer ear tube of mammals is formed below the Eustach- ian tube (which represents the lower part of the first internal gill pouch), while in fishes the spir- acular pocket is formed from the upper part of the spiracular cleft and lies above the first internal gill pouch. In Echidna, one of the egg-laying mammals, G. Ruge found that the cartilage of the external ear was continuous with the hyoid, or second gill arch, and hence the inference was drawn that the external ear cartilage was derived from the hyoid arch. But Gaupp’s figures of the embryo Echidna show the hyoid cartilage entirely distinct from the external ear. And the relations of the ear tube to the tympanic ring both in Echidna and in other 210 OUR BEST FEATURES mammals indicate that its cartilage is a new local development in the mammals. The outer ear in mammals takes on a great diversity of forms, from the trumpet-like ear of antelopes and other keen-eared, defenceless herbi- vores to the huge and imposing ear-flaps of the Fic. 108. Human (A) ann Macaque (B) Emsryos, SHow1ne ORIGIN OF THE ExTERNAL Ear From Srx Tuspercues. (From LEcuE, A, AFTER SELENKA, B, arter. His, KerseEt.) (From Der Mensch, Gustav Fischer.) African elephant. Some of the bats have large ears of extreme complexity, while the whales have only a thread-like tube beneath the skin that marks the last vestige of the external ears. Very little in detail is known either about the precise functioning of the different forms of external ear or about the origin and significance of its many subdivisions, such as the tragus, antitragus, crus of the helix and antihelix and the marginal fold or 211 OUR FACE FROM FISH TO MAN descending helix and lobule. According to Keith (1921) in the human embryo of the sixth week all but the marginal fold arise from six tubercles that form around the first gill cleft depression. Three of these tubercles [writes Keith] grow from the mandibular or first arch and form the tragus, crus of the helix, and helix; three from the hyoid arch to form the lobule, antitragus and antihelix. The hinder margin of the ear, or descending helix, with the lobule, arise as a mere thickening or elevation of the skin behind the tubercles in the hyoid arch. Later in development the tubercles of the helix and antihelix send out processes which cross the upper part of the cleft and obliterate it, while the neigh- boring tubercles fuse to form the definite parts of the ear. The posterior margin and lobule rise up at the same time as a free fold. Fic. 109. Ears or Fa@rat Macaque (A) AND or A Srx Montus Human Farvus (B). (From Puats, AFTER SCHWALBE.) (From Allgem. Zool., Gustav Fischer.) The common lemur (Lemur catia) of Madagascar has very large pointed ears that can be directed forward. In the monkeys the ear tends to be flat with a rounded top, quite different from the trumpet-like ear and not capable of being thrust far forward. The ear of the Old 212 Fig. 110. Externat Ears or ANTHROPOIDS AND MEN. (Arter KetTH.) A. Chimpanzee; B. “Small chimpanzee type” (human); C. “Chim- panzee type” (human); D. Orang; E. “Orang type” (human); F. Gorilla; G. Gibbon; H. Lemuroid (Nycticebus). 213 OUR FACE FROM FISH TO MAN World or catarrhine monkeys shows various stages in the reduction of the pointed tip (cf. Pocock, 1925, Fig. 36). The ear of a six-months’ human foetus (Fig. 109B) figured by Schwalbe has a truncate upper rim and vestigial tip and in general appearance approaches the Old World monkey type (Fig. 109A) as noted by Schwalbe. The un- rolled outer rim and Darwin’s point, found as an occasional variant in man, is reminiscent rather of the monkeys than of the anthropoids, although indications of the Darwin’s point are not lacking in certain chimpanzees (cf. Heckel, 1903, Pl. 26) and in certain orangs (Pocock, 1925, Fig. 37D, E). The ears of the great anthropoid apes, while highly variable in details, are substantially of the human type, especially those of the gorilla. All have the rolled-over upper rim, but in the chim- panzee the hinder rim, according to Pocock (1925) is ‘“‘sometimes flat, sometimes slightly overfolded but never apparently so overfolded as is typically the case in Homo. The lower lobe, varying in size, is not so well developed as in Man.” On the whole the external ears of the gorilla and chim- panzee are remarkably human in appearance and, like so many other features of anthropoid anatomy, 214 OUR BEST FEATURES they are literally one of the earmarks of man’s relatively close relationship to the primitive brachi- ating ancestors of the chimpanzee-gorilla stock. If man had been derived from some entirely differ- ent stock of Primates there is no assignable reason why he should resemble the gorilla and the chim- panzee in so many external and internal characters in spite of his widely different habits and notwith- standing the millions of years that have passed since the human and gorilla-chimpanzee groups began to separate. Since the time of Darwin the reduced ear muscles of man have been justly famous as indi- cations of our derivation from mammals with more movable ears. Ruge’s monograph (1887, Plates V, VI, VII) on the facial musculature shows very clearly the striking resemblance between the ear muscles of the chimpanzee and those of certain human embryos and children (cf. also Fig. 23D, E). ~~ The evolution of the auditory ossicles (Fig. 111) has been referred to earlier in this book but may be summarized here as follows. The most ancient member of the ossicular chain is the stapes, or stirrup, which has probably been derived from one of the two upper segments of the second or 215 OUR FACE FROM FISH TO MAN hyoid gill arch of fishes. In the oldest known amphibians, as in the frog (Fig. 106) the stapes “Wis tonaton af ie TCGUQUHG arum ) Membrane Ze oo." D4 Hh y (PAM Oe Sts ee eeusenvil) —_headofmaileus attic. oa (hammer) VIE oe “at Chorda iympuni @igD OSSIMG (70g a é 20\\ Filagle O3\ 5 Car Chamber COgtool, pie 2 fe Fooiplaieof 23 - SCOMCS (Situ) °2222 2 ef ig Ge tye odd Wis into rymerear | OC fgets Lustachiar i sachian (*eyolating muscle) Fig. 111. Tare Mippite Ear or Man, SHowine THE AUDITORY OssicLes (AFTER CUNNINGHAM). For details, see p. xxxix. extends from the inner ear to the tympanum or drum membrane. When the tympanum first ap- peared (in the Amphibia) it was fastened (Fig. 216 OUR BEST FEATURES 17B) to the back part of the squamosal bone, or bony shell over the back part of the primary upper Fic. 112. Revations or THE Parts or THE MIDDLE EAR IN AN Extinct MaMMAL-LIKE REPTILE (AFTER SUSHKIN). For details, see pp. xxxix, xl. jaw. In the reptiles the tympanum is always associated with this same region and is also more or less connected with the angular bone of the Q17 OUR FACE FROM FISH TO MAN lower jaw. In the fossil mammal-like reptiles a large notch (Figs. 112, 113) in the back of the US IMCUS ‘ =Qd. oa ae Soar \ = Sw a OE Ns SSS N\ - ae a MEKELS NY ah Pa ANB nee CARTILAGE (pEuEfistete) “7VMP Fic. 113. Oriein or Aupitory OssIcLEs. (A) Back part of the lower jaw of an advanced mammal-like reptile (based chiefly on a cast of the specimen combined with observations and figures of Seeley and Watson); (B) Foetal mammal (slightly modified from R. W. Palmer). For details, see p. xl. angular bone is thought for various reasons to have served for the attachment of a pocket from the membranous sac that encloses the cavity of 218 OUR BEST FEATURES the middle ear. The stapes was connected with the inner ear on the inner side and by its double outer end (Fig. 112) with both the quadrate bone and the tympanic membrane. When the dentary bone became very large and formed the chief part of the lower jaw, the angular, articular and quad- rate elements, which were still connected with the tympanum, became much smaller. When the dentary formed its new joint with the squamosal (pages 36-39) the lower jaw bones that were behind it (quadrate, articular and angular) gave up their function as jaw elements and intensified their auditory function, transforming sound waves into mechanical pulsations and thus transmitting the equivalents of the sound waves to the stapes; this in turn passed them on to the liquid in the inner ear. In this way arose the marvellous delicate mech- anism of the auditory ossicles, the tiny muscles of which (Fig. 111) are still innervated, even in man, by twigs from the main nerve of the jaw muscles. Meanwhile the first gill pouch, below the back part of the jaw, had grown upward and surrounded the now reduced angular, articular and stapes, forming the cavity of the middle ear (Fig. 112). 219 OUR FACE FROM FISH TO MAN The human embryo, like that of mammals of all other orders, still shows in the clearest, most unde- niable way, the origin of the malleus and incus from the reduced primary jaw elements (Figs. 114, 115). ANCIENT AND MoprEerRN PHYSIOGNOMY The art of reading character from the human face is one of the things that every woman knows and every man prides himself upon. But the courts are crowded with the wrongs of deceived women and the prisons are filled with wolves in sheep’s clothing who have hidden a ravenous heart behind faces that confident physiognomists, in- cluding practical men of business, have diagnosed as honest. What is the matter then with the popular “‘science”’ of physiognomy? To the ancients, never embarrassed by facts, physiognomy was as easy as every other branch of science. Aristotle, according to the Encyclopedia Britannica (article on Physiognomy), taught that noses with thick bulbous ends belong to persons who are swinish; sharp-tipped noses belong to the irascible, those easily provoked, like dogs; large rounded, obtuse noses to the magnanimous, the lion-like; slender hooked noses to the eagle-like, 220 INTERARTICULAR DISK (MEWISCUS ) CKELS. Abit ibe Fic. 114. Rewations or Ossictes to Lower JAW IN Farat ARMADILLO (Tatusia hybrida). (Composed from two figures by W. K. Parker.) GOWIALE (PR EARTICULAR) MECKELS CARTILAGE J bite (ANGULAR 3 HILLEUS : . : “-UNMCUS - : een 7 SMANUBRIVH B Fig. 115. Tue Reprinian STAGE IN THE DEVELOPMENT OF THE AUDITORY OSSICLES. A. Lower jaw and attached auditory ossicles in a foetal hedgehog (after W. K. Parker). B. Lower jaw and attached auditory ossicles in a human fcetus (after Macklin). For details, se 221 GICA/ goos YOST LIBRARY |= et OUR FACE FROM FISH TO MAN the noble but grasping; round-tipped retroussé noses to the luxurious, like barnyard fowl. This is the kind of rubbish that passed under the name of science for more than two thousand years. Other self-appointed and equally successful teachers classified men and faces as mercurial, saturnine, jovial and so forth, according to the positions of the stars that ruled their fates from birth, so that physiognomy, like palmistry, was clearly linked with astrology. The modern science of physiognomy, if it be a science, began when artists and sculptors tried to record the facial expressions of emotions and of moral character and when actors tried to repro- duce these expressions on the stage. Much valu- able descriptive material was thus accumulated and expressions intended to represent piety, devo- tion, suffering, anger, malice, joy and the like, may be seen in any collection of old masters or any antique treatise on physiognomy. A great step in advance was taken in 1806 when Sir Charles Bell in his Essay on the Anatomy of Expression inferred the action of the mimetic or facial muscles in producing the characteristic expressions of the emotions. 222 Fic. 116. Young CnimpanzEr SHowrne FactaLt Expression. (From a photograph by Herbert Lang.) OUR BEST FEATURES The experimental method of studying physiog- nomy was founded by Duchenne (Mechanisme de la physiognomie humaine, Paris, 1862), who showed that by the use of electricity the action of the separate muscles could be studied and by the aid of photography accurately represented (Encycl. Brit., XI Ed., Art. Physiognomy). In Darwin’s book on the Expression of the Emotions (1872) it was shown that man and the apes agreed in expressing equivalent emotions by means of homologous facial muscles (Figs. 23, 24, 116). Thus the subject of physiognomy was brought under the evolutionary point of view. At the present time the general subject of physiognomy or the systematic investigation of the human face is being pursued according to the following methods. First, the evolutionary meth- od, as in the present work, endeavors to answer the question, by what stages did the human face arrive at its present form? From the evolutionary viewpoint each type of face among the lower animals is associated with a definite pattern of behavior. Hardly a beginning has been made in tracing the evolution of behavior or in correlating the details of facial character with neuro-anatomy. 223 OUR FACE FROM FISH TO MAN Second, the anthropological method studies the variations of the face in different races and en- deavors to arrive at general concepts of pure and hybrid racial types. Third, the ontogenetic or embryological method describes the development and growth of the head as a whole and of its several parts. Fourth, the genetic method studies the heredity of facial characteristics, tracing through successive generations the results of homozygous and heterozygous matings with reference to par- ticular features. Fifth, the physiological method studies the chemical factors of the growth and development of the face, including those growth- stimulating substances that the embryo derives from its parents and those that are produced by its own various endocrine glands. Sixth, the clin- ical method notes that certain types of face are frequently associated with low resistance to cer- tain diseases and seeks to determine the causes of this association. Seventh, the psychologic or behavioristic method endeavors to determine whether there are measurable correlations between definite combinations of features and grades of intelligence. Can an expert predict from exam- ining faces alone which individuals will score high 224 OUR BEST FEATURES and which low? Eighth, the student of crime and criminals endeavors to discover correlations be- tween certain types of face and constitutional pre- disposition to crime. Ninth, the psychoanalyst will undoubtedly seek for traces in every face of the sore conflict between the “‘censor”’ and the rebellious subconsciousness. Tenth, the psychia- trist, studying pathologic types of mentality, may approach his material from any of the above described paths. Let us see now how much room there is for the old-fashioned physiognomy. I undoubtedly inherit the general ground-plan of my face from my excessively remote shark-like ancestors who possessed paired olfactory capsules, paired eyes and paired internal ears, arranged in the order named, and who had a medium mouth below the nose and eyes. I also owe to these humble creatures the framework of my tongue and vocal organs, my jaw and throat muscles and many other features both useful and necessary. Next, I owe to the primitive lobe-finned fishes or crossopts the complete bony scaffolding of the face and jaws, which in them lay on the surface but in my own face is deeply buried beneath the flesh. Then I owe to the higher mammal-like reptiles 225 OUR FACE FROM FISH TO MAN the fact that the right and left halves of my lower jaw are composed of a single piece and that I have a set of teeth limited to the margins of the jaws and differentiated into incisors, canines, pre- molars and molars. I also owe to these hitherto much neglected animals the “‘basic patents” for the delicate apparatus of my middle ear, together with my bony palate and several other important parts of my make-up. In the earliest mammals the bony mask became covered with mobile, sensitive flesh; to them I owe also the very hairs of my head, my eyebrows, eyelashes and other facial accessories. To my earliest primate ancestors I owe the large size of my eyes and a considerable part of my brains. To my friendly anthropoid ancestors I am heavily indebted: for eyes that can focus on things near at hand, that give stereoscopic pictures and that follow closely the flight of a moving object; for a nose that is a real nose and not a snout; for lips that can smile and laugh or curl up in anger or kiss in love; from them I inherited all my baby teeth and my thirty-two adult teeth; the very shape of my ears is theirs. 226 OUR BEST FEATURES To my early human ancestors I owe the reduction of my hitherto coarse muzzle and the first training of my tongue to speak. To my later human ancestors I owe the improve- ment of my forehead, the general refinement of my features and my rather weak jaw. To the Nordic strain in my ancestry I ascribe my fair skin and blue eyes, while to both the Nordic and the Mediterranean strains I owe my narrow head and a nose of moderate dimensions, conforming neither to the figure-6 type nor to the alpine V, nor to any of the concave varieties, but fairly straight and presentable. However, when I have determined all this and much more of the same kind I am still far from giving a description of my face that would satisfy the requirements of Scotland Yard, for most of the features mentioned have been true of millions of men of all ages. There remains then not only the exact measurements and proportions but also the individual history of my face. Fortunately my development proceeded without undue mental stress or sudden prenatal shock. Hence I escaped being a Mongolian idiot. My ancestors do not seem to have had deficient thy- Q27 OUR FACE FROM FISH TO MAN roids and there must have been a fair sufficiency of iodine in my food, for I missed being a cretin. After birth I never developed any notable defi- ciency in either the hypophysis, the thyroids, the thymus or other glands, so on all these counts I missed obesity, and on account of the fair state of the pituitary I escaped gigantism and acromegaly; as the adrenals functioned properly, excessive pig- ment was not deposited in the skin and so I escaped Addison’s disease by a wide margin. Thus owing to all the favorable circumstances of my prenatal development I did not “come into the world scarce half made up”’ but all the various parts of my face joined together in the right order, with no undue accelerations or delays, and so I escaped many distressing inconveniences such as a hare lip or a cleft palate. At the right time before birth I lost the “Mongolian fold” in the inner corner of my eye; nor was my face marked with a nevus. But after birth I had to run the gamut of children’s diseases and no doubt they checked growth to some extent, leaving me with a temporarily impaired heart and a little below the average in stature and weight. On the deficit side also there was a defective turbinate bone 228 OUR BEST FEATURES and a slightly warped septal cartilage of the nose, together with slight malocclusion of certain teeth and a failure of two wisdom teeth to erupt. Thus I may explain my face although I cannot improve it. A specialist in this subject could afflict the reader with many pages of this sort of thing; but the chief object here is to raise this point. Suppose I asked my grocer to open a credit account on short acquaintance; upon which, if any, of the features listed above would he decide to trust me? Would he not trust equally well many other customers with entirely different types of face? And do we not see similar artistic talent, musical talent and traits of leadership, moral courage, etc., embodied in widely different types of face? In short, does not scientific physiognomy and even intuitive physiognomy discount all these and many other such before coming to the small residue of features that may conceivably be corre- lated with particular mental and temperamental qualities? And in order to detect the abnormal must one not know at sight the normal range of variations in all the features in all the races for both sexes from infancy to old age? The studies of Keith, Stockard and others on 229 OUR FACE FROM FISH TO MAN abnormal human types and of Stockard on the parallelism between abnormal human and animal types are all leading to a new understanding of the causes of racial and individual types of faces. The bulldog and a certain type of human dwarf with a broad face and retroussé nose equally owe their peculiar features to a derangement of the normal functioning of the hypophysis, one of the growth-regulating glands. This condition is called achondroplasia and is largely hereditary. In both the bulldog and the achondroplastic dwarf the base of the skull ceases to grow and becomes ossi- fied at an early stage. The rest of the growing head, being confined at the base, grows out at the side and the head thus becomes short in proportion to its width, or brachycephalic. Similarly the median cartilaginous septum of the nose is not pushed forward by the base of the skull, the bridge of the nose therefore fails to rise up and the nose remains flat or actually sunken, giving a marked depression below the forehead. The maxilla, or upper jaw bone, like the base of the skull, fails to grow forward and this causes the lower jaw to protrude beyond the upper, giving a characteristic *undershot jaw.” 230 OUR BEST FEATURES The opposite condition to achondroplasia is known as acromegaly and is due to an opposite disturbance of the normal functioning of the hypophysis-pituitary complex. It is characterized by excessive growth of bone in the linear direction. Human acromegalics are apt to become excessively tall, their faces growing exceedingly long and their chins very protruding. Acromegaly is often but not always associated with gigantism, which pre- sumably results from an abnormally active thy- roid gland. Among the dogs, writes Stockard, the St. Bernard, the mastiff and some others show symptoms of acromegaly along with gigantism. The bloodhound, on the other hand, is a splendid example of the acromegalic type without gigantism and his facial expression and general appearance are closely similar to the human acromegalic. The opposite condition to gigantism, known as ateleosis, is responsible for the production of true midgets, which typically grow normally for five or six years after birth and then stop growing. They may or may not become sexually mature and often retain infantile faces. Among dogs the King Charles spaniel is in “shape, outline and expression almost a picture of the human midget” (Stockard). 231 OUR FACE FROM FISH TO MAN Quite recently Stockard has classified all human faces under two general types, into which almost all ordinary persons fall, the “‘linear’’ and the Fic. 117. Stockarp’s LINEAR AND LATERAL GROWTH Typrs (AFTER STOCKARD). A. Infant; B. ‘‘ Linear” adult; C. “‘Lateral’’ adult. “lateral” (Fig. 117). His linear type is that in which, owing to a high rate of metabolism induced by a highly active thyroid gland, growth along the long axis of the body (from the tip of the nose down the back) greatly predominates over growth 232 OUR BEST FEATURES in the transverse plane. The linear type is the faster-growing, thin but not necessarily tall group. His lateral type, owing to the slower metabolism of low thyroid activity, is slower in maturing and is stocky and rounder in form; that is, the transverse growth components are relatively greater than in the linear type. Stockard’s recognition of these two types was a result of his long experimental work on the factors of growth during the embryonic development of animals. His descriptions of the types are of such fundamental importance for an understanding of racial and individual differences in faces that it is necessary to quote them quite fully: Taking the tip of the nose as the extreme anterior point of the body and viewing the figure laterally, as seen in figure 1 [118] we may draw a line which would indicate the morphological lateral line. This line on each side of the body separates the truly dorsal from the truly ventral surface regions. When these lines on the two lateral sur- faces of the head and body are thought of in space we may imagine that the nearer they come together the more linear is the individual, and the wider apart they diverge the less linear and more lateral the individual type will be. Figure 2 [117] illustrates this in the growth and develop- ment of the two types from the infant condition. Examining figure 2B [117B] it is seen that when the lateral lines are near together the head is of course narrow or dolichocephalic. The interpupillary distance is short and the eyes are close together, the nose bridge is narrow 233 OUR FACE FROM FISH TO MAN and therefore generally high, the mouth arch is narrow and for the same reason generally high, the lower jaw is small and narrow and usually not strongly developed. Fig. 118. Sipe View or Human Ficure, to INDICATE THE ANTERIOR Tir AND THE GENERAL DIRECTION OF THE LATERAL LinE (AFTER STOCKARD). The teeth are usually crowded and somewhat ill-set. The neck is long and small in circumference, the shoulders are square, high and angular, the extremities are long and slender with long slender muscles and slender bones, the trunk is short and narrow, tapering to the waist. The intercostal angle is quite acute. The stomach in such a person is long and narrow and rather vertical in position, 234 OUR BEST FEATURES extending to low in the abdomen and the liver is generally small. The shape of the eye in this type is such that it is usually physiologically far-sighted though not pathologically so. They need no glasses on the street unless for astigmatism or some pathological condition. They are under weight for height according to the crude average tables now in use, and are often so as children. They arrive at puberty rather early than late and differentiate rapidly so that the males develop a large strong larynx and a low-pitched bass or baritone voice. Their skin is thin and sensitive as is also the epithelial lining of their alimentary tracts. When in normal health they rarely laugh aloud and when suddenly shocked they resist the reflex jump and never scream. In this way they pass for cool, calm individuals with steady nerve, but as a matter of fact the body is almost constantly held under nerve control and they are actually nervous, usually suffering more after a shock than on the occasion. The lateral type when fully expressed is the antithesis of the linear type in all of the respects mentioned. The lateral lines are far apart and the head grows wide and not long (Brachycephalic), the interpupillary distance is wide and the eyes are far apart, the nose bridge is wide and often, though not necessarily, low. The mouth arch is wide and low, the teeth are not crowded and are usually smoothly set. The lower jaw is large and strongly developed. The neck is short and large in circumference. The shoulders are round and sloping. The extremities are not long and are stocky with large bones and thick short muscles. The trunk is inclined to be long and full, not constricted but bulging at the waist. The intercostal angle is quite obtuse. The stomach in such a person is large and tends to be transverse and high in position, the liver is generally large. The eye in the lateral type is so shaped as to be anatomi- cally near-sighted instead of far and such persons frequently wear glasses on the street. This type is well rounded and over weight for height and also shows great fluctuations in 235 OUR FACE FROM FISH TO MAN weight, often gaining or losing as much as 15 or 20 pounds in a short space of time. Those of the linear type on the contrary do not experience rapid weight changes but main- tain a very constant weight, and may during the twenty years from about nineteen to thirty-nine vary a small number of pounds. The lateral type arrives at puberty a little late and is slow differentiating, the larynx of the male does not develop so suddenly as in the linear type and does not usually grow so large. The voice is thus high or tenor instead of bass. When men are under thirty years old the heaviest bass voices are almost always found among the thin linear individuals and these are very rarely tenors. The finest tenor voices are those of the round lat- eral type. Everyone recalls that the fine tenor is a fat man while the heaviest bass is a tall thin man. The two types are more clearly expressed in men than in women since the growth and glandular reactions are more decided in the male than in the female and are also freer from physiological disturbances. Many more phy- sical points of difference and contrast could be cited for the groups but the above list is sufficient to make the differences clear. The balance between these two opposite growth tendencies is very delicate and during individual development environmental stimuli may deflect the results now in one direction and later in the other, the exact median between the extremes being seldom realized. As to the inheritance of individual features, Von Luschan, Hooton and other anthropologists have shown that in respect to adult head length and head breadth, nose length and nose breadth and 236 OUR BEST FEATURES many similar measurements, the individual tends to resemble either one parent or the other and not an average between the two. The results of crossing the linear and the lateral types with their opposites are described by Stock- ard (1921-22, p. 62) as follows: Again there are persons who do not properly fall into either type, nor are they typical intermediates, or blends of the two types. These individuals may possess well marked fully expressed features of the linear type along with typically developed lateral features. They may be dolichocephalic with near-sighted eyes, wide palate arches, and tenor voices. Combinations that are at once out of harmony. Such individuals are almost invariably found to be derived from parents of opposite types, and they are very common among the offspring of race mixtures. Environmental influences may tend either to emphasize or neutralize hereditary tendencies. According to Stockard, Keith and others, a person may inherit from his parents a highly active thy- roid gland which under favorable conditions would cause a high rate of metabolism and produce features of the linear type. But owing to disease or deficiency in iodine this person’s thyroid may be checked in its activity and he may to that extent acquire lateral features. On the other hand, another person may tend to inherit a more sluggish 237 OUR FACE FROM FISH TO MAN thyroid gland, which would give him lateral features, but owing to some environmental stim- ulus, such as treatment with thyroxin, his thyroid gland may be stimulated to greater activity and to that extent his features may approach the linear type. Another complication arises from the circum- stance that the growing parts themselves show different degrees of response or receptivity to the hormones or growth-stimulating substances se- creted by the ductless glands. In the dachshund, for example, the bent legs resemble those of the achondroplastic bulldog, while the long muzzle is like those of ordinary large hounds (Stockard, 1923, pp. 269, 273). Whatever influence produced the achondroplastic limbs would have produced a bulldog-like head, if the growing head itself had been receptive to it. One goal of scientific physiognomy would be the ability to control and regulate the environmental factors of growth to such an extent that hereditary defects in the facial make-up could be overcome; while a eugenic ideal would be to encourage the increase of strains tending to produce beautiful faces linked with high intelligence and moral worth. 238 OUR BEST FEATURES In conclusion, the labors of Keith, Stockard, Davenport, Bolk and of the endocrinologists are slowly bringing modern physiognomy toward the goal of ancient physiognomy, in so far as they tend to the discovery of correlations between particular facial characteristics and psychologic reactions. Thus Stockard, for example, writes as follows, giving his impressions of various physical and mental traits associated with the linear and the lateral growth types: The basic psychology of an individual is provably asso- ciated with his structural type. Two persons of the same race and region that chance to be of opposite types show contrasted mental reactions. The lateral type is careful and painstaking, observing details and valuing them and making little effort to get at the meaning of things or draw conclusions until a mass of detail has been accumulated. This type is emotional and expressive, laughs aloud and shows impulses and feeling towards things, the eyes easily fill with tears and the point of view is rarely concealed. The linear type on the other hand has great difficulty in accumulating detail or in working a subject out thoroughly. These individuals have mild respect for details and tend to draw conclusions and see the meaning of things after only a hurried survey. They are not emotional and do not laugh aloud since their reactions are generally under control and their reflexes are suppressed. They conceal their impulses and would be ashamed to shed a tear. This type is self-conscious and nervous, while the lateral type is not self-conscious and not really nervous in the common sense of the word. The linear type has great self-control and among savage tribes the chief is almost always of this 239 OUR FACE FROM FISH TO MAN type, but among civilized peoples the lateral type with near sight and emotion are often rulers of great ability. The lateral type rulers are popular and aware of the details of the immediate situation but are not apt to perceive the great principles of the future. So the linear type Presidents of the United States are honored long after their terms of service, but are often not popular during office, on the other hand, lateral type Presidents perchance of equal ability and equal greatness have been the idols of their time but leave nothing to be remembered in the future. Tue Face or THe Future In the United States the Indians as a whole have not readily adopted the ways of the white man and with few exceptions have not been absorbed into the general population. Hence by outside political and economic pressure they have been forced into relatively small reservations where a great increase in their numbers seems improbable. Except in very limited regions Indians have seldom been able to compete for a livelihood with a more or less antagonistic white population. It is hardly likely therefore that a thousand years from now the Indian features will be very common in the population of the United States as a whole. The negro population, on the other hand, is much larger. But the negro is peculiarly liable to certain fatal diseases and particularly in rural 240 OUR BEST FEATURES districts infant mortality has hitherto been high. In the cities where mixed bloods occur in large number the constant accession of darker features from the country may more than offset the rela- tively slow infiltration of white blood. Moreover the white population is so enormously greater than the negro and has such great economic and social advantages and there is such a widespread and deep antipathy to the marriage of full-blooded > whites and “‘negroes”’ of any shade that it seems highly improbable that the white population will soon absorb the black population en masse. Hence it seems unlikely that the average white man’s face a thousand years from now will show much trace of negroid admixture in the United States as a whole. In many parts of Africa, on the con- trary, the whites are so far out-numbered and the climatic conditions are so unfavorable that it seems probable that a thousand years from now the negro, with perhaps some infiltration of white blood, will still be in the vast majority. Thus we see at once that the average face of the future in any given locality will naturally depend first of all upon the relative increase of one or another racial type in the general population. 241 OUR FACE FROM FISH TO MAN As to the changes in the face of the white race, Sir Arthur Keith has adduced evidence tending to show that a thousand years ago the average English- man had a wider face, a shorter nose, a broader palatal arch and better teeth than the typical Englishman of today, who tends toward a narrow face and a narrow-vaulted dental arch. Keith ascribes this in part to the coarser diet and outdoor life of a thousand years ago, which gave the ductless glands that control growth more chance to produce better teeth and better dental arches. Nevertheless there is reason to believe that in spite of the many unfavorable influences today, espe- cially in the cities, living conditions are on the whole more sanitary, as shown by the decreasing mortality. But while there are better conditions for producing healthy children, more of the weak- lings are also kept alive to perpetuate their troubles. In any event, it is not unlikely that in the long run eugenic counsels will prevail in the more enlightened countries of the world, at least to a noticeable extent. Possibly the people of those days may extract all their teeth before they begin to give trouble, or they may be fed with endocrine and other 242 OUR BEST FEATURES extracts to combat the ills that we now suffer. In any case it seems not improbable that at least for a long time conscious effort will be directed toward correcting unbalanced departures from the types of face that for thousands of years past have been considered good-looking. From all this it appears probable that a thousand years from now the average adult white person’s face will not be profoundly different from what it is today. But what of the human face a million years from now?—a short period compared with its entire history. If present tendencies continue unchecked the white people of those days will for the most part have lost all four of their wisdom teeth so that their total number of teeth will be twenty- eight. This will tend to make their jaws some- what slender. If they no longer eat meat and vegetables but take prepared extracts as food, their jaw muscles and jaws may be further weak- ened. Their brain capacity on the average may be considerably larger. Even under the operation of restrictive eugenic principles there may be at least as great a diversity in normal white faces then as there is today. While some of those people 243 OUR FACE FROM FISH TO MAN might look strange to us, others would remind us at least of certain types we had seen in our own times. In short, the only conservative prediction to make is that the people a million years from now may be far less unlike ourselves than we had at first imagined. But as the determination of the dominant type of human face in the remote future will depend partly upon unpredictable economic and political movements and upon the success in spreading and enforcing eugenic principles, proph- ecy of any kind is obviously rash. If, as many geologists suspect, we are now living in an interglacial period and the continental ice- sheet again covers the northern parts of Europe and North America, then a large part of the white population may be driven to the southern United States and Mexico, with consequent tendency to absorb the more or less colored strains of those regions; but on the other hand, many of the white race may persist along the southern borders of the glaciers. Such speculation is only excusable in order to make the point that prediction of the distant future is far less reliable than deciphering the remote past. 244 OUR BEST FEATURES Looktinac BACKWARD The mobile mask in front of men’s brains began to attract our attention when we were babies and continues to fascinate us as long as we live. Its signals have vital meanings to us: we vari- ously respect, admire, love, hate or are bored by it. But we cannot escape it. It dominates litera- ture and with its mystical symbolism it broods over religion. Let Science interrogate the sphinx, let her expose the intricate and delicate mechanism by which the mask is operated, let her even show that the human face, with all its charms, is but the end of a long series of useful improvements upon simple beginnings. Yet the transformation of the face from fish to man will lose none of its wonder. 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Yerkes, Ropert M. 1925. ‘‘Almost Human.” New York, 8vo. 260 INDEX Acanthias, labyrinth of, Fig. 104, 205 Achondroplastic dwarf, nose of, 169, 171; development of skull in, 230 Acorn-worm (Balanoglossus), theory of relation to ancestors of vertebrates, 93; larva of (Tornaria), Fig. 55, 93 Acromegaly, causes and effects of, 171, 231 Adapidae, feet compared with those of lemur, 54 Adapis, skull of, Fig. 53, 85 African pygmy, nose of, 164, Fig. 89, facing 170 Alar cartilages, of mammalian nose, 167; growth power of, 170 Alligator, labyrinth of, Fig. 104, 205; ear of the, 207 Alligator-gar, resemblance to De- vonian ganoids, 23 Allis, Edward Phelps, Jr., head of shark figured by, 13 Amblystoma punctatum, of, Fig. 14, 26 Armenian, nose of, Fig. 89, 170 Amphibia, in coal-beds of Great Britain, 27; restoration of Eogyrinus, Fig. 15, 28; Wat- son’s studies of early, 28; disappearance of bony plates over gill-chamber, 29, Fig. 17, 30, 89, 114; middle ear of earliest, 29; lower jaw of, 29; teeth of, 31; teeth similar to those of lobe-finned ganoids, 31; enlargement of para- sphenoid, 31; breeding habits of, 32; development of, 32; period of dominance of, Fig. 25, 46; man’s debt to, 89; primary upper jaw becomes attached to skull, 104, Fig. 62, embryo 105; covering of primary jaws in early, 106; skull compared with that of crossopt, 107, Fig. 63, 108; close relatives of osteolepid crossopts, 114; elimination of internal gills in adult stage, 114; feeding habits of, 114; unspecialized, nearest to line of ascent to man, 115; respiration of, 118, 158; naso-buccal channel of, 122; tongue of, 123; first true ear in, 207; section of head of, Fig. 106, 208; otic notch of, 209; stapes of, 216; tym- panum of, 216, 217; Jacob- son’s organ in, 158 Amphiorus, entire animal and tramsverse section of, Fig. 54, 92; as descendant of ancestral] stock of vertebrates, 93; ingestion in, 95; “‘ciliated groove’ of pharynx, 98; mouth of, 129; light cells of, Fig. 96, 183; spinal cord (section), Fig. 96, 183 “Ampulle” of shark, Fig. 6, 13, 16, 204, 206 Anaspida, Fig. 4, 11, 96 Andrews, Roy C., discovery of Cretaceous mammals by, 51 Angular bone, evolution of, Fig. 52, 82; of Trimerorhachis, Fig. 64, 111; of Megalichthys, Fig. 64, 111; of mammal-like reptiles, 218 Animalcule, ‘slipper (Parame- cium), Fig. 1, 5 Anteater, Spiny (Echidna), mouth of, 131 Anthropoid, human dentition de- rived from that of, 57; development of the eye in, 65; face influenced by _ erect posture of, 66; date of man’s 261 INDEX Anthropoid—(Continued) separation from _ primitive, 74; genesis of temporal bone in, 88; lips of, 133; incisors of, 138, 139; affinities of Piltdown canine tooth to that of, 141; difference between human and anthropoid dentition, 141; muzzle of foetus, 142; foetal muzzle compared with that of man, 143; palatal arch of, 143; premolars of, 144; dental formula of man and of, 145; type of milk teeth ancestral to that of man, 149; com- parison of molar teeth with those of man, 146, 149; nasal chambers of, 161; rate of growth of nasal septum, 167; human eye compared with that of, 195; orbital axes of, 196, Fig. 35, 58; external ears of, 214 Antihelix, development of, 212 Antra, of nasal chamber, 162 Arachnids, theory of vertebrates derived from, 7 Arboreal life, all primates passed through stage of, 54; favored development of eye, 55; man bears traces of, 63; skull changes in pro-anthropoids brought about by, 91 Archeozoic era, origin of plant life in, 27 * Arches, visceral,’ 102 Arctocebus, top view of skull, Fig. 35, 58 Aristotle, on physiognomy, 220, 222 Armadillo, foetal, Fig. 114, 221 Articular bone, development of, 112; of Megalichthys, Fig. 64, 111; of Trimerorhachis, Fig. 64, 111; of turtle embryo, Fig. 64, 111 Arthropods, theory of vertebrates derived from branch of, 7; eyes of, 182 Asia, as home of early mammals, Auditory ossicles, of human ear, 202; Fig. 103, 203; Fig. 111, 216; origin of, Fig. 113, 218; of foetal Perameles, Fig. 113, 218; of Cynognathus, Fig. 118, 218; innervation of muscles of, 219; of foetal armadillo, Fig. 114, 221; of foetal hedgehog, Fig. 115, 221; of human embryo, Fig. 115, 221 Auricularia, (larva of sea- cucumber), Fig. 55, 93 Australian aboriginal, skull of (under side), Fig. 53, 85; lower molar of, Fig. 80, 151; nose of, 169 Australopithecus, skull, side view, Fig. 42, 68; Fig. 46, 72; brain of, 72; restoration of, Fig. 47, 73 Autostylic attachment, of primary upper jaw to skull, Fig. 62, 105 Balance, the sense of, 202 Balanoglossus, theory of relation to ancestors of vertebrates, 93; larva of (Tornaria), Fig. 55, 93 Bandicoot, See Perameles Baphetes, under side of skull of, Fig. 53, 85, Fig. 63, 108 Bass, striped, braincase of, Fig. 10, 22 ‘*Becheraugen,”’ Fig. 96, 183 Behavioristic method of study of physiognomy, 224 Behring Straits, as land-bridge for early mammals, 52 Bell, Sir Charles, ‘“‘“Essay on the Anatomy of Expression,” of Amphiozrus, 229 Bichir (Polypterus), 24; embryo of, Fig. 14, 26 Biconjugate, eyes of man and apes, 67, 189; movement not attained by lower primates, 198 Bilateral symmetry, radial symmetry, 6 Binocular, eyes of man and apes, 67; vision in man, 189; not possible in Notharctus, 196; supersedes established in Old World monkeys and _ anthropoid apes, 196 Bipinnaria, larva of starfish, Fig. 55, 93 262 INDEX Birds, inconspicuous during Age of Reptiles, 45; period of dom- inance of, Fig. 25, 46; naso- buccal channel of, 122 Bloodhound, acromegaly in, 231 Bone-cell, in cross-section of skull of fossil ganoid, Fig. 9, 20; as basic element of skull, 21 Bony mask, in Labidosaurus, Fig. 23, 42; sunk beneath skin in mammals, 43 Brachiation, and quickness of vision, 198; and biconjugate movement of eyes, 198 Branchiostegals, elimination of, 114 Brain, rudimentary, of flatworms, 6, Fig. 2, facing 6; of sand- flea, Fig. 2, facing 6; of annelid worms, 6; forebrain of shark, 14; of the tarsier, 53; progressive series in evolu- tion of primate, 63; primates characterized by enlargement of, 64; of chimpanzee, 66; of Australopithecus, 72; skull changes consequent upon en- largement of, 87; enlargement of, in pro-anthropoids, 91; forebrain as olfactory center, 156; foetal growth of, its effect on skull shape, 170; as derived from ectoderm, 179; eyes of vertebrates as out- growths of forebrain, 179; origin of pineal and parapineal organs in tract that became brain tube, 186; visual cortex of, 191; oculomotor nerves of, in chimpanzee and man, 198 Braincase, of shark, Fig. 7, 17; of fish, Fig. 10, 22; as thrust- block, 22; evolution of pri- mate, 63; bony crest on base of, of Seymnognathus, 117 Brain tube, relation of primitive eyes to, 186 Branchial arches, of shark, Fig. 7, 17; constrictors of, Fig. 8, 18; as origin of larynx, tonsils, thyroid and thymus glands, 126 Branchial chamber, loss of bones covering, 89 Branchial skeleton, of man com- pared with that of other vertebrates, 128 Broili, F., contributions to pale- ontology, 86 Broom, R., contributions to pale- ontology, 86 Brown, Barnum, discovery of Eodelphis by, 47 Bryant, W. L., contributions to paleontology, 86 Bulldog, as abnormal animal type, 230 Bursa (meniscus), origin of, 38, 39; Fig. 22, 38 Calamoichthys, 24 Calcium carbonate, in skeleton of shark, 23 Canals, semicircular, circular canals Canine teeth, human, origin of, 90; of primitive man, 76; of human ancestor, well devel- oped, 142; human and an- thropoid, 141; of Piltdown man, 141, 143; alignment of, 144; of cynodonts, 116 Caniniform teeth, 115 Captorhinus, skull of, Fig. 53, 85 Carnivorous ancestors of man, 136 Cartilage, alar, of mammalian nose, 167; growth power of, 170; labial, early form of, 104, of shark, Figs. 7, 8, 17, 18; Meckel’s, see Meckel’s carti- lage; median, of nose, origin of, 167; oral, of sharks and embryo vertebrates, 102; palatoquadrate, of primary upper jaw, 102 Cartilaginous skeleton, of head of shark, Fig. 7, 17 Caruncula, of human eye, Fig. 101, 194 Chapelle aux Saints, La, skull of, see Man, Neanderthal Cheek arch, of Scymnognathus and Ictidopsis, 35, 36 Cheek bone, human, foreshadowed in Mycterosaurus, 34 Cheeks, embryonic development of the, 166 Ceratohyal, of the shark, 18 Cebus, face of, Fig. 34, facing 56 see Semi- 263 INDEX Cephalaspis, Fig. 4, 11; mouth of, Fig. 57, 96 Cephalaspid ostracoderms, Stensié on, 94 Cephalopods, eyes of, 178, 179; development of eye in, Fig. 95, 181 Catarrhine monkeys, see Monkeys, catarrhine Catablema, ocellus of, Fig. 91, 175 Chimpanzee, facial expression of, Fig. 116, facing 222; female and male, Fig. 40, facing 65; female with young, Fig. 39, facing 64; brain of, compared with that of Notharctus and of man, 65, 66; external ear of, Fig. 110, 213, 214; face of, compared with that of early man, 76; hands of, 198; palatal arch of, Fig. 74, 140; incisors of, 138; iris of, 199; jaw muscles of, Fig. 61, 103; lacrymal bone of, 200; lower jaw of, Fig. 45, 71; molar of, Fig. 79, 150; muzzle of, 142; nasal meati and sinuses of, 161; oculomotor nerves of, 198; protrusile lips of old, Fig. 70, 132; skull of, 65 (young), Fig. 102, 197; (fe- male), Fig. 36, 59; (top view), Fig. 35, 58; Fig. 43, 69, (front view), Fig. 44, 70, (under side), Fig. 53, 85; tongue of, 123 “Chimpanzee type” of human ear, Fig. 110, 213 Chin, effect of development of tongue on, 126; of early man, 76 Chlamydoselachus, face of, Fig. 5, facing 12; instruments of pre- cision in head of, Fig. 6, 13; jaw muscles of, Fig. 61, 103; development of teeth of, 109 Choane, in palate of lion pup, Fig. 66, 121; of lizard, Fig. 66, 121; of human embryo, 120, Fig. 66, 121 Chondrocranium, its component parts, 83 Chordate, earliest type of verte- brate, 10; Amphioxrus, most primitive living, Fig. 54, 92 Choroid, of shark, Fig. 99, 192; of man, Fig. 100, 193 Choroid layer, lacking in cephal- opod eye, 180 Cilia, as means of ingestion in Amphioxrus, 95; in ostra- coderms, 95 Ciliary muscles, of eye of shark, Fig. 99, 192; of human eye, Fig. 100, 193 “Ciliated groove” of Amphiorus, Fig. 54, 92; of pharynx of larval lamprey, 98 Circumorbital bones, of the, Fig. 51, 81 Civilization, its effect upon human teeth, 149 Clark, W. E., Le Gros, on evolu- tion of primate brain, 63 Cladoselache, frontispiece Clinical study of physiognomy, 224 Coal measures, see Carboniferous Cochlea, human, development of, Fig. 105, 206; its equivalent first in amphibia, 206; of human ear, Fig. 103, 203; spiral ducts of, Fig. 103, 203 Constrictor muscles of gill arches, 104 Cornea, human, Fig. 100, 193; in shark and man, 193; of molluscan eye, development of, Fig. 95, 181; of shark, Fig. 99, 192 Coronoid bones, of Megalichthys, Fig. 64, 111; of Trimeror- hachis, Fig, 64, 111; of turtle embryo, Fig. 64, 111 Corti, the organ of, Fig. 103, 203, 204 Evolution Cotylosaurian reptiles, see Reptiles Cranial nerve, seventh, 43 Cretinism, cause and effect of, 171 Criminological study of physiog- nomy, 225 Cro-Magnon man, see Man, Cro- Magnon Crossopterygii, related to Carbon- iferous amphibia, 114; com- parison of skull with early Amphibia, 107, Fig. 63, 108; composition of skeleton, 23; characteristics of, 24; living representatives of, 24; dentary 264 INDEX Crossopterygii— (Continued) bone of, 108, 130; maxillae and premaxillae of, 107, 130; mouth of, 130; nearest to direct line of ascent, 26; origin of teeth of, 109; tooth structure of, 112, Fig. 18, following, 30; teeth of, 117; possibly possessed a lung, 24; Eusthenopteron (upper Devo- nian), frontispiece; Fig. 12, facing 23; skull of, under side, Fig. 53, 85; Fig. 63, 108; Megalichthys, lower jaw of, Fig. 64, 111; Rhizodopsis, skull of, Fig, 17, 30; Fig. 48, 78; Osteolepis, cross section of skull, Fig. 9, facing 20; Polyplocodus, teeth of, Fig. 18, following 30; Polypterus, jaw muscles of, Fig. 61, 103; embryo of, Fig. 14, 26 Cruciform pattern of lower molars, 149; Fig. 80, 151 Crustacea, compound eyes of, 178; mouth-legs of, 6 Crus helicis, development of the, 212 Cusps, characteristic of the cheek- teeth of mammals, 145 Cyclostomes, as possible descend- ants of ostracoderms, 98, 186; embryology of the, 186; feed- ing habits of the, 97, 98; lamprey, adult, Fig. 59, 97; lamprey, larval, Fig. 59, 97; mouth-pouches in, Fig. 56, 94; “tongue”’ of, 123; tooth- gems of, (section), Fig. 60, Boe iouts, skulls of, Figs. 48-53, 78-85; dentition of, 115, 116; secondary palate of, 119; comparison of molar teeth with those of man, 145; middle ear of, Fig. 112, 217 Cynognathus, dentition of, Fig. rue 147; middle ear of, Fig. 113, 218; jaw muscles of, Fig. 61, 103; skull of, Fig. 53, 85 Darwin, on the origin of mankind, Dawn man, see Eoanthropus daw- sont Deltatheridium, D. pretrituber- culare, skull and head re- stored, Fig. 29, 50; dentition of, Fig. 77, 147 Dental formula, of the primates, Fig. 37, 61; of man and anthropoids, 145 Dentary bone, its development in mammal-like reptiles, 108; evolution in series from fish to man, Fig. 50, 80; contact with squamosal in mammals, 87; not dominant in crossopts, 108; covered with skin in early amphibia and crossopts, 130; crowded out posterior elements, 36; evolution of, 87; progressive dominance of, 116 of armadillo, foetal, 221 of crossopts, 110, 130 of Ictidopsis, Fig, 21, 37 of Megalichthys, Fig. 64, 111 of Mycterosaurus, 35 of Scymnognathus, 36; Fig. 21,37 of Thylacinus, 36; Fig. 21, 37 of Trimerorhachis, Fig. 64, 111 of turtle, embryo, Fig. 64, 111 Denticles, constitution of shagreen, 100; in skin of ostracoderms, 117 Dentition, evolution of human, Fig. 77, 147; Fig. 78, 148: origin of human, 90; reduced to two sets in cynodonts, 116 Dermal plates (prevomers) of Devonian crossopts, 109 ‘“Derm-bones,” development of, 21; of fossil crossopts, 112 Dermocranium derived from skin, 21; its component parts, 83 Dermo-supraoccipital bone, evolu- tion of, Fig. 49, 79 Development and growth, Stock- ard’s studies of, 172 Development of the human face, Fig. 86, 165; Fig. 87, 166 Diadectes (Permo-Carboniferous), skull of, Fig. 62, 105 Diademodon, dentition of, Fig. 77, 147 Diaphragm, its origin and func- tion, 41; Sir Arthur Keith on the primate d., 63 Fig. 114, 265 INDEX Didelphodus, dentition of, Fig. 77, 147 Didelphys, Fig. 26, facing 46; jaw muscles of, Fig. 61, 103; skull of, Fig. 28, 49; skull compared with Lodelphis, Fig. 27, 48 Diet, changes in diet of primitive man, 75; probable carnivor- ous diet of man’s ancestors, 152; characters of early pri- mates adapted to, 67; of pre- vertebrates, 95; later dietary habits of man, 70 Dinaric type of nose, Fig. 89, facing 170 Dipnoi, modern survivors of, 24; removed from main line of ascent, 25; embryonic devel- opment of, 25; nose of, 157; re- spiration of, 122,157; Dipterus (Devonian), Fig. 13, facing 24 Dipterus (Devonian), Fig. 13, facing 24 Disharmonic types of human face, 237 Dogs, acromegaly in, 231; ateleosis in, 231 Dryopithecus, dentition of, Fig. 78, 148; derivation of human dentition from, 58; lower jaw of, Fig. 45, 71; D. cautleyt, premolars, lower front, Fig. 75, 144; molars, lower, Fig. 79, 150; D. fontani, premolars of, Fig. 75, 144; molars of, Fig. 79, 150; D. fricke, molars of, Fig. 41, facing 66, Fig. 79, 150; D. rhenanus, molars of, Fig. 38, 62; comparison of upper molars with human, 149 ““Dryopithecus pattern,” 149, Fig. 41, facing 66; in teeth of anthropoids, Fig. 79, 150; in teeth of man, Fig. 80, 151 Duchenne, G. B., his study of physiognomy, 223 Dwarf, achondroplastic, nose of, 169; skull of, 230 Ear, evolution of the primate, 63; evolution of auditory ossicles, 215, Fig. 115, 221; innerva- 266 tion of the muscles of, 219; movement of, 133 External ear, of antelope, 211 of bat, 211 of chimpanzee, Fig. 110, 213 of Echidna, 210 of elephant, 211 of gibbon (Hylobates), Fig. TO 2s of gorilla, Fig. 110, 213 of lemur (Lemur catta), 212 of lemuroid (Nycticebus), Fig. 110, 213 of macaque, fcetal, Fig. 109, 212 of mammals, 211 of monkeys, 212 of primates, lower, 57 of orang, Fig. 110, 213 of whale, 211 origin of, Fig. 108, 911; development of, 211; aid in development of man, 202; types of mammalian, 211; function of human, 202; approach to monkey type of fcetal human, 214; “chimpanzee type” of hu- man, Fig. 110, 213; re- semblance of human and anthropoid, 214 Inner ear of alligator, Fig. 104, 205, 207 of frog, Fig. 106, 208 of ganoid (Lepidosteus), Fig. 104, 205 of man, Fig. 103, 203, Fig. 104, 205, Fig. 105, 206 of rabbit, Fig. 104, 205 of reptile, primitive (Hat- teria), Fig. 104, 205; see also Sphenodon of shark (Acanthias), Fig. 104, 205 derivation from ectoderm of, 204; components of, 202, 204; functions of, Fig. 103, 203, 204; evolution of, fish to man, Fig. 104, 205 Middle ear of ancient and modern Am- phibia, 29 of frog, 207; Fig. 106, 208 of mammal-like reptiles, Figs. 112, 113, 217, 218 INDEX Ear— (Continued) Middle Ear—(Continued) of foetal mammal, Fig. 113, 218 of man, Fig. 111, 216 components of, 202; function of, 202; communication with throat of, 208 Ear muscles, reduced in man, 215 Ear drum, see Tympanum Echidna, external ear of, 210; head of, Fig. 23, 42; mouth of, 131 Echinodermata, Auricularia, larva of sea-cucumber, Fig. 55, 93; Bipinnaria, larva of starfish, Fig. 55, 93 Ectoderm, derivation of brain from, 179; of mouth from, 94; of mouth-pouches from, Fig. 56, 94; of inner ear from, 204; origin of eyes of jellyfish in, 174; specialization of cells of, 157 Egg cell, complexity of the fertil- ized, 157 Egyptian, upper incisor of old, Fig. 72, 137 Ehringsdorf man, see Man, Nean- derthal Elasmobranchs, see Sharks, Rays, etc. Embryo, Jacobson’s organ in, Fig. 82, 159; muzzle of, 142; nose of, 162, Fig. 65, 120; palatal region of, Fig. 66, 121; teeth of, 134, Fig. 71, 135; gill-slits of, 127, Fig. 69, 127; fish-like stage of, 122; tongue and larynx of, 126 of Amblystoma punctatum, Fig. 14, 26 of macaque, Fig. 108, 211 of man, Fig. 108, 211 of Perameles, 38, Fig. 22, 38 of Polypterus, Fig. 14, 26 of rabbit, Fig. 56, 94 of sturgeon, Fig. 107, 209 of turtle, Fig. 64, 111 of vertebrates, Fig. 56, 94 Embryonic development of cyclostomes, 186 of Polypterus, 24 of Neoceratodus, 25 Embryology, its evidence on origin of vertebrate eye, 186 Endocrine glands, as producers of hormones, 171 Endocranium, derived from carti- lage, 21 Eoanthropus dawsoni, jaw and teeth ape-like, 72; lower jaw of, Fig. 37, 61; lower jaw of, Fig. 45, 71; left lower molars of, Fig. 38, 62; left lower molars of, Fig. 41, facing 66; skull, side view, Fig. 42, 68 Eocene, mammalian remains from, 53; early placental mammals in, 52; development of eye in primates of, 55; European Adapide from, 54 Eodelphis (Cretaceous), restora- tion of face of, frontispiece; skull compared with Dzidel- phis, Fig. 27, 48; skull compared with WNotharctus, 55; skull of, Fig. 48, 78 Eogyrinus (Lower Carboniferous), Fig. 15, 28; restoration of face of, frontispiece Epipterygoid bone, of Diadectes, Fig. 62, 105 Epipterygoid process, of fcetal salamander, Fig. 62, 105 Epithelial cells, differentiation of, 156 Epithelium, derivation of primi- tive eye from, 176; as origin of parts of the vertebrate eye, 179 Erinaceus, auditory ossicles of embryo, Fig. 115, 221 Eryops, jaw muscles of, Fig. 61, 103 Ethmoid sinus, 162; its connection with nasal meati, Fig. 85, 163 Ethmoidal cartilage, ossification of, 199 Eurypterids, derivation of verte- brates from forms related to, 182 Eustachian tube, of frog, 207; Fig, 106, 208; of man, Fig. 111, 216; in human embryo, 162 Eusthenopteron (Devonian), Fig. 12, facing 23; face of, frontis- piece; skull of, under side, Fig. 53, 85; skull of, under side, Fig. 63, 108 267 INDEX Evolution, proceeds by loss of superfluous parts, 114; of human face, Sir Arthur Keith on, 120; of primates, diver- gent, 57; of the circumor- bital bones, Fig. 51, 81; of human dentition, Fig. 77, 147; also Fig. 78, 148; of the human jaw bones, Fig. 50, 80; of human jaw muscles, Fig. 61, 103; of human skull roof, Fig. 49, 79; of human skull, under side, Fig. 53, 85; of the temporo-mandibular series, Fig. 52, 82; of the vertebrate eye, Fig. 97, 185 Eyes, beginnings of, Fig. 91, 175; biconjugate movement and the oculomotor nerves, 198; ciliary muscles of, 193; cir- cumorbital bones, evolution of the, 88; Fig. 51, 81; clear- ness of vision and the brach- iating habit, 198; correlation of vision with smell, 156; as directional organs, 178, 200; dorsal eyes, Fig. 97, 185, 187, 200; elements of primitive, and their functions, 175; choroid of vertebrate, 188; evolution of vertebrate, Fig. 97, 185; evidence of em- bryology on origin of verte- brate, 186; function of paired, 177; Plate cited on paired eyes of vertebrates, 178; paired eyes essentially an outgrowth of brain, 179; meagre fossil evidence of origin of vertebrate paired eyes, 184; vertebrate and invertebrate, compared, 178, 180, 181; summary of deve- lopment of vertebrate, 200; human, as a camera, 189; development of human eyes favored by arboreal life, 55, 90; function of human, 173; comparison of human, and shark, 192; comparison of human, and anthropoid, 195; position of, inherited from pro-anthropoid stock, 196; pineal and parapineal, Fig. 97, 185, 200; caruncula of human, 194; fundus oculi of human, 199; horizontal sec- tion of, Fig. 100, 193; iris of human and anthropoid, 198; lacrymal glands and canals of human, Fig. 101, 194; macula lutea of human and anthropoid, 199; muscles of human, Fig. 98, 190, 191; of cephalopod mollusca, devel- opment of Fig. 95, 181 of flatworm (Planaria), Fig. 92, 177, Fig. 2, facing 6 of jellyfish (Catablema), Fig. 91, 17 5 of jellyfish (Sarsia), Fig. 91, 175 of Amphioxus, Fig. 96, 183 of deep-sea cephalopods, 178 of crustacea and insects, 178 of flatworms, 6, 176 of Galago, 60 of invertebrates, 174 of advanced lemuroids, 60 of Limulus, 182 of higher mollusca, 178 of Nautilus, 181 of Notharctus, position in, Fig. 35, 196 of Pecten, 178 of Planaria, as _ directional organs, Fig. 93, 178 of Planaria, section, Fig. 92, 177 of pre-chordates, 186 of primates, development of, 65; progressive declination of the, Fig. 36, 59 of protista, 174 of sand-flea (Orchestia), Fig. 2, facing 6 of scorpion, 182 of shark (Chlamydoselachus anguineus), Fig. 6, 18, 15 of shark, horizontal section, Fig. 99, 192 of shark nearer to human than to invertebrate, 191 of squid, section of, Fig. 94, 179 of Tarsius, Fig. 31, facing 58, 60 Eye stalks, formation of the, Fig. 97, 185 Eyeball, muscles of the human, Fig. 98, 190; muscles of the, of shark, Fig. 6, 13, 15 Eyelids, of man, 194; of Sepia, 180 268 INDEX Face, as index of character, 220; changes in arboreal pro- anthropoids, 91; changes in primitive man, 76; embryonic development in mammals, 166; extremes in form and color of, Fig. 90, facing 172; primary functions of the, 3; shape of anthropoid f. con- ditioned by erect posture, 64, 66; Mongolian type, 170; human, of same elements as in gorilla, 91; Sir Arthur Keith on evolution of, 120; three stages in evolution of, 122; Stockard’s classification of the, 232 of young chimpanzee, Fig. 116, facing 222 of chimpanzee, Figs. 39, 40, facing 64, 65, 66, 76 of lemur (Lemur variegatus), Fig. 34, facing 56 of man, see Man, face of of catarrhine monkey (Lasio- pyga pygerythrus), Fig. 34, facing 56 of platyrrhine monkey (Cebus capucinus), Fig. 34, facing 56 of shark Chlamydoselachus, Fig. 5, facing 12 Facial armor of Osteolepis, Fig. 11, facing 22 Facial expression, methods for the study of, 223-5 Facial muscles, of Echidna, Fig. 23, 42 of gorilla, Fig. 23, 42 of Labidosaurus, Fig. 23, 42 of man, Fig. 23, 42 of Sphenodon, Fig. 23, 42 Facial nerve, chief branches of, Fig. 24, 44; original territory of the, 132 Features, inheritance of individ- ual, 236 Feeding habits of some Amphibia, Feet, correlated use of, in Pri- mates, 64; evolution of pri- mate, 63 Fishes, lobe-finned, ancestral to land vertebrates, 26; com- parison of skull with that of amphibian, 29; theories of origin of, 7, 8, 92, 93; ears of primitive, 204; jaws of, prim- ary, 104; jaw muscles and jaws of, 104-6; lateral line organs of, 206; man owes ground-plan of face to early, 89; methods of ingestion of, 104; resemblance of human embryo to, 122; shoulder girdle of, compared with that of early amphibia, 28 Crossopterygii bony plates on primary jaws of, 106; Fig. 12, facing 23; chemical composition of skeletion of, 23; structure of teeth, 112; Fig. 18, following 30 Eusthenopteron, Fig. 12, fac- ing 23; face of, frontispiece; skull of, under side, Fig. 53, 85; skull of, under side, Fig. 63, 108 Osteolepis, skull of, top view, Fig. 11, facing 22; cross section of skull, Fig. 9, fac- ing 20 Polyplocodus, teeth of, Fig. 18, following 30 Polypterus, jaw muscles of, Fig. 61, 103; embryo of, Fig. 14, 26 Rhizodopsis, skull of, Fig. 17, 30; skull of, side view, Fig. 48, 78; skull, roof of, Fig. 49, 79 Dipnoi (Dipneusti) Dipterus, the nose of, Fig. 13, facing 24, 157; respiration of, 122 Elasmobranchii, see Shark, pas- sim Ganoidei, skeleton, composition of, 23 Flatworm (Planaria), Fig. 2, facing 6; apparently descend- ant of jellyfish group, 5; eyes of the, 176, Fig. 92, 177, eyes as directional organs in the, Fig. 93, 178; illustrates evolution of primitive head, 6, Fig. 2, facing 6 Foot, of tree-grasping type in all primates, 54 Fore-brain, as olfactory center, 156 269 INDEX Forests of the Devonian period, 27 ‘Fossil, living,’’ opossum as a, 47 Fovea anterior, 149; in molar of Ehringsdorf man, Fig. 80, 151 Fovea posterior, 149 Frog, development of ear in, 207; Eustachian tube of, 207; head of, transverse section of, Fig. 106, 208; stapes of, 216 Frontal bones, 83; become one of dominant elements in vault of human skull, 87; evolution shown in series of ten skulls from fish to man, Fig. 49, 79; joint process of frontal and malar replaces reptilian post- orbital bones, 90; their rela- tion to superior maxillary in mammals, 87; retained from fish to mammals, 86; sinus of, 161 of chimpanzee, female, Fig. 49, 79 of Didelphys, 50; Fig. 49, 79 of Ictidopsis, Fig. 49, 79 of man, Fig. 49, 79 of Mycterosaurus, Fig. 49, 79 of Notharctus, Fig. 49, 79 of Seymouria, Fig. 49, '79 Frontal sinus, its connections with nasal meati, Fig. 85, 163 Fundus oculi in man and anthro- poids, 199 Galago, eye and orbits of, 60 Ganoids, possessed a lung, 24; skull compared with that of amphibian, 29, 107; com- position of skeleton, 23; mouth of, 130; relation to human ancestry, 24; hyoid gill cleft in, 209; teeth of earliest amphibia similar to those of, 31 Ganoine, 23; covers bony jaw- plates of higher fishes and early amphibia, 106; on max- ille and premaxille of early crossopts, 130; on teeth of fossil crossopts, 112 Gaupp, E., cited on the origin of the meniscus, 38 Genetic study of physiognomy, 224 Genioglossus, see Geniohyoglossus muscle Geniohyoglossus muscle, of gorilla, Fig. 67, 124; of man, Fig. 67, 124; Fig. 68, 125, 126 Gibbon (Hylobates) external ear of, Fig. 110, 213; habit of climbing upright, 64; hands of, 198; palatal arch of female, Fig. 74, 140; skull of, top view, Fig. 35, 58 Gidley, W., on mammalian teeth from Basal Eocene, 53 Gigantism and acromegaly in dogs, 231 Gill arches, see Branchial arches Gill cartilages, folding of, in shark, 123 Gill chamber, bony covers of the, 23; changes of, from crossopts to Amphibia, 29 Gill clefts, in embryo sturgeon, Fig. 107, 209 Gills, internal, eliminated by Amphibia in adult stage, 114 Gill openings, homologous with mouth-pouches, 94 Gill region of Cephalaspis (restored by Stensio), Fig. 57, 95 of Kieraspis, Fig. 57, 95 Gill slits, in human embryo of third week, Fig. 69, 126, 127 Glands, endocrine, as producers of “hormones,” 171; hypo- physis, 230; hypophysis- pituitary complex, 231; lacry- mal, human, 194; Meibomian, in human eyelids, 194; pineal and parapineal, 186, 200; pituitary, effect of diseased, 171; salivary, of man and apes, 129; sebaceous, origin and function of, 41; sudori- parous, origin and function of, 41; thyroid, and gigan- tism, 231; effects of deficient, 171; effects of deranged, 237; effect on growth of face, 232 “Goblet eye”’ of flatworm, section of, Fig. 92, 177; of jellyfish (Sarsia), Fig. 91, 175 Goniale, of armadillo, foetal, Fig. 114, 221; of hedgehog (Erin- 270 INDEX Goniale— (Continued) aceus) foetal, Fig. 115, 221; of human embryo, Fig. 115, 221 Gorgonopsian reptiles, see Reptiles Gorilla, external ear of, Fig. 110, 213,214; facial muscles of, Fig. 23, 42; facial nerve of, Fig. 24, 44; hands of, 198; head, longitudinal section, Fig. 67, 124; lacrymal bone, 200; lachrymal bone of feetal, 199; nose of, 164, 170; nose of, foetal, Fig. 84, 161; palatal arch of male, Fig. 74, 140; nasal meati and sinuses of, 161; skull compared with Piltdown, 143; skull of young g., front view, Fig. 102, 197; teeth foreshadow “shovel shaped”’ incisors, 138; teeth, lower molar, Fig. 79, 150; teeth, canine, resemblance to Piltdown, 141; central incisors of young, Fig. 72, 137; milk teeth of young, Fig. 76, 146; tongue of young, 123 Gregory, William K., his con- tributions to paleontology, 86; places separation of man and anthropoids in Lower Miocene, 74; on hind-feet of primates, 54; “Origin and Evolution of the Human Dentition,” 146 Gregory, William K., and Milo Hellman, 146; “The Denti- tion of Dryopithecus and the Origin of Man,” 146 Gregory, William K., and Simpson, G. G., describe Cretaceous mammals, 51 Growth, glandular factors affect- ing, 237; mechanism of, 172; stimulation of, by “hor- mones,’ 171; types of, in man, Fig. 117, 232 Gular plates, elimination of, Fig. 17, 30; also 114 Hagfishes (Cyclostomata), com- pared with ostracoderms, 97; ostracoderms ancestral to, 10; tongue of, 123 Hair, origin and function of, 41; possibly possessed ky mam- mal-like reptiles of Trias, 42 Hands, correlated use of eyes, hands and feet, by primates, 64; evolution of primate, 63; progressive changes of, 198 Hatteria, labyrinth of, Fig. 104, 205 Hatteria, see also Sphenodon Haughton, S. H., his contributions to paleontology, 86 Head, evolution of primitive, Fig. 2, facing 6; inheritance of head shape, 236; nature and function of, 12; of arachnids, 7 of Australopithecus, Fig. 47, facing 73 of Deltatheridium, restored, Fig. 29, 50 of Echidna, Fig. 23, 42 of flatworm (Planaria), Fig. 2, facing 6 of frog, transverse section, Fig. 106, 208 of gorilla, young, longitudinal section, Fig. 67, 124 of Labidosaurus, Fig. 23, 42 of lamprey, larval, longitudinal section, Fig. 56, 94 of man, longitudinal section, Fig. 67, 124 of man, embryo, third week, Fig. 69, 127 of ostracoderms, 11 of rabbit, longitudinal section, Fig. 56, 94 of sand-flea (Orchestia), Fig. 2, facing 6 of shark, cartilaginous skeleton of, Fig. 7, 17 of shark, dissection of, Fig. 81, 155 of shark (Chlamydoselachus), Fig. 5, facing 12 of shark (Chlamydoselachus), diagram, Fig. 6, 13 of Sphenodon, Fig. 23, 42 of Zalambdalestes lechei, re- stored, Fig. 29, 50 Hearing, the mechanics of, 204 restored, Hedgehog (Erinaceus) feetal, auditory ossicles of, Fig. 115, 221 Heidelberg man (Homo _ heidel- bergensis), chin of, 72; lower Q71 INDEX Heidelberg man—(Continued) jaw of, Fig. 37, 61; Fig. 45, 71; lower molar of, Fig. 80, 151; teeth of, 143 Helix, development of, 212 Hellman, Milo and William K. Gregory, ““The Dentition of Dryopithecus and the Origin of Man,” 146 Herbivorous vertebrates, could not have given rise to carniv- orous forms, 101 Heredity, the shape of the head, 236; and the shape of the nose, 172 Hesse, on the primitive eye, 176 Hindu, lower molar of, Fig. 80, 151 Hittite, type of nose, 169; Fig. 89, facing 170 Homo heidelbergensis (Heidelberg man), chin of, 72; lower jaw of, Fig. 37, 61; Fig. 45, 71; lower molar of, Fig. 80, 151; teeth of, 143 Homo neanderthalensis, lower jaw of, Fig. 45, 71; left upper and lower molars of, Fig. 38, 62 Homo neanderthalensis (La Chap- elle aux Saints), skull of, side view, Fig. 42, 68; skull of, top view, Fig. 43, 69; skull of, front view, Fig. 44, 70 Homo neanderthalensis (Ehrings- dorf), central incisors of, Fig. 72, 137; lower jaw of, Fig. 45, 71; lower molar of, Fig. 80, 151; lower front premolars of, Fig. 75, 144 Homo neanderthalensis (Le Mous- tier), dentition of, Fig. 78, 148; characters of teeth of, Fig, 45, 71, 72; central incisors of, Fig. 72, 137; lower molar of, Fig. 80, 151; palatal arch of, Fig. 74, 140 Homo sapiens, see Man Hooton, Earnest A., his work on inheritance, 236 Hormones, the function of, 171 Hottentot, male, the face of, Fig. 90, facing 172 Hrdliéka, Ales, on incisors of anthropoids and monkeys, 138 Huber, Ernst, on facial muscles, 44, 132 Human characters, point at which primates assumed, 64 Human Dentition, Evolution of the, Hig: 77, 147; Kigaiva: 148 Human Ear, Evolution of the, Fig. 104, 205 Human Circumorbital Bones, Evolution of the, Fig. 51, 81 Human Temporomandibular Series, Evolution of, Fig. 52, 82 Human Face, Development of the, Fig. 86, 165; Fig. 87, 166 Stockard’s classification of the, 232 Human Jawbones, Evolution of the, Fig. 50, 80 Jaw muscles, Evolution of the, Fig. 61, 103 Nose, Embryonic stages of the, Fig. 65, 120 Skull roof, Evolution of the, Fig. 49, 79 Human types, abnormal, studies of, 229 Humor, vitreous, 188 Hunter, John I., on evolution of primate brain, 63, 198 Huxley, T. H., his views con- firmed, 51 Hydroids, effect of ultra-violet rays on, 174 Hylobates, external ear of, Fig. 110, 213; skull of, top view, Fig. 35, 58; male, palatal arch of, Fig. 74, 140 Hyoid arch, of man homologous with that of primates, 128; primary upper jaw suspended from, 104; stapes derived from, 215; cartilage, of Echidna, 210; gill pouch, ear derived from, 208 Hyoid, of shark, Fig. 7, 17 Hyomandibular cartilage, _ of shark, Fig. 62, 105; Fig. 7, 17; Fig. 8, 18 Hyostylic attachment, of jaw in shark, Fig. 62, 105 Hypophysis of larval lamprey, Fig. 56, 94 Hypophysis-pituitary complex, in acromegaly, 231 272 INDEX Ictidopsis, dentary of, Fig. 21, 37; restoration of face of, frontis- piece; skull of, Fig. 20, 35; Fig, 28, 49; Fig. 48, 78 Incisors, of anthropoids and monkeys, 138; mammille on, 136; Fig. 72, 137; of chimpan- zees, 138; of cynodonts, Fig. 50, 80, 116; central, of gorilla, Fig, 72, 137; of Neanderthal man (Le Moustier), Fig. 72, 137; of Neanderthal man (Ehringsdorf), Fig. 72, 137; of old Egyptian, Fig. 72, 137; of white boy, Fig. 72, 137; upper central, of man, three types of, 138; Fig. 73, 139; “shovel-shaped,” of the Krapina race, Mongolians and Indians, 138; retreat of human, 144; of fossil man, 143; origin of, 90 Incus, human embryo shows origin of, 220 of armadillo, fcetal, Fig. 114, 221 of Cynognathus, Fig. 113, 218 of hedgehog (Erinaceus), foetal, Fig. 115, 221 of man, Fig. 111, 216 of man, fetal, Fig. 115, 221 of Perameles, fcetal, Fig. 113, 218 Indians, ‘‘shovel-shaped”’ incisors of, 138 Indrodon, left upper molar of, Fig. 38, 62 Infusoria, effect of ultra-violet rays on, 174 Inheritance, of individual char- acters, 236 Insectivores, ancestors of man were, 52 Insectivorous dentition, traces of, in early primates, 57 Insects, compound eyes of, 178 Interarticular disc, formation of, in Perameles, Fig. 22, 38 Interoperculum, elimination of, Fig. 17, 30, 114 Interorbital space, in advanced lemuroids, 60 Interparietal bones, retained from fish to man, 86 Intertemporal bone, its changes from fish to man, Fig. 49, 79; loss of, in reptiles, 89; re- duction of, 88 Invertebrates, well established be- fore vertebrates, 8; eyes of, 173; eyes compared with ver- tebrate, 178; eyes of higher, 178 Iris, of man, Fig. 100, 193; of mollusca, development of, Fig. 95, 181; of Sepia, 180; of shark, Fig. 99, 192 Jacobson’s organ, description of 158; in man, feetal, Fig. 65, 120; Fig. 82, 159 Jaw, conclusions from history of the, 152; elements traced from earliest Amphibia to man, 107; evolution of the bones of the, 87; Evolution of the Human, Fig. '50, 80; evolution of the primate, 63; mammalian joint of, its formation, 39; the interartic- ular disc in (Perameles, foetal), Fig. 22, 38; its elements homologous in crossopts and early Amphibia, 107; laby- rinthodont method of attach- ment of teeth in, 112; points of advancement in crossopt jaws, 113; prognathous jaws and shape of nose, 170; Fig. 89, facing 170; primate, tabular history of, Fig. 37, 61; origin uncertain below ostracoderms, 101; of dipnoan fishes, 25; of fossil ganoids, 23; of Osteolepis, Fig. 11, facing 22; architecture of “‘visceral arches,” 104; pro- gressive changes associated with development of mus- culature of, 116; of shark nearer to those of man than to invertebrate, 102; special- ized jaws of some Amphibia, 115 Primary, completely masked by secondary jaws in_ higher vertebrates, 104, 106; of crossopts, 106, 110, 113; of higher fishes and early Am- phibia, covered with ganoine- coated bony plates, 106; of 273 INDEX Jaw—(Continued) Primary—(Continued) shark, 106, Fig. 7, 17; Fig. 8, 18; of primitive sharks, 109; of lower primates, in relation to eyes, 60; buds of, in hu- man embryo, Fig. 69, 127 Primary Upper, elimination of teeth in, 115; methods of attachment of, 104, Fig. 62, 105; palatoquadrate cartilage, 102; traces of, in mammalian embryo, 106; retained teeth in Amphibia, 115; of Baphetes, Fig. 63, 108; of Devonian crossopts, 109; of Eusthenop- teron, Fig. 63, 108 Primary Lower, coronoid bones of, in crossopts, 110; develops into articular bone, 112; Meckel’s cartilage, 102 Secondary, definition and de- scription, 107; elements of the, 107; shows unity of origin of higher vertebrates, 107: in sharks, represented only by skin, 106 of armadillo, fcetal, relation of ossicles to, Fig. 114, 221 of crossopts, 109; also 113 of Dryopithecus, section of, Fig. 45, 71 of Eodelphis, Fig. 27, 48 of Leipsanolestes siegfriedti, Fig. 37, 61 of man, influenced by size and function of tongue, 126 of man, longitudinal section, Fig. 68, 125 of man, Cro-Magnon, section of, Fig. 45, 71; Ehrings- dorf, section of, Fig. 45, 71; Heidelberg, section of, Fig. 45, '71; Neanderthal, section of, Fig. 45, 71; Piltdown, Fig. 41, facing 66, 142; Piltdown, section of, Fig. 45, 71 of Megalichthys, Fig. 64, 111 of monkey, longitudinal sec- tion, Fig. 68, 125 of Mycterosaurus, 34 of Pelycodus trigonodus, Fig. 37, 61 of Seymouria, 32 of Trimerorhachis, Fig. 64, 111 Jaw muscles of Chlamydoselachus, Fig. 61, 103; also Fig. 8, 18 of Cynognathus, Fig. 61, 103 of Didelphys, Fig. 61, 103 of Eryops, Fig. 61, 103 of fishes, their evolution, 104 of man, evolution of, Fig. 61, 103 of Notharctus, Fig. 61, 103 of chimpanzee, Fig. 61, 103 of Polypterus, Fig. 61, 103 of Scymnognathus, Fig. 61, 103 of shark, their derivation, 104 Jellyfish, mouth of the, 4, 5; eyes of, 174; eye of, (Sarsia), section of, Fig. 91, 175; Tessera, Fig. 1, 5 Jugal bone (malar), 83; series of skulls showing evolution of, Fig. 51, 81; Fig. 53, 85; joint process of frontal and malar replaces reptilian postorbital, 90 Karroo (Africa), mammal-like reptiles of, Fig. 20, 35-36 Keel bone, see Parasphenoid bone Keith, Sir Arthur, on the develop- ment of the human ear, 212; his studies of abnormal human types, 229; ‘“‘Mor- phology and Embryology,” 157; on the primate dia- phragm, abdomen and pelvic floor, 63; his study of growth, 237; on the evolution of the human face, 120; on the hind feet of primates, 54 Kiaer, J., on ostracoderms, 10 King crab (Limulus), 7 Kinsfolk, Some of Our Earliest, Fig. 4, 11 Krapina race (Neanderthal), “shovel shaped”’ incisors of, 138 Labial cartilages, of shark (Chlamydoselachus), Fig. 6, 13; Fig. 7, 17; Fig. 8, 18; 130 Labidosaurus, head of, Fig. 23, 42 Labyrinth, embryonic develop- ment of, 204 of alligator, Fig. 104, 205 274 INDEX Labyrinth—(Continued) of ganoid (Lepidosteus), 104, 205 of man, 202; Fig. 103, 203, Fig. 104, 205, Fig. 105, 206 of rabbit, Fig. 104, 205 of reptile (Hatteria) (Sphenodon) Fig. 104, 205 of shark (Acanthias), Fig. 104, 205 Labyrinthodont, attachment of teeth, 112; pattern in teeth of fossil crossopts, Fig. 18, following 30, 112; teeth of Devonian fish (Polyplocodus), Fig. 18, following 30; traces in teeth of Seymourza, 118 Labyrinthodonts, teeth of the, 113, 115 Lacrymal apparatus of human eye, Fig. 101, 194 Lacrymal bone, 83, 194; develop- ment of, 199; relation to superior maxillary and jugal in mammals, 87; series of ten skulls showing evolution of, Fig. 51, 81; similar in man and anthropoids, 199; sur- vives in man, 88 Lacrymal glands and canals in ‘human eye, 194 Lacrymal sac, in human eye, 194 Lagena, of alligator, Fig. 104, 205 Lampreys (Cyclostomata), ostra- coderms ancestral to, 10; compared with ostracoderms, 97; adult, Fig. 59, 97; embry- ology of, 186; feeding habits of, 98; mouth of adult, 129; tongue of, 123; section of tooth germ of, Fig. 60, 99; “ciliated groove” of pharynx (Ammocetes stage), 98; longi- tudinal section of larval, Fig. 59, 97; mouth of larval, 129; mouth pouches in larval, Fig. 56, 94 Lanarkia, shagreen denticles of, 100; teeth represented by denticles, 117 Lancelet, see Amphiorus Laryngeal complex, of man and other vertebrates, 128 Larynx, in human embryo, 126; Fig. origin in branchial arches, 126 Lasiopyga kolbi, side view of skull, Fig. 36, 59 Lateral line organs of fishes, 206 Lateral type, in man, Fig. 117, 232; result of crossing with linear, 237 “Lateral line,” of Stockard, Fig. 118, 234 Le Double, his work on lacrymal bone, 199 Legs, hind, of the tarsier, 53; Fig. 31, facing 53 Leipsanolestes, left lower molar of, Fig. 38, 62; jaw of, Fig. 37, 61 Lemur, African (Arctocebus), top view of skull, Fig. 35, 58 Lemur (Lemur catta), ears of, 212; face of, 56; Fig. 34, facing 56; L. variegatus, face of, Fig. 34, facing 56; olfactory sense of, 196; rhinarium of, 56 Lemuroids, eyes of advanced, 60; Adapis (Eocene) skull of, under side, Fig. 53, 85; Notharctus, skull, side view, Fig. 36, 59; Notharctus, skull, top view, Fig. 35, 58; hands of, 198; orbital axes of, Fig. 35, 58, 196; Nycticebus, ex- ternal ear of, Fig. 110, 213; Pelycodus, left upper and lower molars of, Fig. 38, 62; jaw of, Fig. 37, 61; Pro- pithecus, restoration of face of, frontispiece Lens, in eye of Sepia, 180; lens, in development of molluscan eye, Fig. 95, 181; formation of the, in vertebrate eye, Fig. 97, 185, 187; in eye of man, Fig. 100, 193; in eye of shark, Fig. 99, 192 “Light cells,” of the primitive eye, 175, 176; Fig. 91, 175; of Am- phiorus, Fig. 96, 183 Limulus, 7; eyes of, 182; Patten derives vertebrates from relatives of, 92 Lindsay-Johnson, his work on the fundus oculi, 198 Linear type of human growth, Fig. 117, 232; results of cross- ing with lateral, 237 275 INDEX Lips, embryonic development of the, 166; origin and evolution of human, 129; mammalian, their most distinctive feature, 131; philtrum of, 133; of anthropoids, 133; of old chim- panzee, Fig. 70, facing 132; of Lemur, 56, Fig. 34, facing 56; of catarrh in monkeys, 56, Fig. 34, facing 56; of platyrrhine monkeys, 56, Fig. 34, facing 56; of lower prim- ates and man, 133; of Spiny Ant-eater, 131; uses of pro- trusile, 133; muscles of, their importance to newborn mam- mal, 133, 134 Lizard, palate of, Fig. 66, 121 Lobe-finned fishes (see also Cros- sopterygii, Fishes), Eusthe- nopteron, Fig. 12, facing 23, Fig. 53, 85, Fig. 63, 108; Osteolepis, Fig. 11, facing 22, Fig. 9, facing 20; Poly- plocodus, Fig. 18, following 30; Polypterus, Fig. 14, 26, Fig. 61, 103; Rhizodopsis, Fig. 17, 30, Fig. 48, 78, Fig. 49, 79 Lobule, development of the, 212 Locomotion, of primitive man, changes in, 75; skull changes related to habits of, 88 Loxomma allmani_ (Carbonifer- ous), skull of, Fig. 16, facing 28; teeth of, Fig. 18, following 30 Lung-fishes (Dipnoi), (Dipneusti), embryonic development of, 25; modern survivors of, 24; the nose of, 157; Neoceratodus, 25 Luschan, F. v., his work on in- heritance, 236 Macaque, embryo of, Fig. 108, 211; external ear of, Fig. 109, 212 *Macula lutea,” in man and apes, 199 Malar bone (Jugal), series of skulls showing evolution of, Fig. 51, 81, 83, Fig. 53, 85; joint process of frontal and malar replaces reptilian post- orbital, 90 Malleus, human embryo shows origins of, 220 of armadillo, foetal, Fig. 114, 221 of Cynognathus, Fig. 113, 218 of man, Fig. 103, 203 of man, Fig. 111, 216 of man, feetal, Fig. 115, 221 of Perameles, fcetal, Fig. 113, 218 Mammals, appear in large num- bers at the close of the Age of Reptiles, 52; their condi- tion during the Age of Reptiles, 45; some early m. believed related to Platypus, 47; body temperature of, 40; origin of the, 40; period of dominance of, Fig. 25, 46; type of primitive, Fig. 27, 48; cusps characteristic of cheek teeth of, 145; the ear of, 207, 211; face of, its embryonic development, 166, facial muscles of, their origin, 43, 132; Jacobson’s organ in primitive, 158; jaw, embry- onic traces of primary upper, 106; jaw, upper, of m., Fig. 50, 80, 87; method of respira- tion, 119; nasal chamber of, 158; palatal regions of, 119, Fig. 52, 82, Fig. 53, 85; their forerunners from Mongolia, 51; Fig. 29, 50; early placental from New Mexico, 52; tongue of, 123; teeth of triconodont m., 136 ‘“Mammalian joint,” see also In- terarticular disc, 87, 90; for- mation of, 39; development of dentary and squamosal bones to form, 108, 109 of Ictidopsis, Fig. 21, 37 of Perameles, foetal, Fig. 22, 38 of Scymnognathus, Fig. 21, 37 of Thylacinus, Fig. 21, 37 Man, Darwin on the origin of, 65; his debt to the Amphibia, 89; possibility of his existence derives from the Amphibia, 32; unspecialized Amphibia nearest to line of ascent, 115; relation of ganoids to his ancestry, 24; nearer to shark than shark to invertebrates, 14, 102; a hiatus in his 276 INDEX Man—(Continued) history in Pliocene, 70; his ancestors not large ferocious animals, 20; his ancestors small, long-snouted, insec- tivorous - carnivorous mam- mals, 52; probable carnivor- ous diet of the earlier an- cestors of man, 152; om- nivorous - carnivorous diet habits later developed, 70; derived from _ frugivorous proto-anthropoids, 69; changes in diet of primitive man, 75; gradual modification of structure of, 84; structural changes incident to changes of habit, 75; bears stamp of arboreal ancestors and later bipedal adaptation, 63; com- pared with chimpanzee and Notharctus, 65; converges in past to common source with anthropoids, 74; date of his separation from early an- thropoids, 74; several types of, in early Pleistocene, 73; period of dominance, Fig. 25, 46; linear and lateral types of, Fig. 117, 232; some racial types compared, 76; source of the amelioration of his features, 153; m. and primate, characters of, 67; develop- ment, of, aided by eyes and ears, 202; branchial skeleton homologous with primate, 128; “‘gill slits” of embryo, 126 Ear (of man), external, chim- panzee type of, Fig. 110, 213; of foetal m., Fig. 109, 212 Ear (of man), middle, Fig. 111, 216; auditory ossicles, Fig. 115, 221 Ear (of man), internal, Fig. 103, 203; labyrinth of, Fig. 104, 205, Fig. 105, 206 Ear muscles, reduced, 215 Eye (of man), owes develop- ment to earliest primates, 90; anthropoid and human, com- pared, 195; of shark and man compared, 192; horizontal section of, Fig. 100, 193; iris of, 199 2 Embryo (of man), Fig. 69, 127, Fig. 108, 211; Face (of man) of Armenian, Fig. 89, facing 170 of Bushman, South Africa, Fig. 89, facing 170 of Hottentot woman, Fig. 90, facing 172 of pygmy, African, Fig. 89, facing 170 of Roman athlete, frontispiece of Nordic Swede, Fig. 90, facing 172 of Tasmanian, frontispiece of Tyrolese, Fig. 89, facing 170 Facial muscles, origin of the, Fig. 23, 42 Facial nerve, the Fig. 24, 44 Foot derived from _ grasping type, 55 Head, longitudinal section, Fig. 67, 124 Jaws (of man), primary jaws completely masked by second- ary, 106; traces of primary upper j. in embryo, 106; can be traced from earliest Am- phibia to m., 107; Fig. 50, 80; Fig. 53, 85; owes plan of upper and lower j. to mam- mal-like reptiles and earliest mammals, 40; lower jaw of, Fig. 37, 61; origin of zygo- matic arch, 89; dominance of superior maxilla in man, 89; jaw muscles in, Fig. 61, 103; muzzle of chimpanzee and man compared, 142 Nose (of man), Jacobson’s organ lacking or vestigial in, Fig. 65, 120; kinship of man and anthropoids as shown by external nose, 163; nasal profiles, Fig. 88, 168; develop- ment of, 162; of foetal man, Fig. 84, 161; development of nose in fctal man, 162; olfactory pit in fcetal man, Fig. 65, 120; Jacobson’s organ in foetal man, Fig. 65, 120, Fig. 82, 159 Palate (of man), comparative Anatomy of the Human, Fig. rir INDEX Man—(Continued) Palate (of man)—(Continued) 66, 121; palatal arch (of white), Fig. 74, 140; develop- ment of palatal region in embryo, Fig. 65, 120; in em- bryo, sixth week, Fig. 66, 121 Skull (of man), side view, Fig. 36, 59, Fig. 48, 78, Fig. 49, 79, Fig. 50, 80, Fig. 51, 81; front view, Fig. 44, 70; longi- tudinal section, Fig. 83, 160; top view (Cro-Magnon), Fig. 43, 69 Teeth (of man), origin of his dentition, 90; difference be- tween human and anthropoid, 141; traces of derivation of teeth from Dryopithecus and Sivapithecus, 58; Dentition of, Fig. 78, 148; “Dryopithecus pattern” in teeth of, Fig. 80, 151; his teeth and his diet, 57; dental formula of an- thropoids and man, 145; development of, in embryo, 134, Fig. 71, 135; fovea anterior and posterior, 149; derived from anthropoids with well-developed canines (Re- mane), 142; front teeth of, 136; incisors of, 138; incisors, central, of white boy, Fig. 72, 137; incisors, central, of an- cient Egyptian, Fig. 72, 137; incisors, three types of, Fig. 73, 139;incisors, upper central, kinship of man and anthro- poids as shown by, 139; milk teeth of, Fig. 76, 146; milk teeth of, as derived from anthropoid type, 149; kinship of human and anthropoid lower molars, 146; compari- son of molars with those of cynodonts, 145; identity of human and anthropoid molar patterns, 69; molar, lower, of Australian aborigine, Fig. 80, 151; molar, lower, of white man, Fig. 80, 151; history of upper and lower premolars and molars, 146; premolar, lower front, Fig. 15, 144 278 Cro-Magnon, highbred type of skull of, 73; lower jaw, sectioned, Fig. 45, 71; skull of, side view, Fig. 42, 68; skull of, top view, Fig. 43, 69 Ehringsdorf, see Man, Nean- derthal (Ehringsdorf) Heidelberg, chin of, 72; lower jaw of, Fig. 37, 61, Fig. 45, 71; teeth of, 143; lower molar of, Fig. 80, 151 Neanderthal, teeth of, 143 Neanderthal (La Chapelle-aux- Saints), skull of, front view, Fig. 44, 70; skull of, side view, Fig. 42, 68; skull of, top view, Fig. 43, 69 Neanderthal (Ehringsdorf), low- er jaw of, Fig. 45, 71; central incisors of, Fig. 72, 137; lower front premolars of, Fig. 75, 144; lower molar of, Fig. 80, 151 Neanderthal (Krapina),“‘shovel- shaped ”’ incisors of, 138 Neanderthal (Le Moustier), central incisors of, Fig. 72, 137; palatal arch of, Fig. 74, 140; dentition of, Fig. 78, 148; characters of teeth of, Fig. 45, '71, 72 Piltdown, see Eoanthropus Rhodesian, skull of, side view, Fig. 42, 68; nose of, 72 Talgai, skull of, side view, Fig. 42, 68; prognathism of, 72 Trinil, see Pithecanthropus Marmoset (Midas), skull of, Fig. 35, 58 Marsupials, relation to early mam- mals of, 47, 51; Jacobson’s organ in, 159; nasal septum in, 167; skull of, Fig. 53, 85 Mask, bony, of ganoids, 23; Fig. 11, facing 22; of earliest Amphibia, 31; of reptiles, 43; of mammal-like reptiles, 36; of primitive living mammals, 43; starting-point of all cranial bones, 28; covered by facial and jaw muscles, 51 Mastiff, acromegaly and gigantism in, 231 INDEX Matthew, W. D., contributions to paleontology, 86; Eodelphis named by, 47; evidence for conclusions on ancestry of placental mammals, 51 Mazxille, series of ten skulls show- ing their evolution, Fig. 50, 80 Rhizodopsis Paleogyrinus Seymouria Mycterosaurus Scymnognathus Ictidopsis Didelphys Notharctus Chimpanzee, female an covered with skin in early Amphibia, and reptiles, 130; unite with premaxille in anthropoids and man, 87; origin of, in crossopts, 130 of Baphetes, Fig. 63, 108 of Eusthenopteron, Fig. 63, 108 of Seymouria, 32 Maxilla, inferior, development in late mammal-like reptiles, 90; ascending ramus forms mam- malian joint with the squa- mosal, 87 of chimpanzee, Fig. 45, 71 of Cro-Magnon man, Fig. 45, 71 of Dryopithecus, Fig. 45, 71 of Heidelberg man, Fig. 45, 71 of Neanderthal man (Ehrings- dorf), Fig. 45, 71 of Neanderthal man (Le Mous- tier), Fig. 45, 71 Maxilla, superior, homologous in crossopts and early Am- phibia, 107; evolution of, 87; position of, 107; series show- ing evolution of, Fig. 53, 85; dominance of, in man, 89; in achondroplasia, 230; of cynodonts, secondary palate derived from, 119; of mammal-like reptiles, Fig. 50, 80; of mammals, Fig. 50, 80, 87 of Adapis, Fig. 53, 85 of Baphetes, Fig. 53, 85 of Captorhinus, Fig. 53, 85 of chimpanzee Fig. 53, 85 of Cynognathus, Fig. 53, 85 of Eusthenopteron, Fig. 53, 85 of man, Fig. 53, 85 of Mycterosaurus, 34 of Scymnognathus, Fig. 53, 85 of Seymouria, Fig. 53, 85 of Thylacinus, Fig. 53, 85 McGregor, J. H., restorations of primitive man by, 143 Meati, nasal, 161, 162 * Meckel’s cartilage, as primary lower jaw, 102; articular bone develops from, 112; of arma- dillo, foetal, Fig. 114, 221; of Devonian crossopts, 110; of shark, Fig. 6, 13, Fig. 7, 17, Fig. 8, 18, 106 Median cartilage (of nose), origin of, 167; growth of, in orang, 169 Megalichthys, lower jaw of, Fig. 64, 111 Meibomian glands, in human eye- lid, 194 Melanesians, noses of, 169 Meniscus, of mammalian joint, in Perameles, Fig. 22, 38, 39 Mental traits, human and anthro- poid agree in basic, 74 Mesethmoid bone, origin of the, 167 Microcherus, dentition of, Fig. 78, 148 Midas, top view of skull, Fig. 35, 58 Midgets, cause of, 231 Miller, G. S., on hind feet of primates, 54 Mimetic muscles, origin of the, 43, 44 Miocene, Primates began to as- sume human characters in, 64; anthropoid adaptations during, 91 Molar teeth, identity of human and anthropoid molar pat- terns, 69; fovea anterior and posterior in upper molars of anthropoids and man, 149; origin of, 90 of cynodonts, 116 of cynodonts and man com- pared, 145 of fossil man, 143 of primitive man, 76 279 INDEX Molars, lower, kinship of human and anthropoid, 146 of chimpanzee, Fig. 79, 150 of Dryopithecus cautleyi, Fig. 79, 150 of D. fontani, Fig. 79, 150 of D. fricke, Fig. 41, facing 66, Fig. 79, 150 “Dryopithecus pattern” in, 149, Fig. 80, 151 of gorilla, Fig. 79, 150 of Homo heidelbergensis, Fig. 80, 151 of orang, Fig. 79, 150 Lower (left) m., of Dryopi- thecus rhenanus, Fig. 38, 62 of Eoanthropus dawsont, Fig. 38, 62, Fig. 41, facing 66 of Homo neanderthalensis (Le Moustier), Fig. 38, 62 of Homo sapiens, Fig. 38, 62 of Leipsanolestes, Fig. 38, 62 of Parapithecus, Fig. 38, 62 of Pelycodus, Fig. 38, 62 of Propliopithecus, Fig. 38, 62 Molars, upper, of Dryopithecus rhenanus, 149 of Homo neanderthalensis (Le Moustier), Fig. 78, 148, 149 Upper (left), of Dryopithecus rhenanus, Fig. 38, 62 of Homo neanderthalensis (Le Moustier), Fig. 38, 62 of Homo sapiens, Fig. 38, 62 of Indrodon, Fig. 38, 62 of Pelycodus, Fig. 38, 62 of Propliopithecus (restored), Fig. 38, 62 Mollusca, development of eye in cephalopod, Fig. 95, 181; paired eyes of higher, 178 Mongolia, Cretaceous mammals from, 51; insectivores from Cretaceous of, Fig. 29, 50 Mongolian face, the, 170 Mongolian nose, its shape, 164, 171 Mongolians, “‘shovel-shaped”’ in- cisors of, 138 Monkeys, catarrhine, external ears of, 214; face of, frontispiece, 56, Fig. 34, facing 56; incisors of, 138; nasal chamber of, 161; nose of, 56, 57; orbital axes of, Fig. 35, 58, 196; skull of (Lasiopyga kolbi), Fig. 36, 59; platyrrhine, as offshoot from some primitive tarsioid stock, 56; face of (Cebus capucinus), Fig. 34, facing 56; lips of, 56; nose of, 56; orbital axes of Midas, Fig. 35, 58, 196 Morton, D. J., on hind feet of primates, 54 Montana, mammalian teeth from Basal Eocene of, 53; Eodelphis from Upper Cretaceous of, 47 Mouth, as dominant element of face, 4; conclusions from history of, 152; origin of, uncertain below ostracoderms, 101; nasal sac as outgrowth of, 154 of ancestral forms, 94 of Amphiorus, Fig. 54, 92, 129 of annelid worms, 6 of Cephalaspis (restoration), Fig. 57, 95 of crossopts, 130 of jellyfish (Tessera), 4, Fig. 1, 5 of Kiaeraspis (restoration), Fig. 57, 95 of lamprey, adult, 129 of lamprey, larval, 129 of man, fcetal, third week, Fig. 69, 127 of ostracoderms, 129 of Paramecium, Fig. 1, 5 of platypus, 131 of shark, Fig. 5, facing 12 Mouth-legs, of Orchestia, Fig. 2, facing 6 of trilobites, 6 Mouth pouches, embryonic, 94 of larval lamprey, longitudinal section, Fig. 56, 94 of rabbit, embryo, Fig. 56, 94 of sharks and embryo verte- brates, supported by cart- ilaginous bars, 102 Muscles of accommodation (ciliary), 193 of accommodation, in eyes of Sepia, 180 of check and lips, important to new-born mammals, 134; con- strictor, of gill arches: jaw muscles of shark derived from, 104 prevertebrate 280 INDEX Muscles—(Continued) of the ear, 133 of the ear, reduced in man, 215 of the eyeball, in man, Fig. 98, 190 of vertebrate eye, 191 of the eye of shark (Chlamy- doselachus), Fig. 6, 13, 15 Facial, origin and development of the, 43; origin of, in mam- mals, 132 of gorilla, Fig. 23, 42, 67, 124 of man, Fig. 23, 42 geniohyoglossus, of anthropoids, 126 of man, Fig. 67, 124, Fig. 68, 125 of monkey, Fig. 68, 125 of jaw development associated with change of jaw form, 116; evolution of the, Fig. 61, 103 of fishes, 104 of shark, their derivation, 104 of chimpanzee, Fig. 61, 103 of Chlamydoselachus, Fig. 8, 18, also Fig. 61, 103 of Cynognathus, Fig. 61, 103 of Didelphys, Fig. 61, 103, also 49 of Eryops, Fig. 61, 103 of man, Fig. 61, 103 of Notharctus, Fig. 61, 103 of Polypterus, Fig. 61, 103 of Scymnognathus, Fig. 61, 103 masseter, 116; at corner of mouth of some reptiles, 131; orbicularis oris, 133; orbi- cularis oris of catarrhine monkeys, 56; platysma, the origin of the, 43; pterygoid, 116-117; pterygoid, external, and mammalian joint, Fig. 22, 38, 39; sphincter colli, 43, 132 of Echidna, Fig. 23, 42 of Sphenodon, Fig. 23, 42 temporal, 116 of tongue (geniohyoglossus) in anthropoids, Fig. 67, 124 Muscle fibres, striped, function of the, 19 Mycterosaurus (Permo-Carbon- iferous), dentition of, Fig. 77, 147; skull of, Fig. 19, 33, Fig. 48, 78 281 Nares, of crossopts, 24 Naris, internal, series of skulls showing evolution of, Fig. 53, 85 of Adapis of Baphetes of Captorhinus of chimpanzee of Cynognathus of Eusthenopteron of man (Australian aboriginal) of Scymnognathus of Seymouria of Thylacinus Nasal bones, series of skulls show- ing evolution of, Fig. 49, 79; their origin in Amphibia 30; retained from fish to mammals, 86; in advanced lemuroids, 60 Nasal chamber, median partition of, 158; sinuses and antra of, 162; of mammal-like reptiles, 158; of man and monkeys, compared, 161 Nasal field, in embryonic develop- ment, 166 Nasal meati, 161; connections of sinuses with, Fig. 85, 163 Nasal pit of larval lamprey, Fig. 56, 94 Nasal sac, embryonic origin of, 154; of embryo sharks and mammals, 154 Nasal septum, rates of develop- ment of the, 167 Naso-buccal groove, of sharks, Biesen6GS a Lei Le? wloas 157 Naso-lacrymal duct, in man, Naso-pharyngeal passage, 119 Nautilus, eye of, 181 Neanderthal man, see Man, Neanderthal Negritos, the nose of, 169 Negro, the iris of, 199; develop- ment of the nose in, 167; the nose of, 169; Fig. 88, 168; the nose of, infant, Fig. 88, 168 Negro pygmy, nose of the, 164 Nematodes, effect of ultraviolet rays on, 174 Neoceratodus, 25 INDEX Nerve, seventh cranial activates sphincter colli, 43; facial, chief branches of, in man and gorilla, Fig. 24, 44; facial, of Sphenodon, Fig. 23, 42; oculomotor, of chimpanzee, 198; olfactory, course and function of, 155; optic, de- scription of, 187, 188; optic, human, function of, 191; optic, of Sepia, 180; of semicircular canals, 204, 206 Nerve cells, olfactory, 157 Nervous system of primates, studies of, 63 New Mexico, Notharctidze from Eocene of, 54; early placental mammals from, 52 Nictitating membrane, of, in man, 194 Norway, ostracoderms of, 10 Nose, progressive stages in devel- opment of, vertebrate, 157; shapes of the human, 164, Fig. 89, facing 170; great diversity of form in the, 172; extreme forms of, Fig. 89, facing 170; factors controlling form of the, 168-171; effect of the bony palate on, 169; effect of premaxille on, 168; hereditary factors in 172, 236; development of human, 162; development in fetal and adult man, 163; varying rates of development of its parts, 167; Prof. Schultz’ studies on growth of, 172; embryonic stages of human, Fig. 65, 120, Fig. 82, 159; human, as index of character, 220; shows kin- ship of man and anthropoids, 163; nasal sinuses of man and anthropoids, 161; septal car- tilage of human, Fig. 88, 168; origin of median cartilage in mammalian, 167; olfactory capsules of mammal-like rep- tiles, 158; naso-buccal groove of shark, Fig. 66, 121, 154, 157; nasal meati, 161; nasal vestiges sac, embryonic origin in shark and mammal, 154; embryonic development of mammalian, 166; Jacobson’s organ, 158; lateral (or alar) cartilage, 167; primary func- tion of the, 154; essential parts of the, 155; bridge of the, 170; the humped x., cause of, 169; the Mongolian nose, 171; the pug_ nose, cause of, 169, 171; the wide nose, cause of, 169; shape of, in achondroplasia, 169, 230 in acromegaly, 171 in cretinism, 171 of gorilla, 170 of gorilla, foetal, Fig. 84, 161 of catarrhine monkey, 56 of shark, 154 of man, feetal, Fig. 84, 161 of man, infant, 167 of Armenian, Fig. 89, facing 170 of Australian aboriginal, 169 of South African Bushman, Fig. 89, facing 170 of Hittite type, 169; Fig. 89, fac- ing 170 of Melanesian, 169 of Mongolian, 164 of negrito, 169 of negro, 169, Fig. 88, 168 of negro child, Fig. 88, 168 of Papuan, 169 of African pygmy, 164, Fig. 89, facing 170 of Rhodesian man, 72 of Tasmanian, 169 of Tyrolese, Fig. 89, facing 170 of white adult, Fig. 88, 168 of white child, Fig. 88, 168 Nostrils of catarrhine monkeys, 57 Nostrils, internal (choanz) of early amphibia, Fig. 53, 85, 118 of lung fishes, 157 Notharctide, from Eocene of Wyoming and New Mexico, 54; compared with lemurs of Madagascar, 54 Notharctus (Eocene), compared with chimpanzee and man, 65; position of eyes in, Fig. 35, 58, 196; jaw muscles of, Fig. 61, 103; olfactory cham- ber of, 196; skeleton of N. osborni, Fig. 32 facing 54; 282 IN DEX Notharctus (Eocene)—(Continued) skull of, side view, Fig. 33, 55, Fig. 36, 59, Fig. 48, 78; skull of, top view, Fig. 35, 58 Notochord, 21 Nycticebus, external ear of, Fig. 110, 213 Ocellus of flatworm (Planaria), Fig. 2, facing 6 of jellyfish (Catablema), Fig. 91, 175 of jellyfish (Sarsia), Fig. 91, 175 of sand flea (Orchestia), Fig. 2, facing 6 Octopus, eyes of, 179 Oculomotor nerves, of chimpan- zee, 198 Olfactory capsule, its place in the skull structure, 83; in em- bryonic development, 167; the value of double, 156; in human embryo, 162, Fig. 65, 120 of mammal-like reptiles, 158 of shark, Fig. 6, 13, 14, Fig. 7, 17, 122, 154, Fig. 81, 155 Olfactory chamber of early amphibia, 118 of Lemur, 58 of Notharctus, 196 of Notharctus osborni, 56 Olfactory membrane, function of the, 158 Olfactory nerve, course and func- tion of the, 155 Olfactory nerve cells, as special- ized cell of skin, 157 Olfactory pit, in human embryo, Fig. 65, 120 of shark, 122 Olfactory sac, 157 Olfactory sense organs, 155 Oligocene, lower, separation of man from early anthropoids in (Osborn), 74 Ontogenetic study of physiog- nomy, 224 Opercular notch, eardrum formed in location of, 89 Opercular tract, elimination of plates of, in early amphibia, Fig. 17, 30, 114 Opossum, fossil (Eodelphis), 47; skull of, Fig. 48, 78; compared to that of Didelphys, Fig. 27, 48 Opossum, recent (Didelphys), most primitive marsupial of today, 47; with young, Fig. 26, facing 46; jaw muscles of, Fig. 61, 103; skull compared with that of Kodelphis, Fig. 27, 48; skull of, Fig. 28, 49 Optic capsule, of shark, Fig. 7, 17 Optic cups, formation of the, Fig. 97, 185, 187; development of retina from, in vertebrates, 181 Optic nerve, description of the, 188; function of the, 191; of Sepia, 180 Optic pouch, of the jellyfish, 175 Oral cartilage, of shark and embryo vertebrates, 102 Orang, pattern of papille vallate similar to that in man, 123; external ear of, Fig. 110, 213, 214; palatal arch of female, Fig. 74, 140; lacrymal bone of, 200; nose of, 169; skull of young, front view, Fig. 102, 197; teeth, lower molar, Fig. 79, 150; tongue of, 123 “Orang type,” of human ear, Fig. 110, 213 Orbicularis oris muscle of anthropoid apes and man, 133 of catarrhine monkeys, 56 Orbital axes of lemuroids, Fig. 35, 58, 196 of platyrrhine monkeys, Fig. 35, 58, 196 of catarrhine monkeys, Fig. 35, 58, 196 of anthropoids, Fig. 35, 58, 196 Orbits of advanced lemuroids, 60 of lower primates, 60 of orang, 169 of Tarsius, Fig. 31, facing 53, 60 Orchestia (Sand-flea), Fig. 2, fac- ing 6 Organ of Corti, Fig. 103, 203, 204 Organs, lateral line, of fishes, 206 Organ, parapineal, 186; pineal, 186 Ornithorhynchus, mouth of, 131 _ the, 283 INDEX Oronasal groove, see nasobuccal groove Osborn, H. F., evidence for his conclusions on ancestry of placental mammals, 51; view of separation of man and apes from primitive stock, 74 Ossicles, auditory, see Ear, audi- tory ossicles Osteolepide (Crossopterygii) closely related to Amphibia of Carboniferous, 114 Osteolepis (Devonian), skull of, cross section, Fig. 9, facing 20; seen from above, Fig. 11, fac- ing 22; spiracular cleft in, 209 Ostracoderms, probably ancestral to cyclostomes, 186; a modern descendant of the, Fig. 59, 97; their use of cilia for ingestion, 95; ingestion transitional be- tween ciliary and predacious, 97; origin of mouth jaws and teeth uncertain below, 101; mouth of, 129; denticles in skin of, 117; teeth of (Lanarkia), 117; Prof. Patten on, 8; Stensié on cephalaspid o., 94; Anaspida, characters of the order, 96; Fig. 4, 11 Cephalaspis, restoration of, Fig. 4, 11; restoration of head of, Fig. 57, 95 Kieraspis, restoration of head of, Fig. 57, 95 Lanarkia, shagreen denticles of, 100 Pteraspis, restoration of, Fig. 4, 11 Pterolepis nitidus, restoration of, Fig. 4, 11, also Fig. 58, 96 Otic capsule, as a component of the chondrocranium, 83; of shark, Fig. 7, 17, Fig. 81, 155 Otic notch, in early amphibians, 29, 209, Fig. 17, 30 of Seymouria, 32, Fig. 19, 33 in reptiles, 209 Otoliths, 206 Paleogyrinus, skull of, showing loss of opercular series, Fig. 17, 30; side view of, Figs. 48-52, 78-82 Palatal arches, reduction in size of teeth, factor in shortening of, 143 of gibbon, female, Fig. 74, 140 of gorilla, male, Fig. 74, 140 of chimpanzee, female, Fig. 74, 140 of orang, female, Fig. 74, 140 of Neanderthal man (Le Mous- tier), Fig. 74, 140 of modern white man, Fig. 74, 140 Palatal bone, 83 Palatal region of cynodonts, Fig. 52, 82 of Seymnognathus, Fig. 53, 85, 118 progressive changes in, Fig. 53, 85, 118 of mammals, Fig. 53, 85, 119 in human embryo, 120 Palate, bony, its effect on shape of nose, 169; comparative anatomy of human, Fig. 66, 121; cleft, human, 228; cleft palate, in Felis leo, Fig. 66, 121; fleshy, possible rudi- ments in Scymnognathus, 119; of lizard, Fig. 66, 121; primitive, formation of, 122; reptilian, 122; secondary, in human embryo, Fig. 66, 162; of cynodonts, Fig. 52, 119; soft, of mammals, 119 Palatine bone, of cynodonts, 119 Palatoquadrate, of Devonian crossopts, 109 of Diadectes, Fig. 62, 105 of shark, Fig. 6, 13, 17, Fig. 7, 17, Fig. 8, 18, 106 Palatoquadrate cartilages, 102 Paleocene of New Mexico, early placental mammals in, 52 Pantotherian, dentition of, Fig. 77, 147 Papille vallate, of orang similar to those of man, 123 Papuans, noses of, 169 Paramecium (Slipper animalcule), face of, 4; mouth of, Fig. 1, 5 Parapineal eye, Fig. 97, 185; as directional organ, 200 Parapineal organ, origin of, 187; in pre-chordates, 186 Parapithecus, lower jaw of P. fraasi, Fig. 37, 61; left lower molar of, Fig. 38, 62 284 INDEX Parasphenoid, of fish, 22; enlarge- ment in amphibians of, 31 Parietal bones, evolution of, Fig. 49, 79; of opossum, 49; as components of dermocranium, 83; among dominant elements of human skull, 87 Parker, G. H., cited on hearing of fishes, 206 Parker, W. K., cited on embry- ology of sturgeon, 209 Patten, William, theory of deriva- tion of vertebrates, 7, 8, 92, 182; cited on derivation of vertebrate eye, 182 Pecten, eyes of, 178 Pelvic floor, Sir Arthur Keith on the primate, 63 Pelvis, evolution of primate, 63 Pelycodus, lower jaw of, Fig. 37, 61; left lower and upper molars of, Fig. 38, 62 Pen-tailed tree-shrew, Fig. 30, facing 52 Perameles, formation of meniscus in embryo of, Fig. 22, 38, 39 Periotic mass, fusion of squamosal bone with, in mammals, 88 Permian period, labyrinthodonts and stegocephalians of the, 115; Mycterosaurus, of the, 34; Seymouria, of the, 32 Permocynodon, middle ear of, Fig. 11g. S17 Pharynx, function in respiration of, 162 of Amphiorus, 98 of larval lamprey, 98 Philtrum, of the lip, in man, 133; embryonic development of the, 166 Phototropism, 174 Physiognomy, anthropological method of study of, 224; Aristotle on, 220; the author analyzes his own face, 225- 229; clinical method of study of, 224; Darwin’s study of, 223; Duchenne’s study of (experimental method), 223; embryological study of, 224; evolutionary method of study of, 223; experimental method of study of (Duchenne’s), 223; genetic method of study of, 224; origins of modern science of, 222; physiological method of study of, 224; psychiatrist’s method of study Ole 2255 psychoanalyst’s method of study of, 225; psychologic method of study of, 224; Sir Charles Bell’s study of, 222; study of cor- relation between crime and types of, 225 Piltdown man _ (Koanthropus), canine tooth of, 141; char- acters of, 72, 73; lower jaw of, Fig. 37, 61; Fig. 45, 71, 143; lower molar of, Fig. 38, 62; Fig. 41, facing 66 Pineal eye, Fig. 97, 185, 200 Pineal organ, origin of, 187; in pre-chordates, 186 Pithecanthropus (Trinil man), characters of, 72, 73; skull of (side view), Fig. 42, 68; skull of (top view), Fig. 43, 69 Pituitary glands, effects of diseased, 171 Placental mammals, their fore- runners from Mongolia, 51; in Basal Eocene and Pale- ocene of New Mexico, 52 Planaria, eyes of, as directional organs, Fig. 93, 178; head and tail differentiation of, Fig. 2, facing 6; location of eyes of, Fig. 92, 177 Plant life, origin in Archeozoic era, 27 Plate, L., cited on origin and development of the eye, 174- 188; summary of literature on eyes of invertebrates and vertebrates, 174; on eyes of Amphioxus, 183, 184; on eye capsules of flatworm, Fig. 93, 178; on human vision, foot- note, 174; on paired eyes of vertebrates, 178 Platypus, believed related to some mammals of Age of Reptiles, 47; mouth of, 131 Platyrrhine monkeys, see Monkeys, platyrrhine Platysma muscle, origin of, 43 Pleistocene, lower, already several types of man in, 73 285 INDEX Plica semilunaris, of human eye, Fig. 101, 194; as vestige of third eyelid, 194 Pliocene, fossil human record a blank during the, 70, 142; reduction of human canine teeth may have occurred dur- ing the, 142 Polyplocodus, teeth of, Fig. 18, following, 30 Polypterus, embryo of, Fig. 14, 26; jaw muscles of, Fig. 61, 103; representative of lobe-finned ganoids, 24 Postfrontal bone, eliminated by time of earliest mammals, 88, 90 Postorbital bone, joint process of frontal and malar replace, 90; eliminated by time of earliest mammals, 88, 90; evolution of, Fig. 51, 81 Postsplenial bone, series of skulls showing evolution of, Fig. 52, 82; reduction of, 88; of Megalichthys, Fig. 64, 111; of Trimerorhachis, Fig. 64, 111 Posture, its effect upon develop- ment of face, Fig. 36, 59, 64, 66; characters of early primates adapted to, 67, Prearticular bone, of Trimeror- hachis, Fig. 64, 111 Pre-chordates, eyes of, 186 Predaceous habits, organization of primitive vertebrates adapted to, 101 Prefrontal bone, evolution of, Fig. 51, 81; eliminated by time of earliest mammals, 88 Premaxilla, evolution of, Fig. 50, 80; Fig. 53, 85; position of, 107; effect on shape of nose, 168; unites with maxilla in anthropoids and man, 87; of crossopt and early amphibian are homologous, 107; of Baphetes, Fig. 63, 108; of Eusthenopteron, Fig. 63, 108; covered with skin in early amphibians and reptiles, 130; origin of, in crgssopts, 130 Premolars, in primitive man, 76; origin of, 90; of cynodonts, 116; of fossil man, 143; of Dryopithecus, _Sivapithecus, Neanderthal and Homo sapiens, Fig. 75, 144; front lower, of anthropoids, 144; nearest affinities of human, 144 Preoperculum, elimination of, Fig. 17, 30, 114 Presphenoid bone, 167 Pre-vertebrates, see Chordates Prevomer bones, evolution of, Fig. 53, 85; of Devonian crossopts, 100 Primates, mammals of Basal Eocene of Montana approach the, 53; family Notharctide, 54; hind foot of, always of tree-grasping type, 54; com- parison of hands and feet of fossil and recent, 54; arboreal stage passed through by all, 54; skeleton of primitive fossil, Fig. 32, facing 54; skull of primitive fossil, Fig. 33, 55; faces of lower, Fig. 34, facing 56; traces of insectivorous dentition in, 57; ears of the lower, 57; top view of skulls of, Fig. 35, 58; side view of skulls of, Fig. 36, 59; Epitome of Fossil History of, Figs. 37, 38, 61, 62; value of study of fossil and recent, 60; rare as fossils, 60; relation of upper jaws to eyes in, 60; Keith cited on diaphragm, abdomen and pelvic floor of, 63; pro- gressive series presented by brains of, 63; agreement of results of studies on internal and external anatomy and fossil history of, 63; time of assumption of human char- acters of, 64; enlargement of brain characteristic of, 64; correlated use of eyes, hands and feet in, 64; man derived from Old World, 65; develop- ment of eyes of, 65; char- acters adapted to diet and posture in, 67; characters of man, and 67; man owes 286 INDEX Primates— (Continued) development of eyes to early, 90; postorbital bar replaced by process from frontal and malar bones in earliest, 90; character of tongue in, 123; branchial skeleton of, homo- logous with human, 128; salivary glands of, 129; lips of, 133; Jacobson’s organ lacking or vestigial in higher, 159; nasal septum of, 167; eyes of primitive, 196; re- duced olfactory apparatus in higher, 196 “Primitive streak,’ mouth of Tessera represents, 5 Pro-anthropoids, man _ derived from, 69; changes of skull in arboreal, 91 Protista, supposed rudimentary eyes of, 174 Protozoa, among earliest marine invertebrates, 8 Psychiatrist, method of study of physiognomy by, 225 Psychoanalyst, method of study of physiognomy by, 225 Psychologic method of study of physiognomy, 224 Pteraspis, Fig. 4, 11; mouth of, 96 Pterolepis nitidus, Fig. 58, 96 Pterygoid bone, of Diadectes, Fig. 62, 105; effect of increase in size of, 117 Pterygoid muscle, origin of men- iscus in, Fig. 22, 38; Gaupp cited on, 39; influence of its development on skull, 117 Pulp cavity, in formation of teeth, 134, Fig. 71, 135 Purple, visual (rhodopsin), 189 Pygmy, African, nose of the, 164, Fig. 89, facing 170 Quadrate bone, 39; evolution of, Fig. 53, 85; of Diadectes, Fig. 62, 105 Quadratojugal bone, evolution of, Bye i o2 S23) igs) (5S) (85; reduction of, 88 Rabbit, embryo, mouth pouch of, Fig. 56, 94; labyrinth of, Fig. 104, 205 Radial symmetry, gives way to bilateral, 6 Remane, A., cited on incisors of chimpanzee, 138, 141; study of anthropoid teeth by, 142; cited on front lower pre- molar of man and anthro- poids, 145 Reptiles, Seymouria most primi- tive, 32; sphincter colli of, 43; period of dominance of, 45, Fig. 25, 46; loss of inter- and supra-temporals from skull of early, 89; progressive changes in teeth of, Fig. 53, 85, 115; naso-buccal channel of, 122; skin-covered maxille, premaxillze and dentary of early, 130; muscle at corner of mouth of some recent, 131; Jacobson’s organ in, 158; stage in development of nose of human embryo like that of, 162; tympanum of, 217; mam- mal-like, skulls of earlier and later, Fig. 20, 35; progressive upgrowth of dentary bone of, Fig. 21, 37, 108; initial stages in formation of hair possibly developed in Triassic, 42; opossum similar to Triassic, 48, Fig. 28, 49; superior maxillary of, Fig. 50, 80, 87; inferior maxillary in, 87; origin of temporal fossa and zygomatic arch in early, 89; development of temporal fossa in later, 90; palatal region of, Fig. 53, 85, 118; nasal septum of, 167; relation of parts of middle ear in, Fig. 112, 217; internal ear of advanced, 218; angular bone of, 218 Reptilian postorbital bar, loss of, by early mammals, 90 Reptilian stage, in development of auditory ossicles, Fig. 115,221 Respiration, origin and function of the diaphragm, 41; of early amphibians, 118; of mammals, 119; of sharks, Keith cited on, 122; of dipnoan fishes, Keith cited on, 122; of air-breathing fishes and amphibia, 157 287 INDEX Retina, of the squid (Sepia), 180; of cephalopods, 181, Fig. 95, 181; of vertebrates, developed from optic cup, 181; forma- tion of the, Fig. 97, 185; of dorsal eyes in pre-chordates, Studnicka cited on, 186, 187; apparently represents in- verted patch of epithelium, 187; layers of the, 188; likened to sensitive plate of camera, 189; function of human, 191; of shark, Fig. 99, 192; human, Fig. 100, 193 Rhinarium, of lemur, 56 Rhizodopsis, skull of, Fig. 17, 30; Figs. 48-52, 78-82 Rhodesian man, skull of, Fig. 42, 68, 72 Rhodopsin (visual purple), 189 Ribs, their origin, 21 “Rods,” of the primitive eye, 175; in eyes of cephalopods, Fig. 94, 179, 180; in eyes of vertebrates, 180; in organ of Corti, 204 Rods and cones, as layer of retina, 188; of human eye, 190 Rotifers, effect of ultraviolet rays on, 174 Ruge, G., on origin of facial muscles, 44; researches of, show anatomy of facial muscles most like in man and anthropoids, 132, 133; mono- graph on facial musculature of, shows likeness between ear muscles of chimpanzee and human embryos and children, 215 Sacculus, of inner ear of lower vertebrates, Fig. 104, 205-206 St. Bernard dog, acromegaly and gigantism in, 231 Salamander, skull of fcetal, Fig. 62, 105; embryo of, Fig. 14, 26 Salivary glands, of man and apes, 129 Sand-flea (Orchestia), Fig. 2, fac- ing, 6 Sarsia, eye of, Fig. 91, 175 Scales, origin of, in skin of pre- vertebrates, 101; of crossopts, same nature as covering of primary jaws, 106 Scallop (Pecten), eyes of, 178 Schultz, A. H., cited on hind feet of primates, 54; on nose of human feetus, 164; on devel- opment of human nose, 167; studies on human nose, 172 Sclera, of shark, Fig. 99, 192; of human eye, Fig. 100, 193 Sclerotic layer, of eye of verte- brates, 188 Scylacosaurus, dentition of, Fig. 77, 147 Scymnognathus, skull of, Fig. 20, 35; Fig. 21, 37; Figs. 48-53, 78-85; jaw muscles of, Fig. 61, 103 Sea-cucumber, larva of (Auri- cularia), Fig. 55, 93 Sebaceous glands, origin and function of, 41 Semicircular canals, of ear of shark, 16; of human ear, 202, Fig. 103, 203; of primi- tive fish, 204; nerves of the, 204, 206; of frog, Fig. 106, 208 Sense organs, origin from skin of, 101; mystery of their origin, 156; value of bilateral ar- rangement of, 156 Sepia (squid), structure of eyes of, Fig. 94, 179, 180 Septal cartilage, in man, Fig. 88, 168 Septum, nasal, origin of, 167; rates of development of, in anthropoid and man, 167 Seymouria, restoration of face of, frontispiece; most primitive reptile, 32; otic notch of, 32; skull of, Fig. 19, 33; Figs. 48-53, 78-85; teeth of, 118 Shagreen, of skin, origin of teeth, 19; in primitive sharks, 109 Shagreen denticles, development of, into teeth, Fig. 60, 99; skin of pre-vertebrates gave rise to, 101 Shark, Devonian (Cladoselache), restoration of face of, frontis- piece; our own face shown in that of, 12; recent (Chlamy- doselachus), face of, Fig. 5, 288 INDEX Shark, Devonian—(Continued) facing 12; instruments of pre- cision in head of, Fig. 6, 13, 14; olfactory capsules of, Fig. 6, 13, 14; Fig. 7, 17, Fig. 81, 155; eye muscles of, Fig. 6, 13, 15; shark nearer to man than to invertebrates, 14, 102; and his prey, 15; taste organs of, 16; ““ampulle”’ in head of, 16, 204; ‘“‘internal ears” of, 16; cartilaginous skeleton of head of, Fig. 7, 17; primary jaws of, Figs. 7, 8, 17, 18, Fig. 62, 105; palatoquadrate of, Figs. 7, 8, 17, 18; labial cartilages of, Figs. 7, 8, 17, 18; hyoid of, Fig. 7, 17; hyomandibula of, irs 7s Sia el Os ay a; muscles of, Fig. 8, 18, Fig. 61, 103; derivation of jaw muscles of, 104; otic capsule of, Fig. 7, 17, Fig. 81, 155; optic capsule of, Fig. 7, 17; skin of the, 19; chemical composition of skeleton of, 23; facial expression of, 19; mouth pouches of embryonic, 94; three stages in develop- ment of teeth of, Fig. 60, 99; visceral arches in predecessors of, 104; mouth pouches sup- ported by cartilaginous bars, 104; secondary jaws repre- sented only by skin, 106; development of teeth in typ- ical, 109; less advanced than crossopt, 113; tongue of, 123; dissection of head of, Fig. 81, 155; oronasal groove of, Fig. 66, 121, 154, 157; method of respiration of, 122; mouth of, 130; spiracle of, Fig. 81, 155; eye of, nearer to that of man than to any invertebrate eye, 191; horizontal section of eye of, Fig. 99, 192; laby- rinth of, Fig. 104, 205 Shark-like stage, of human eye, 191 Shoulder-girdle, Watson cited on, of fossil amphibians, 28, Fig. 15, 28 Shrew, see Tree-shrew Shylock, and the shark, 12 Silurian and Devonian ostraco- derms, 10, Fig. 4, 11; Kier and Stensié cited on, 10, 11, 12, 94, 97, 98; Lanarkia, 100 “Simian shelf” of Piltdown man, Fig. 45, 71, 143 Sinus, nasal, of man and anthro- poids, 161, 162; frontal, con- nection with nasal meati, Fig. 85, 163; ethmoid, con- nection with nasal meati, Fig. 85, 163; sphenoid, con- nection with nasal meati, Fig. 85, 163 Sivapithecus, traces of derivation of human dentition from, 58; lower jaw of, Fig. 37, 61; dental formula of, Fig. 37, 61; front lower premolars of, 144, Fig. 75, 144; upper molars of, 140 Skeleton, of shark, its chemical composition, 23; of Noth- arctus, Fig. 32, facing 54 Skin, of shark, 19; potentialities of, 100; structures derivative from, 101; origin of some sense organs in, 101; origin of teeth in, 101, 109; dentary, maxille and premaxille of advanced crossopts covered by, 130; on bill of Platypus, 131 Skull, heritage of the, 20, 28, 89; structure of the, 21, 83; comparison of lobe-finned ganoid, with early amphibian, 29, 107; simplification of the, 31; formation of mammalian joint of, 39, 90; of some placental mammals ap- proaches that of lowest Pri- mates, 53; dominant elements of human, 87; evolution of human, from fish to man, Figs. 48-53, 78-85; changes in lateral view of, from fish to man, 86-91; factors deter- mining changes in structure of, 88-89; genesis of temporal bone of, 88; loss of bones cov- ering branchial chamber of, 89; changes of, in arboreal pro-anthropoids, 91; attach- 289 INDEX Skull— (Continued) ment of primary upper jaw to, 104, Fig. 62, 105; dentary- squamosal contact in, 108, 109; Keith cited on develop- ment of, 122; position of temporal region of, condi- tioned by size of brain, 170; of achondroplastic dwarf, 230 of Adapis, Fig. 53, 85 of Arctocebus, top view, Fig. 35, 58 of Australopithecus, Fig. 42, 68, 72; side view, Fig. 46, facing 72 of Baphetes, under side, Fig. 53, 85, Fig. 63, 108 of chimpanzee, top view, Fig. 35, 58, Fig. 43, 69 side view, Fig. 36, 59 near to human, 65 front view, Fig. 44, 70 bones of, Figs. 48-53, 78-85 longitudinal section, Fig. 83, 160 young, front view, Fig. 102, 197 of Cro-Magnon, side view, Fig. 42, 68; top view, Fig. 43, 69; high-bred, 73 of Cynognathus, Fig. 53, 85 of Deltatheridium, Fig. 29, 50 of Diadectes, Fig. 62, 105 of Eodelphis, Fig. 27, 48, Fig. 48, 78 of Eusthenopteron, Fig. 53, 85, Fig. 63, 108 of gorilla, young, Fig. 102, 197 of Hylobates (gibbon), Fig. 35, 58 of Ictidopsis, Fig. 20, 35, Fig. 21, 37, Fig. 28, 49, Figs. 48-52, 78-82 of Lasiopyga, side view, Fig. 36, 59 of Loxomma allmani, Fig. 16, facing 28 of man, Australian aboriginal, Fig. 58, 85; bones of, Figs. 48-52, 78-82; side view, Fig. 36, 59; longitudinal section, Fig. 83, 160; infant, front view, Fig. 102, 197; Modern European, Fig, 44, 70 290 of Midas (marmoset), Fig. 35, 58 of Mycterosaurus, Fig. 19, 33; bones of, Figs. 48-52, 78-85 of Neanderthal (Chapelle aux Saints), side view, Fig. 42, 68; top view, Fig. 43, 69; front view, Fig. 44, 70 of Notharctus osborni, side view, Fig, 33, 55, Fig. 36, 59; top view, Fig. 35, 58; bones of, Figs. 48-52, 78-82 of opossum, recent, Fig. 27, 48, Figs. 49-52, 79-82 of orang, young, Fig. 102, 197 of Osteolepis, cross-section, Fig. 9, facing 20; top view, Fig. 11, facing 22 of Palwogyrinus, Fig. 17, 30; bones of, Figs. 48-52, 78-82 of Piltdown, Fig. 42, 68, 141 of Pithecanthropus, side view, Fig. 42, 68; top view, Fig. 43, 69; ape-like features of, 72 of Primates, showing progres- sive shortening of the muzzle, Fig. 36, 59 of Rhizodopsis, Fig. 17, 30; bones of, Figs. 48-52, 78-82 of Rhodesian man, Fig. 42, 68; gorilla-like details of nose, 72 of salamander (fetal), Fig. 62, 105 of Scymnognathus, Fig. 20, 35; posterior view, Fig. 21, 37; bones of, Figs. 48-53, 78-85 of Seymouria, Fig. 19, 33; bones of, Figs. 48-53, 78-85 of Talgai man, Fig. 42, 68; proto-Australoid type of, 72; muzzle of, 143 of Tarsius spectrum, Fig. 35, 58 of Thylacinus, posterior view, Fig. 21, 37; under side of, Fig. 53, 85 of Zalambdalestes lechei, Fig. 29, 50 Slipper animalcule, mouth of, 4, Fig. 1, 5 Smelling organs, of shark, 14, 15, 17, Fig. 81, 155, 154-156 Smell, sense of, not dominant in anthropoid apes, 65; sight developed at expense of, by pro-anthropoids, 91 INDEX Smith, G. Elliot, cited on evolution of primate brain, 63 Sonntag, Charles F., facial muscles, 132 Spaniel, King Charles, ateleosis in, 231 Spectral tarsier (Tarsius), Fig. 31, facing 53 Spinal cord, of Amphiorus (sec- tion), Fig. 96, 183 Sphenoid bone, 83; sinus of the, 162; effect on the face of the, 170 Sphenoid sinus, connection with nasal meati, Fig. 85, 163 Sphenodon, head of, Fig. 23, 42 Sphenodon, see also Hatteria Sphincter colli, as origin of facial muscles, 43, 44; of Echidna, Fig. 23, 42; of Sphenodon, Fig. 23, 42; migration of, 132 Splenial bone, evolution of, Fig. 52, 82; reduction of, 88; of Megalichthys, Fig. 64, 111; of Trimerorhachis, Fig. 64, 111 Spiracle, of shark, Fig. 6, 13, Fig. 81, 155 Squamosal bone, meniscus _be- tween dentary and, in embryo Perameles, Fig. 22, 38; socket of lower jaw in the, 39; evolution of, Fig. 52, 82; contact with ascending ramus of dentary in mammals, 87, 108, 109; fused with periodic mass in mammals, 88; only remnant of temporo-mandi- bular series in mammals, 88 Squid, eye of, Fig. 94, 179; comparison of eyes of, with those of vertebrates, 179, 180 Stapes, of human ear, Fig. 103, 203, Fig. 111, 216; derivation of the, 215; of frog, Fig. 106, 208; of Permocynodon, Fig. 112, 217; of foetal armadillo, Fig. 114, 221; of human embryo, Fig. 115, 221 Starfish (Bipinnaria), larva of, Fig. 55, 93 Stegocephalians, teeth of the, 115 Stensio, Erik A.: Son, cited on ostracoderms, 10-12, 94, 97, 98; on cyclostomes, 97, 98 work on Stereoscopic vision, of anthropoid apes, 65; of human eye, 189 Stockard, Charles R., studies on growth, 172, 231, 238; on abnormal human and animal types, 230; classification of human faces, 232; description of linear and lateral types, 233-236; Fig. 117, 232; Fig. 118, 234; on crossing of linear and lateral types, 237 Studnigéka, F. K., evolution of vertebrate eye figured by, Fig. 97, 185; cited on embry- ology of eye in lampreys, 186 Sturgeon, embryo, hyoid gill clefts in, 209, Fig. 107, 209 Suboperculum, elimination of, Fig. 17, 30, 114 Sudoriparous glands, origin and function of, 41 Supraoccipital, membranous part of the, 83 Supratemporal bone, evolution of, Fig. 49, 79; reduction of, 88; loss of, by reptiles, 89 Surangular bone, evolution of, Fig. 52, 82; reduction of, 88: of Megalichthys, Figs. 64, 111; of Trimerorhachis, Fig. 64, 111; of turtle embryo, Fig. 64, 111 Sweat glands (sudoriparous), origin and function of, 41 Swede, Nordic, face of, Fig. 90, facing 172 Sylvan life, assisted divergent evolution of primates, 57 Symmetry, radial, gives way to bilateral, 6 Tabular bones, evolution of, Fig. 49, 79; disappearance in mammals of, 86 Talgai man, skull of, Fig. 42, 68, 72; muzzle of, 143 Tarsioid stock, platyrrhine monk- eys as offshoot from some primitive, 56 Tarsius (the Spectral Tarsier), Fig. 31, facing 53; mammalian teeth from Basal Eocene of Montana related to, 53; top view of skull of, Fig. 35, 58; eyes and orbits of, 60, 196 291 INDEX Tasmanian aborigines, face of, frontispiece; noses of, 169 Taste organs, of sharks, 16 Tatusia, fcetal auditory ossicles in, Fig. 114, 221 Tear ducts, Fig. 101, 194; glands, 194 Teeth, evolution of mammalian teeth made possible by change in articulation of jaw, 39; anthropoid food and, 57; human diet and, 57; traces of derivation from primitive an- thropoid stage of human, 58; diagrammatic history of primate, Fig. 37, 61; evolu- tion of primate, 63; identity of human and anthropoid molar patterns, 69; changes in teeth of primitive man, 76; pro-mammalian reduction of successional teeth to two sets, 90; true teeth lacking in predecessors of vertebrates, 97; of higher vertebrates, origin in shagreen denticles, 100; origin of, uncertain below ostracoderm _ grade, 101i; of herbivores, not an- cestral to carnivorous types, 101; labyrinthodont pattern of, Fig. 18, following 30, 112; gradual elimination of, in upper primary jaw, Fig. 53, 85, 115; summary of early history of, 117; embryonic development of, 134; three stages in development of human, Fig. 71, 135; alleged “triconodont” stage in hu- man, 136; differences between human and anthropoid, 141; reduction of front teeth in man foreshadowed in fetal stages, 143; reduction of, factor in shortening palatal arch, 143; effect of civilization on human, 149; numbers of, in man and anthropoids, 145; comparison with those of Dryopithecus and Sivapithe- cus, 149; nose form and, Fig. 89, facing 170, 169; incisors, human, 136; three types of upper central, 138, Fig. 73, 292 139; canines, dog-toothed type of predatory animals, 115; souvenirs of carnivorous ancestry, Fig. 50, 80, 136; ““feminized”’ aspect of hu- man, 141; diminution of human lower, 144; in func- tional alignment with incisors in man, 144; premolars, front lower, of anthropoids, 144; human, history of, 146; molars, of anthropoids, 57; comparison of human and cynodont, 145; kinship of human and anthropoid, 146; human, history of, 146; fovea anterior of, in anthropoids and primitive man, 149; fovea posterior of, in anthropoids and primitive man, 149; lower, 149; “cruciform pat- tern” of, Fig. 80, 151; “Dry- opithecus pattern” of lower, 149, Fig. 79, 150 of amphibians, 31 of Australian aboriginal, Fig. 80, 151 of chimpanzee, Fig. 74, 140; Fig. 79, 150 of crossopts, on dentary, 108; origin of, 109; structure of fossil, Fig. 18, following 30, 112; attachment to derm bones, 112; advance toward higher vertebrates of, 113; origin of larger teeth of, 117 of cyclostomes, 98, Fig. 60, 99 of cynodonts, Fig. 53, 85, 115; mammal-like dentition, 116 of Cynognathus, Fig. 77, 147 of Deltatheridium, Fig. 77, 147 of Diademodon, Fig. 77, 147 of Didelphodus, Fig. 77, 147 of Dryopithecus, rhenanus, Fig. 38, 62; fontani, Fig. 75, 144, Fig. 79, 150; cautleyi, Fig. 75, 144, Fig. 79, 150; fricke, Fig. 41, facing 66; Fig. 79, 150 of Ehringsdorf man, see Man, Neanderthal of Egyptian, Fig. 72, 137 of Eoanthropus, Fig. 37, 61, Fig. 38, 62, Fig. 41, facing 66, 72, INDEX Teeth— (Continued) 141, 143; see also Piltdown man of ganoids, 23, Fig. 18, following 30 of gorilla, Fig. 72, 137, Fig. 74, 140, Fig. 79, 150; of gorilla child, Fig. 76, 146 of Heidelberg man, 143, Fig. 37, 61, Fig. 80, 151 of Hindu, modern, Fig. 80, 151 of Homo _ heidelbergensis, see Heidelberg man of Homo neanderthalensis, see Neanderthal man of Homo sapiens, Fig. 37, 61, Fig. 38, 62, Fig. 72, 137, Fig. 74, 140, Fig. 75, 144, Fig. 76, 146, Fig. 78, 148, Fig. 80, 151 of Indrodon, Fig. 38, 62 of lamprey, 98, Fig. 60, 99 of Leipsanolestes, Fig. 38, 62 of Lozxomma allmani, Fig. 18, following 30 of Michrochoerus, Fig. 78, 148 of Mycterosaurus, Fig. 77, 147 of Neanderthal man (Ehrings- dorf), Fig. 72, 137, Fig. 75, 144, Fig. 80, 151 of Neanderthal man (Le Mous- tier), Fig. 38, 62, Fig. 72, 137, Fig. 74, 140, Fig. 78, 148, Fig. 80, 151 of orang, Fig. 79, 150 of pantotherian (pro-placental,) Fig. 77, 147 of Parapithecus, Fig. 37, 61 of Pelycodus, Fig. 37, 61 of Piltdown man, 72; canine of, 141, 143; Fig. 37, 61, Fig. 38, 62, Fig. 41, facing 66; see also Eoanthropus of placental mammals, 52, 53 of Polyplocodus, Fig. 18, follow- ing 30 of Pronycticebus, Fig. 78, 148 of Propliopithecus, Fig. 37, 61 of Scylacosaurus, Fig. 77, 147 of Seymouria, 118 of shark, most primitive (Chlamydoselachus), Fig. 5, facing 12; origin of, from shagreen, 19; three stages in development of, Fig. 60, 99; nearer to those of man than to any known teeth of invertebrates, 102; develop- ment of, 100; in typical sharks, 109; not separately connected with jaws, 109; manner of replacement of, 117 of Sivapithecus, Fig. 75, 144 of reptiles, Fig. 53, 85; pro- progressive changes in, 115 of triconodont mammals, 136 Temporal bone, socket of lower jaw in, 39; squamous part of, 83; genesis of, in anthropoids and man, 88. Temporal fossa, foreshadowed in Mycterosaurus, 34; first ap- pearance of, Fig. 48, 78, 116; of Scymnognathus and Icti- dopsis, Fig. 20, 35; origin of, 89; later development of, 90 Temporal muscle, relation to development of temporal fos- sa, Fig. 48, 78, 116; evolution, of, Fig. 61, 103 Temporal region of skull, effect on the face of, 170 Fig. 37, 61; Temporo-mandibular articula- tion, 87 Temporo-mandibular series, re- duction of, Fig. 52, 82, 88 Tenrec, of Madagascar, 52. Tessera, primitive mouth of, Fig. IS Tetrapods, bony mask earliest, 28 Therapsids, Ictidopsis, skull of, Fig. 20, 35; Scymnognathus, skull of, Fig. 20, 35. Theromorph reptiles, see Reptiles, mammal-like Thylacinus (Marsupial Wolf), dentary of, Fig. 21, 37; skull of (under side) Fig. 53, 85 Thymus gland, origin in branchial arches of, 126 Thyroid gland, origin in branchial arches of, 126; effects of deficiency in, 171, 237; effect on growth of face of, 232 Tilney, Frederick, on evolution of primate brain, 63 Tongue, possible part in develop- of the 293 INDEX Tongue— (Continued) ment of secondary palate, 119; lacking in Amphiorus, 123; of hags and lampreys, 123; of shark, 123; of amphi- bians, 123; of mammals, 123; of early and higher primates, 123; papille vallate of, in orang and man, 123; figured by Klaatsch, 124; of young gorilla, Fig. 67, 124; of man, Fig. 67, 124; Fig. 68, 125; of monkey, Fig. 68, 125; muscles of, in anthropoids and man, 125; Robinson cited on, 126; influence of human, on evolution of lower jaw, 126; in human embryo, 1% Tonsils, origin in branchial arches, 126 Tooth-bearing plates, primary jaws in mammals supplanted by, 104 Tornaria, larva of Balanoglossus, Fig. 55, 93 Tragus, little known of origin of, 211; development of the, 212 Tree-shrew, pen-tailed, Fig. 30, facing 52; of Indo-Malayan region, apparent relation to Basal Eocene mammals of Montana, 53; (Cretaceous) Leipsanolestes siegfriedti, Jaw of, Fig. 37, 61; left lower molar of, Fig. 38, 62; In- drodon, left upper molar of, Fig. 38, 62 Tremataspis, Fig. 4, 11; character- istics of mouth of, 96 Triassic, Ictidopsis of, frontispiece; Fig. 28, 49; hair of mammals possibly developed during, 42; labyrinthodonts and steg- ocephalians of, 115; mam- mal-like reptiles of the, 158 Triconodont mammals, teeth of, 136 Trilobites, mouth-legs of, 6 Trimerorhachis, lower jaw of, Fig. 64, 111 Trinil man, see Pithecanthropus Turbinal bones, early structures resembling, 158; in monkeys and man, 161 Turtle, lower jaw of embryo, Fig. 64, 111 Tympanic membrane, 202; Fig. 103, 203 Tympanum, formation by amphi- bians, 89; Fig. 17, 30, 216; of human ear, 202; Fig. 103, 203; Fig. 111, 216 Tyrolese, nose of, Fig. 89, 170 Ultra-violet rays, injurious effect on many organisms, 174 Utriculus, of human ear, 202; Fig. 103, 203 Vertebral column, evolution of primate, 63 Vertebrates, derivation of, 5; Patten’s theory of derivation of, 7, 9%, 182; orthodox theory of derivation of, 7, 93; period of origin of, 8; changed heritage of, 10; antiquity of, 10; predaceous ancestry of, 12; jaws of earliest landliving, 25; real ancestors of the higher, 25; inheritance of framework of face from lower, 91; characters of ancestors of, 93; origin of mouth of, 94, Fig. 56, 94; organization of, adapted to predaceous mode of life, 101; potentialities of skin in ancestors of, 100, 101; gill pouches of embryos of higher, 102; derivation of jaw muscles of, Fig. 61, 103, 104; primary upper jaw of, at- tached to skull, 104, Fig. 62, 105; primary jaws masked by secondary, 106; secondary jaws as evidence of unity of origin of all, 107; branchial skeleton of, compared with human, 128; eyes of inverte- brate compared with eyes of, 178; origin of paired eyes of, 178; Patten’s theory of de- rivation of eyes of, 182; evidence of embryology on origin of eye of, Fig. 97, 185, 186; Eustachian tube in higher, 208 Viscera, of Primates, results of study of, 63 294 INDEX **Visceral arches,’ architecture of, 104; in predecessors of the sharks, 104 Vision, the mechanism of, 189; binocular, of Old World monkeys, anthropoids and man, 196; binocular, not possible in Notharctus, 196; developed by brachiating habit, 198 Visual cortex of brain, 191 Visual purple (rhodopsin), 189 Vitreous humor, of the eye, 188 Vomer, 83 Watson, D. M. S., studies of fossil amphibia, 28; restoration of skeleton of Eogyrinus from data of, 28; contributions to paleontology, 86 Weber, Max, evidence for con- clusions on ancestry of placental mammals, 51 Williams, J. Leon, cited on three types of central upper in- cisors, 138, Fig. 73, 139 Williston, S. W., contributions to paleontology, 86 Williston’s law, illustrated, Figs. 48-52, 78-82; loss of oper- cular series, example of, 114 Wolf, marsupial (Thylacinus), under side of skull of, Fig. 53, 85; dentary of, Fig. 21, 37 Worm, annelid, head of, 6; flat- worm, 6, Fig. 2, facing 6 Wyoming, Notharctus found in Eocene formations of, 54 Yerkes, R. M., cited on agreement of mental traits in man and anthropoid, 74; Fig. 39 copied from photograph by, facing 64 Zalambdalestes, skull and restora- tion of head, Fig. 29, 50 Ziska, Mrs. Helen, drawings made by, 86 Zygomatic arch, foreshadowed in Mycterosaurus, 34; origin of human, 89 295 4 Per. 4S Ae a