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diff --git a/.gitattributes b/.gitattributes new file mode 100644 index 0000000..6833f05 --- /dev/null +++ b/.gitattributes @@ -0,0 +1,3 @@ +* text=auto +*.txt text +*.md text diff --git a/44541-0.txt b/44541-0.txt new file mode 100644 index 0000000..74d9551 --- /dev/null +++ b/44541-0.txt @@ -0,0 +1,3026 @@ +*** START OF THE PROJECT GUTENBERG EBOOK 44541 *** + + THE LAST LINK + + OUR PRESENT KNOWLEDGE OF THE + DESCENT OF MAN + + BY + + ERNST HAECKEL + (JENA) + + WITH NOTES AND BIOGRAPHICAL SKETCHES + + BY + + HANS GADOW, F.R.S. + (CAMBRIDGE) + + + LONDON + ADAM AND CHARLES BLACK + 1898 + + + +CONTENTS + + + PAGE + THE LAST LINK + + INTRODUCTORY 1 + + COMPARATIVE ANATOMY 8 + + PALÆONTOLOGY 20 + + OTHER EVIDENCE 42 + + STAGES RECAPITULATED 47 + + BIOGRAPHICAL SKETCHES: + + LAMARCK, SAINT-HILAIRE, CUVIER, BAER, + MUELLER, VIRCHOW, COPE, KOELLIKER, GEGENBAUR, + HAECKEL 80 + + THEORY OF CELLS 115 + + FACTORS OF EVOLUTION 117 + + GEOLOGICAL TIME AND EVOLUTION 135 + + + + NOTE + + +The address I delivered on August 26 at the Fourth International +Congress of Zoology at Cambridge, 'On our Present Knowledge of the +Descent of Man,' has, I find, from the high significance of the theme +and the general importance of the questions connected with it, excited +much interest, and has led to requests for its publication. Hence this +volume, edited by my friend Dr. H. Gadow, my pupil in earlier days, +who has not only revised the text, but has also enriched it by many +valuable additions and notes. + + ERNST HAECKEL. + +_Jena, December, 1898._ + + + + + THE LAST LINK + + +At the end of the nineteenth century, the age of 'natural science,' the +department of knowledge that has made most progress is zoology. From +zoology has arisen the study of transformism, which now dominates the +whole of biology. Lamarck[1] laid its foundation in 1809, and forty +years ago Charles Darwin obtained for it a recognition which is now +universal. It is not my task to repeat the well-known principles of +Darwinism. I am not concerned to explain the scientific value of the +whole theory of descent. The whole of our biological study is pervaded +by it. No general problem in zoology and botany, in anatomy and +physiology, can be discussed without the question arising, How has this +problem originated? What are the real causes of its development? + + [1] See note, p. 80. + +This question was almost unknown seventy years ago, when Charles +Darwin, the great reformer of biology, began his academical career at +Cambridge as a student of theology. In the same year, 1828, Carl Ernst +von Baer[2] published in Germany his classical work on the embryology +of animals, the first successful attempt to elucidate by 'observation +and reflection' the mysterious origin of the animal body from the +egg, and to explain in every respect the 'history of the growing +individuality.' Darwin at that time had no knowledge of this great +advance, and he could not divine that forty years later embryology +would be one of the strongest supports of his own life's work--of that +very theory of transformism which, founded by Lamarck in the year of +Darwin's birth, was accepted with enthusiasm by Charles's grandfather +Erasmus. There is no doubt that of all the celebrated naturalists of +the nineteenth century Darwin achieved the greatest success, and we +should be justified in designating the last forty years as the Age of +Darwin. + + [2] See note, p. 89. + +In searching for the causes of this unexampled success, we must clearly +separate three sets of considerations: first, the comprehensive reform +of Lamarck's transformism, and its firm establishment by the many +arguments drawn from modern biology; secondly, the construction of the +new theory of selection, as established by Darwin, and independently +by Alfred Wallace (a theory called Darwinism in the proper sense); +thirdly, the deduction of anthropogeny, that most important conclusion +of the theory of descent, the value of which far surpasses all the +other truths in evolution. + +It is the third point of Darwin's theory that I shall discuss here; and +I shall discuss it chiefly with the intention of examining critically +the evidence and the different conclusions which at present represent +our scientific knowledge of the descent of man and of the different +stages of his animal pedigree. + +It is now generally admitted that this problem is the most important +of all biological questions. Huxley was right when in 1863 he called +it the question of questions for mankind. The problem which underlies +all others, and is more deeply interesting than any other, is as +to the place which man occupies in nature and his relations to the +universe of things. 'Whence our race has come; what are the limits of +our power over nature, and of nature's power over us; to what goal are +we tending--these are the problems which present themselves anew and +with undiminished interest to every man born into the world.' This +impressive view was explained by Huxley thirty-five years ago in his +three celebrated essays on 'Evidence as to Man's Place in Nature.' The +first is entitled 'On the Natural History of the Man-like Apes'; the +second, 'On the Relations of Man to the Lower Animals'; the third, 'On +some Fossil Remains of Man.' Darwin himself felt the burden of these +problems as much as Huxley; but in his chief work, 'On the Origin of +Species,' in 1859, he had purposely only just touched them, suggesting +that the theory of descent would shed light upon the origin of man and +his history. Twelve years later, in his celebrated work on 'The Descent +of Man, and Selection in Relation to Sex,' Darwin discussed fully and +ingeniously all the different sides of this 'question of questions' +from the morphological, historical, physiological, and psychological +points of view. As early as 1866 I myself had applied in the _Generelle +Morphologie der Organismen_ the theory of transformism to anthropology, +and had shown that the fundamental law of biogeny claims the same +value for man as for all the other animals. The intimate causal +connection between ontogeny and phylogeny, between the development of +the individual and the history of its ancestors, enables us to gain +a safe and certain knowledge of our ancestral series. I had at that +time distinguished in this series ten chief degrees of vertebrate +organization. I attributed the highest importance to the logical +connection of anthropogeny with transformism. If the latter be true, +the truth of the former is absolute. 'Our theory that man is descended +from lower vertebrates, and immediately from apes or primates, is a +case of special _deduction_ which follows with absolute certainty from +the general _induction_ of the theory of descent.' The full proof and +detailed explanation of this view was afterwards given in my 'History +of Natural Creation,' and especially in my 'Anthropogeny.'[3] Lastly, +it has received an ample scientific and critical foundation in the +third part of my 'Systematic Phylogeny.'[3] + + [3] See notes, pp. 102, 106 + +During the forty years which have elapsed since Darwin's first +publication of his theories an enormous literature, discussing the +_general problems_ of transformism as well as its special application +to man, has been published. In spite of the wide divergence of the +different views, all agree in one main point: the natural development +of man cannot be separated from general transformism. There are only +two possibilities. Either all the various species of animals and +plants have been created independently by supernatural forces (and +in this case the creation of man also is a miracle); or the species +have been produced in a natural way by transmutation, by adaptation +and progressive heredity (and in this case man also is descended from +other vertebrates, and immediately from a series of primates). We are +absolutely convinced that only the latter theory is fully scientific. +To prove its truth, we have to examine critically the strength of the +different arguments claimed for it. + + + + + I. + + +First, we have to consider the relative place which comparative +anatomy concedes to man in the 'natural system' of animals, for the +true value of our 'natural classification' is based upon its meaning +as a pedigree. All the minor and major groups of the system--the +classes, legions, orders, families, genera, and species--are only +different branches of the same pedigree. For man himself, his place +in the pedigree has been fixed since Lamarck,[4] in 1801, defined the +group of vertebrates. The most perfect[5] of these are the Mammalia; +and at the head of this class stands the order of Primates, in which +Linnæus, in 1735, united four 'genera'--Homo, Simia, Lemur, and +Vespertilio. If we exclude the last-named, the Chiroptera of modern +zoology, there remain three natural groups of Primates--the Lemures, +the Simiæ, and the Anthropi or Hominidæ. This is the classification of +the majority of zoologists; but if we compare man with the two chief +groups of monkeys--the Eastern monkeys (or Catarrhinæ) and the Western +or American monkeys (Platyrrhinæ)--there can be no doubt that the +former group is much more closely related to man than is the latter. +In the natural order of the Catarrhinæ we find united a long series +of lower and higher forms. The lowest, the Cynopitheci, appear still +closely related to the Platyrrhinæ and to the Lemures; while, on the +other hand, the tailless apes (Anthropomorphæ) approach man through +their higher organization. Hence one of our best authorities on the +Primates, Robert Hartmann,[6] proposed to subdivide the whole order of +the Simiæ into three groups: (1) Primarii, man together with the other +Anthropomorphæ, or tailless apes; (2) Simiæ, all the other monkeys; (3) +Prosimiæ, or Lemurs. This arrangement has received strong support from +the interesting discovery by Selenka that the peculiar placentation +of the human embryo is the same as in the great apes, and different +from that of all the other monkeys. Our choice between these different +classifications of Primates is best determined by the important thesis +of Huxley, in which, in 1863, he carried out a most careful and +critical comparison of all the anatomical gradations within this order. +In my opinion, this ingenious thesis--which I have called the Huxleyan +Law, or the 'Pithecometra-thesis of Huxley'--is of the utmost value. +It runs as follows: 'Thus, whatever system of organs be studied, the +comparison of their modifications in the ape-series leads to one and +the same result--that the structural differences which separate man +from the gorilla and the chimpanzee are not so great as those which +separate the gorilla from the lower apes.' If we accept the Huxleyan +law without prejudice, and apply it to the natural classification of +the Primates, we must concede that man's place is within the order +of the Simiæ. On examining this relation with care, and judging +with logical persistence, we may even go a step further. Instead of +the wider conception of 'Simiæ,' we must use the restricted term of +Catarrhinæ, and our Pithecometra-thesis has then to be formulated +as follows: _The comparative anatomy of all organs of the group of +Catarrhine Simiæ leads to the result that the morphological differences +between man and the great apes are not so great as are those between +the man-like apes and the lowest Catarrhinæ_. In fact, it is very +difficult to show why man should not be classed with the large apes in +the same zoological family. We all know a man from an ape; but it is +quite another thing to find differences which are absolute and not of +degree only. Speaking generally, we may say that man alone combines the +four following features: (1) Erect walk; (2) extremities differentiated +accordingly; (3) articulate speech; (4) higher reasoning power. Speech +and reason are obviously relative distinctions only--the direct result +of more brains and more brain-power, the so-called mental faculties. +The erect walk is not an absolutely distinguishing characteristic: the +large apes likewise walk on their feet only, supporting their bodies +by touching the ground with the backs of their hands--in fact, with +their knuckles--and this is a mode of progression very different from +that of the tailed monkeys, which walk upon the palms of their hands. +There are, however, two obvious differences in the development of the +muscles. In man alone the gastrocnemius and the soleus muscle are thick +enough to form the calf of the leg, and the glutæus maximus is enlarged +into the buttocks. A fourth glutæal muscle occurs occasionally in +man, while it is constantly present in apes as the so-called musculus +scansorius. Concerning the muscles of the whole body, we cannot do +better than quote Testut's summary: 'The mass of recorded observations +upon the muscular anomalies in man is so great, and the agreement of +many of these with the condition normal in apes is so marked, that the +gap which usually separates the muscular system of man from that of the +apes appears to be completely bridged over.' + + [4] See note, p. 80. + + [5] _Perfect_, in the sense of highest stage of evolution, may seem a + _petitio principii_. Leaving aside the consideration that no living + creature is absolutely perfect, in the sense that its organization + cannot become more efficient or proficient, we have here to deal with + relative perfection of the whole organization. A fish or a snake is in + its way more specialized than a mammal; but specialization does not + necessarily mean height of development: it generally means life in a + comparatively narrow groove. The acts of giving birth and nourishing + the young with the mother's milk is a much higher stage than the act + of laying eggs and letting them run their chance. The development of + a hairy coat goes along with heightened temperature of the blood, + subsequent greater independence of the surrounding temperature, and + increased steady activity of the brain and other nerve-centres. The + brain of the Mammalia, in its minute structure, is much more complex. + This rule applies to some of the principal sense organs, chiefly the + nose and the ear. The skeleton, not so much as a whole as in the + various bones and joints, is more neatly finished, and built up more + in conformity with 'scientific principles,' than is the case even with + birds, in spite of their marvellous specialization. The same is the + case with the vascular system, notably the heart and the veins, and + with the excretory organs. In all of these many imperfections, still + to be found in the other classes, have been corrected in Mammalia. The + Primates take an easy first by their hands, and among them the apes and + man himself by their brains. + + [6] 'Die menschenähnlichen Affen und ihre Organisation im Vergleich zur + menschlichen.' 1883. + +There are, for example, the muscles of the ear. In most people the +majority, or even all of them, are no longer movable at will, while in +the apes they are still in use. The important point, however, is that +these muscles are still present in man, although often in a reduced +condition. They are the following: (1) Musculus auricularis anterior +or attrahens auris, which is frequently much reduced and no longer +reaches the ear at all, being then absolutely useless; (2) Musculus +auricularis superior or attollens auris, more constant than the former; +(3) Musculus auricularis posterior or retrahens auris, likewise often +functional. Occasionally smaller slips differentiated from these +three muscles are present, and as so-called intrinsic muscles are +restricted to the ear itself; their function is, or was, that of +curling up or opening the external ear. + +[Illustration: OUTLINES OF THE LEFT EAR OF-- + +1. _Lemur macaco_; 2. _Macacus rhesus_, the Rhesus monkey; 3. +Cercopithecus, a macaque; 4. human embryo of six months; 5. man, with +Darwin's point well retained: the dotted outline is that of the ear of +a baboon; 6. orang-utan (after G. Schwalbe):[7] ^x the original tip of +the ear; 7. human ear with the principal muscles. + + [7] G. Schwalbe, 'In wiefern ist die menschliche Ohrmuschel ein + rudimentäres Organ?'--In what Respects is the Human Outer Ear a + Rudimentary Organ? (_Archiv f. Anatomie und Physiologie_, 1889).] + +In connection with the ear, I may touch upon another interesting +and most suggestive little feature which is present in many +individuals--namely, 'Darwin's point.' This is the last remnant of the +original tip of the ear, before the outer, upper, and hinder rim became +doubled up or folded in. It is a feature quite useless, and absolutely +impossible of interpretation, excepting as the vestige of such previous +ancestral conditions as are normal in the monkeys. + +In some cases the reduction of muscles has proceeded further in apes +than in man--for example, the muscles of the little toe. Another +instance is afforded by the coccyx or vestige of the tail; this is +still furnished with muscles which are now in man, as well as in +the apes, quite useless, and vary considerably with every sign of +degeneration, most so in the orang-utan. + +Darwin has mentioned the frequent action of the 'snarling muscle,' by +which, in sneering, our upper canine teeth are exposed, like those of a +dog prepared to fight. + +Monkeys and apes possess vocal sacs, especially large in the +orang-utan; survivals of them, although no longer used, persist in man +in the shape of a pair of small diverticula, the pouches of Morgagni, +between the true and the false vocal cords. + +'In the native Australians, the dental formula appears least removed +from the hypothetical original type, for in it are still found complete +rows of splendid teeth, with powerfully-developed canines and molars, +the latter being either uniform, or even increasing in size, as we +proceed backwards, in such a way that the wisdom tooth is the largest +of the series. This is decidedly a pithecoid characteristic which is +always found in apes. The upper incisors of the Malay, apart from their +prognathous disposition, have occasionally a distinctly pithecoid +form, their anterior surface being convex, and their lingual surface +slightly concave. The ancestors of Europeans seem to have had the same +form of teeth, for the oldest existing fragments of skulls from the +Mammoth age (_e.g._, the jaws from La Naulette, in Belgium) reveal +tooth-forms which must be classed with those of the lowest races of +to-day.'[8] + + [8] Wiedersheim, 'Der Bau des Menschen als Zeugniss für seine + Vergangenheit.' Freiburg, 1888. Translated: 'The Structure of Man an + Index to his Past History.' London, 1895. + +Now we are able to apply this fundamental Pithecometra-thesis directly +to the classification of the Primates and to the phylogeny of man, +which is intimately connected with it, because in this order, as in +all the other groups of animals, the natural system is the clear +expression of true phylogenetic affinity. Four results follow from our +thesis: (1) The Primates, as the highest legion or order of mammals, +form one natural, monophyletic group. All the Lemures, Simiæ, and +Homines descend from one common ancestral form, from a hypothetical +'Archiprimas.' (2) The Lemures are the older and lower of the natural +groups of the Primates; they stand between the oldest Placentalia +(Prochoriata) and the true Simiæ. (3) All the Catarrhinæ, or Eastern +Simiæ, form one natural monophyletic group. Their hypothetical +common ancestor, the Archipithecus, may have descended directly or +indirectly from a branch of the Lemures. (4) Man is descended directly +from one series of extinct Catarrhine ancestors. The more recent +ancestors of this series were tailless anthropoids (similar to the +Anthropopithecus), with five sacral vertebræ. The more remote ancestors +were tailed Cercopitheci, with three or four sacral vertebræ. + +These four theses possess, in my opinion, absolute certainty. +They are independent of all future anatomical, embryological, and +palæontological discoveries which may possibly throw more light upon +the details of our phyletic anthropogenesis. + + + + + II. + + +The next question is, how the facts of palæontology agree with these +most important results of comparative anatomy and ontogeny. The fossils +are the true historical 'medals of creation,' the palpable evidence of +the historical succession of all those innumerable organic forms which +have peopled the globe for many millions of years. Here the question +arises, If the known fossil specimens of Mammalia, and particularly +of Primates, give proof of these Pithecometra-theses, do they confirm +directly the descent of man from ape-like creatures? The answer to this +question is, in my opinion, affirmative. + +It is true that the gaps in the palæontological evidence, here as +elsewhere, are many and keenly felt. In the order of the Primates +they are greater than in many other orders, chiefly because of the +arboreal life of our ancestors. The explanation is very simple. It is +really due to a long chain of favourable coincidences if the skeleton +of a vertebrate, covered as it was with flesh and skin, and containing +still more perishable viscera, is petrified at all. The body may be +devoured by other creatures, and its bones scattered about; or it rots +away and crumbles to pieces. Many animals hide in thick undergrowth +when death approaches them; and, leading an almost entirely arboreal +life, the Primates are especially likely to disappear without being +fossilized. It is only when the body is quickly covered with sand, or +is embedded in suitable lime or silica containing mud, that the process +of petrifaction can come to pass. Even then it is only by great good +luck that we come across such a fossil. Very few countries have been +searched systematically, and the areas that have been searched amount +to little in comparison with the whole surface of the land, even if we +leave out of account the fact that more than two-thirds of the globe +are covered by water. + +These deplorable deficiencies of empirical palæontology are balanced +on the other side by a growing number of positive facts, which possess +an inestimable value in human phylogeny. The most interesting and most +important of these is the celebrated fossil _Pithecanthropus erectus_, +discovered in Java in 1894 by Dr. Eugène Dubois.[9] Three years ago +this now famous ape-like man provoked an animated discussion at the +third International Zoological Congress at Leyden. I may therefore +be allowed to say a few words as to its scientific significance. +Unfortunately, the fossil remains of this creature are very scanty: the +skull-cap, a femur, and two teeth. It is obviously impossible to form +from these scanty remains a complete and satisfactory reconstruction of +this remarkable Pliocene Primate. + +[9] _Pithecanthropus erectus._ 'Eine menschenähnliche Uebergangsform +aus Java' ('A Human-like Transitional Form'). Batavia, 1894. + +The more important points are the following: The remains in question +rested upon a conglomerate which lies upon a bed of marine marl and +sand of Pliocene age. Together with the bones of Pithecanthropus were +found those of Stegodon, Leptobos, Rhinoceros, Sus, Felis, Hyæna, +Hippopotamus, Tapir, Elephas, and a gigantic Pangolin. It is remarkable +that the first two of these genera are now extinct, and that neither +hippopotamus nor hyæna exists any longer in the Oriental region. If we +may judge from these fossil remains, the bones of Pithecanthropus are +not younger than the oldest Pleistocene, and probably belong to the +upper Pliocene. The teeth are like those of man. The femur, also, is +very human, but shows some resemblances to that of the gibbons. Its +size, however, indicates an animal which stood when erect not less +than 5 feet 6 inches high. The skull-cap also is very human, but with +very prominent eyebrow ridges, like those of the famous Neanderthal +cranium. It is certainly not that of an idiot. It had an estimated +cranial capacity of about 1,000 cubic centimetres--that is to say, much +more than that of the largest ape, which possesses not more than 600 +c.c. The crania of female Australians and Veddahs measure not more than +1,100, some even less than 1,000 c.c.; but, as these Veddah women stand +only about 4 feet 9 inches high, the computed cranial capacity of the +much taller Pithecanthropus is comparatively very low indeed.[10] + + [10] On the day after the delivery of this address Dr. Dubois exhibited + the cranium of Pithecanthropus, from which he had removed the stony + matrix which filled the inside, in order to examine the impression left + by the cerebral convolutions. He was able to show that they also are + very human, and more highly developed than those of the recent apes. [ + Illustration: The upper figure represents the outlines + of the skull of Pithecanthropus, as restored by Manouvier.[11] The + lower figure shows the comparative size and shape of Pithecanthropus, + the Neanderthal skull, a specimen of the Cro-Magnon race of neolithic + France, and a Young Chimpanzee before the full development of the + supraorbital crests.] + + [11] L. Manouvier: 'Deuxième étude sur le Pithecanthropus erectus comme + précurseur présumé de l'homme.' (_Bulletins de la Soc. d'Anthropologie + de Paris_, 1895.) + +The final result of the long discussion at Leyden was that, of twelve +experts present, three held that the fossil remains belonged to a low +race of man; three declared them to be those of a man-like ape of great +size; the rest maintained that they belonged to an intermediate +form, which directly connected primitive man with the anthropoid +apes. This last view is the right one, and accords with the laws of +logical inference. _Pithecanthropus erectus_ of Dubois is truly a +Pliocene remainder of that famous group of highest Catarrhines which +were the immediate pithecoid ancestors of man. He is, indeed, the +long-searched-for 'missing link,' for which, in 1866, I myself had +proposed the hypothetical genus Pithecanthropus, species Alalus. + +It must, however, be admitted that this opinion is still strongly +combated by some distinguished authorities. At the Leyden Congress it +was attacked by the illustrious pathologist Rudolf Virchow.[12] He, +however, is one of the minority of leading men of science who set +themselves to refute the theory of Evolution in every possible way. For +thirty years he has defended the thesis: 'It is quite certain that man +is not a descendant of apes.' He declares any intermediate form to be +unimaginable save in a dream. + + [12] See Notes, p. 93. + +Virchow went to the Leyden Congress with the set purpose of disproving +that the bones found by Dubois belonged to a creature which linked +together apes and man. First, he maintained that the skull was that +of an ape, while the thigh belonged to man. This insinuation was at +once refuted by the expert palæontologists, who declared that without +the slightest doubt the bones belonged to one and the same individual. +Next, Virchow explained that certain exostoses or growths observable on +the thigh proved its human nature, since only under careful treatment +the patient could have healed the original injury. Thereupon Professor +Marsh, the celebrated palæontologist, exhibited a number of thigh-bones +of wild monkeys which showed similar exostoses and had healed without +hospital treatment. As a last argument the Berlin pathologist declared +that the deep constriction behind the upper margin of the orbits +proved that the skull was that of an ape, as such never occurred in +man. It so happened that a few weeks later Professor Nehring of Berlin +demonstrated exactly the same formation on a human prehistoric skull +received by him from Santos, in Brazil. + +Virchow was, in fact, just as unlucky in Leyden in his fight with our +pliocene ancestor as he had been unfortunate in his opinion on the +famous skulls of Neanderthal, Spy, La Naulette, etc., every one of which +he explained as a pathological abnormality. It would be a very curious +coincidence indeed if all these and other fossil human remains were +those of idiots or otherwise abnormal individuals, provided they are +old and low enough in their organization to be of phylogenetic value to +the unbiassed zoologist. + +As the sworn adversary of Evolution, transformism, and Darwinism in +particular, but a believer in the constancy of species, the great and +renowned pathologist has been driven to the incredible contention that +all variations of organic forms are pathological. + +Four years ago, as honorary president of the Anthropological Congress +at Vienna, he attacked Darwinism in the severest manner, and declared +that 'man may be as well descended from the elephant or from the sheep +as from the ape.' Such attacks on the theory of transformism indicate a +failure to understand the principles of the theory of Evolution and to +appreciate the significance of palæontology, comparative anatomy, and +ontogeny. + +The thousands of other objections which have been made during the last +forty years (chiefly by outsiders) may be passed over in silence. They +do not require serious refutation. In spite of, or perhaps because of, +these attacks, the theory of Evolution stands established more firmly +than ever. + +It is easy for the outsider to exult over the difficulties which our +problem implies--difficulties which we who have given our lives to the +study understand likewise, and try our best not only to bridge over, +but also to point out. Anyhow, we do not conceal them; while those who +reject the explanation offered by Evolution make the most of the gaps, +and pass silently over the far more numerous points favourable to our +theory. + +How fruitful during the last thirty years the astonishing progress in +our palæontological knowledge has been for our Pithecometra-thesis is +best shown by a short glance at the growth of our knowledge of fossil +Primates. Cuvier,[13] the founder of palæontology, continued up to the +time of his death, in 1832, to assert that fossil remains of monkeys +and lemurs did not exist. The only skull of a fossil lemuroid which +he described (namely, Adapis) he declared to be that of an ungulate. +Not until 1836 were the first fragments of extinct monkeys found in +India; it was two years later, near Athens, that the skeleton of +_Mesopithecus penthelicus_ was discovered. Other remains of lemurs were +found in 1862. But during the last twenty years the number of fossil +Primates has been augmented by the remarkable discoveries of Gaudry, +Filhol, Milne Edwards, Seeley, Schlosser, and others in Europe; of +Marsh, Cope, Osborn, Leidy, Ameghino, in South America; and Forsyth +Major in Madagascar.[14] These tertiary remains, chiefly of Eocene and +Miocene date, fill many gaps between existing genera of Primates, and +afford us quite a clear insight into the phyletic development of this +order during the millions of years of the Cænozoic age. + + [13] See notes, p. 87. + + [14] + F. AMEGHINO: 'Contribucion al conocimiento de los mamÃferos + de la república Argentina.' In _Actas de la Academia nacional de + Sciencias en Cordoba_, 1889.--Another article in _Revista Argentina de + Historia natural_. Buenos Aires, 1891. + + A. GAUDRY: 'Animaux fossiles et géologie de l'Attique.' + 1862.--'Le Dryopithèque.' _Mém. Soc. géol. de France_: + 'Paléontologie.' 1890. + + O. MARSH: 'Introduction and Succession of Vertebrate Life in + America.' Address, Amer. Assoc. Adv. Sci., Nashville, 1887. + + H. F. OSBORN: 'The Rise of the Mammalia in North America.' + Address, Amer. Assoc. Adv. Sci., Madison, 1893. + + L. RUETIMEYER: 'Ueber die Herkunft unserer Thierwelt,' Basel, + 1867. + + C. S. FORSYTH MAJOR: 'Fossil Monkeys from Madagascar.' + _Geological Magazine_, 1896. + + M. SCHLOSSER: 'Ueber die Beziehungen der ausgestorbenen + Saeugethierfaunen und ihr Verhaeltniss zur Saeugethierfauna der + Gegenwart.' Biolog. Centralblatt, 1888. + +The most important difference between the two groups of existing +monkeys is indicated by their dentition. Adult man possesses, like +all the other Catarrhine Simiæ, thirty-two teeth, whilst the American +monkeys (the Platyrrhinæ) have thirty-six teeth--namely, one pair of +premolars more in the upper and lower jaws. Comparative odontology +leads us to the phylogenetic conclusion that this number has been +produced by reduction from a still older form with forty-four teeth. +This typical dental formula (three incisors, one canine, four +premolars, and three molars, in each half-jaw) is common to all those +most important older mammals which in the beginning of the Eocene +period constituted the four large groups of Lemuravida, Condylarthra, +Esthonychida, and Ictopsida. These are the four ancestral groups +of the four main orders of Placentalia--namely, of the Primates, +Ungulata, Rodentia, and Carnassia. They seem to be so closely related +by their primitive organization that they may be united in one common +super-order, Prochoriata. + +With a considerable degree of probability, we are led to formulate +the further hypothesis that all the orders of Placentalia--from the +lowest Prochoriata upwards to man--have descended from some unknown +common ancestor living in the Cretaceous period, and that this oldest +placental form originated from some Jurassic group of marsupials. + +Among these numerous fossil Lemures which have been discovered within +the last twenty years, there exist, indeed, all the connecting forms +of the older series of Primates, all the 'missing links' sought for by +comparative odontology. + +The oldest Lemures of the tertiary age are the Eocene Pachylemures, +or Hyopsodina. They possess the complete dentition of the +Prochoriata--namely, forty-four teeth (3.1.4.3/3.1.4.3). Then follow +the Eocene Palæolemures, or Adapida, with forty teeth, they having lost +one pair of incisors in each jaw. To these are attached the younger +Autolemures, or Stenopida, with thirty-six teeth, they thus possessing +already the same dentition as the Platyrrhinæ. The characteristic +dentition of the Catarrhinæ is derived from this formula by the loss of +another premolar. + +These relations are so clear and so closely connected with a +gradual transformation of the whole skull, and with the progressive +differentiation of the Primate-form, that we are justified in saying +that the pedigree of the Primates, from the oldest Eocene Lemures +upwards to man, is now so well known, its principal features so firmly +fixed within the Tertiary age, that there is no missing link whatever. + +Quite different, and much more incomplete, is the palæontological +evidence, if we go further back into the Secondary or Mesozoic age, +and look there for the older ancestors of the mammalian series. There +we meet everywhere with wide gaps, and the scarce fragments of fossil +Mesozoic mammals (excessively rare in the Cretaceous formation) are too +poor to permit definite conclusions as to their systematic position. +Indeed, comparative anatomy and ontogeny lead us to the hypothesis +that the oldest Cretaceous Mammalia--the Prochoriata--are descended +from Jurassic marsupials, and these again from Monotremes. We may +also suppose with high probability that among the unknown Cretaceous +Prochoriata there have been Lemuravida and forms intermediate between +these and the Jurassic Amphitheriidæ, and that these marsupials in +their turn are descendants of Pantotheria or similar monotreme-like +creatures of the Triassic age. Any certain evidence for these +hypotheses is at present still wanting. One important fact, however, +is established--namely, that these interesting and oldest Mammalia--the +Pantotheria of Marsh, the Triassic Dromatheriidæ, and the Jurassic +Triconodontidæ of Osborn--were small insectivorous mammals with a very +primitive organization. Probably they were Monotremes, and may be +derived directly from Permian Sauromammalia, an ill-defined mixture of +Mammalia and Reptilia. + +This generalized characteristic supports our view that _the whole +class of Mammalia is monophyletic_, and that all its members, from +the oldest Monotremes upwards to man, have descended from one common +ancestor living in the older Triassic, or perhaps in the Permian, +age. To acquire full conviction of this important conception, we have +only to think of the hair and the glands of our human skin, of our +diaphragm, the heart and the blood corpuscles without a nucleus, our +skull with its squamoso-mandibular articulation. All these singular +and striking modifications of the vertebrate organization are common +to mammals, and distinguish them clearly from the other Craniota. This +characteristic combination and correlation proves that they have been +developed only _once_ in the history of the vertebrate stem, and that +they have been transferred by heredity from one common ancestor to all +the members of the class of Mammalia. + +The next step, as we trace our human phylogeny to its origin, leads us +further back into the lower Vertebrata, into that obscure Palæozoic +age the immeasurable length of which (much greater than that of the +Mesozoic) may, according to one of the newest geological calculations, +have comprised about one thousand millions of years.[15] + + [15] See note, 'Geological Time and Evolution' p. 134. + +The first important fact we have to face here is the complete absence +of mammalian remains. Instead of these we find in the later Palæozoic +period, the Permian, air-breathing _reptiles_ as the earliest +representatives of Amniota. They belong to the most primitive order +of that class, the Tocosauria; and besides them there were the +Theromorpha, which approach the Mammalia in a remarkable manner. These +reptiles in turn were preceded, in the Carboniferous period, by true +Amphibia, most of them belonging to the armour-clad Stegocephali. +These interesting Progonamphibia were the oldest Tetrapoda, the first +vertebrates which had adapted themselves to the terrestrial mode of +life; in them the swimming fin of fishes and Dipneusta was transformed +into the pentadactyle extremities characteristic of quadrupeds. + +To appreciate the high importance of this metamorphosis, we need only +compare the skeleton of our own human limbs with that of the living +Amphibia. We find in the latter the same characteristic composition as +in man: the same shoulder and pelvic girdle; the same single bone, the +humerus or the femur, followed by the same pair of bones in the forearm +and leg; then the same skeletal elements composing the wrist and the +ankle regions; and, lastly, the same five fingers and toes. + +The arrangement of these bones, peculiar and often complicated, but +everywhere essentially the same in all the Tetrapoda, is a striking +evidence that man is a descendant from the oldest pentadactyle Amphibia +of the Carboniferous period. In man the pentadactyle type has been +better preserved by constant heredity than in many other Mammalia, +notably the Ungulata. + +The oldest Carboniferous Amphibia, the armour-clad Stegocephali, and +especially the remarkable Branchiosauri discovered by Credner, are +now regarded by all competent zoologists as the indubitable common +ancestral group of all Tetrapoda, comprising both Amphibia and Amniota. +But whence this most remote group of Tetrapoda? That difficult question +is answered by the marvellous progress of modern palæontology, and +the answer is in complete harmony with the older results arrived +at by comparative anatomy and ontogeny. Thirty-four years ago Carl +Gegenbaur,[16] the great living master of comparative anatomy, had +demonstrated in a series of works how the skeletal parts of the various +classes of Vertebrata, especially the skull and the limbs, still +represent a continuous scale of phyletic gradations. Apart from the +Cyclostomes, there are the fishes, and among them the Elasmobranchi +(sharks and rays), which have best preserved the original structure in +all its essential parts of organization. Closely connected with the +Elasmobranchi are the Crossopterygii, and with these the Dipneusta or +Dipnoi. Among the latter the highest importance attaches to the ancient +Australian Ceratodus. Its organization and development is now, at last, +becoming well known. This transitional group of Dipnoi, 'fishes with +lungs' but without pentadactyle limbs, is the morphological bridge +which joins the Ganoids and the oldest Amphibia. With this chain +of successive groups of Vertebrata, constructed anatomically, the +palæontological facts agree most satisfactorily. Selachians and Ganoids +existed in the Silurian times, Dipnoi in the Devonian, Amphibia in the +Carboniferous, Reptilia in the Permian, Mammalia in the Trias. These +are historical facts of first rank. They connote in the most convincing +manner that remarkable ascending scale in the series of vertebrates +for our knowledge of which we are indebted to the works of Cuvier and +Blainville, Meckel, Johannes Mueller and Gegenbaur, Owen and Huxley. +The historical succession of the classes and orders of the Vertebrata +in the course of untold millions of years is definitely fixed by the +concordance of those leading works, and this invaluable acquisition is +much more important for the foundation of our human pedigree than would +be a complete series of all possible skeletons of Primates. + + [16] See note, p. 97. + +Greater and more frequent difficulties arise if we penetrate further +into the most remote part of the human phylogeny, and attempt to derive +the vertebrate stem from an older stem of invertebrate ancestors. None +of those had a skeleton which could be petrified; and the same remark +applies to the lowest classes of Vertebrata--to the Cyclostomes and +the Acrania. Palæontology, therefore, can tell us nothing about them; +and we are limited to the other two great documents of phylogeny--the +results of comparative anatomy and ontogeny. The value of their +evidence is, however, so great that every competent zoologist can +perceive the most important features of the most remote portion of our +phylogeny. + +Here the first place belongs to the invaluable results which modern +comparative ontogeny has gained by the aid of the biogenetic law or +the theory of recapitulation. The foundation-stones of vertebrate +embryology had been laid by the works of Von Baer, Bischoff,[17] Remak, +and Koelliker;[18] but the clearest light was thrown upon it by the +famous discoveries of Kowalevsky[19] in 1866. He proved the identity +of the first developmental stages of Amphioxus and the Ascidians, and +thereby confirmed the divination of Goodsir, who had already announced +the close affinity of Vertebrates and Tunicates. The acknowledgment of +this affinity has proved of increasing importance, and has abolished +the erroneous hypothesis that the Vertebrata may have arisen from +Annelids or from other Articulata. Meanwhile, from 1860 to 1872, I +myself had been studying the development of the Spongiæ, Medusæ, +Siphonophora, and other Coelenterata. Their comparison led me to the +statements embodied in the 'Gastræatheorie,' the first abstract of +which was published in 1872 in my monograph of the Calcispongiæ. + + [17] Wilhelm Bischoff of Munich: works on the history of the + development of the rabbit, dog, guinea-pig, roe-deer. 1840-1854. + + [18] See note, p. 96. + + [19] 'Ueber die Entwicklung der einfachen Ascidien,' Mém. Acad. St. + Petersbourg, vii. ser., tome x. (1866). Other papers in 'Archiv f. + Mikroskop. Anatomie,' vii. (1871); xiii. (1877). + +These ideas were carried on and expanded during the subsequent ten +years by the help of many excellent embryologists--first of all by E. +Ray Lankester and Francis Balfour. The most fruitful result of these +widely extended researches was the conclusion that the first stages of +embryonic development are essentially the same in all the different +Metazoa, and that we may derive from these facts certain views on +the common descent of all from one ancestral form. The unicellular +egg[20] repeats the stage of our Protozoan ancestors; the Blastula +is equivalent to an ancestral coenobium of Magosphæra or Volvox; +the Gastrula is the hereditary repetition of the Gastræa, the common +ancestor of all the Metazoa. + + [20] See note, p. 115--Theory of cells. + +Man agrees in all these respects with the other vertebrates, and must +have descended with them from the same common root. + +Particularly obscure is that part of our phylogeny which extends from +the Gastræa to Amphioxus. The morphological importance of this last +small creature had been perceived by Johannes Mueller, who in 1842 +gave the first accurate description of it. It would not, of course, be +correct to proclaim the modern Amphioxus the common ancestor of all the +vertebrates; but he must be regarded as closely related to them, and +as the only survivor of the whole class of Acrania. If the Amphioxidæ +had through some unfortunate accident become extinct, we should not +have been able to gain anything like a positive glimpse at our most +remote vertebrate ancestor. On the one hand, Amphioxus is closely +connected with the early larva of the Cyclostomes, which are the +oldest Craniota, and the pre-Silurian ancestors of the fishes. On the +other hand, the ontogeny of Amphioxus is in harmony with that of the +Ascidians, and if this agreement is not merely coincidental, but due to +relationship, we are justified in reconstructing for both Ascidians +and Amphioxus one common ancestral group of chordate animals, the +hypothetical _Prochordonia_. The modern Copelata give us a remote idea +of their structure. The curious Balanoglossus, the only living form of +Enteropneusta, seems to connect these Prochordonia with the Nemertina +and other Vermalia, which we unite in one large class--Frontonia. + +No doubt these pre-Cambrian Vermalia, and the common root of all +Metazoa, the Gastræades, were connected during the Laurentian period +by a long chain of intermediate forms, and probably among these +were some older forms of Rotatoria and Turbellaria; but at present +it is not possible to fill this wide gap with hypotheses that are +satisfactory, and we have to admit that here indeed are many missing +links in the older history of the Invertebrata. Still, every zoologist +who is convinced of the truth of transformism, and is accustomed to +phylogenetic speculations, knows very well that their results are most +unequal, often incomplete. + + + + +III. + + +Let us now recapitulate the ancestral chain of man, as it is set forth +in the accompanying diagram (p. 55), which represents our present +knowledge of our descent. For simplicity's sake the many side-issues +or branches which lead to groups not in the main line of our descent +have been left out, or have been indicated merely. Many of the stages +are of course hypothetical, arrived at by the study of comparative +anatomy and ontogeny; but an example for each of them has been taken +from those living or fossil creatures which seem to be their nearest +representatives. + +1. The most remote ancestors of all living organisms were living beings +of the simplest imaginable kind, organisms without organs, like +the still existing _Monera_. Each consisted of a simple granule of +protoplasm, a structureless mass of albuminous matter or plasson, like +the recent Chromaceæ and Bacteriæ. The morphological value of these +beings is not yet that of a cell, but that of a cytode, or cell without +a nucleus. Cytoplasm and nucleus were still undifferentiated. + +I assume that the first Monera owe their existence to spontaneous +creation out of so-called anorganic combinations, consisting of carbon, +hydrogen, oxygen, and nitrogen. An explanation of this hypothesis I +have given in my 'Generelle Morphologie.' + +The Monera probably arose early in the Laurentian period. The oldest +are the Phytomonera, with vegetable metabolism. They possessed the +power (characteristic of plants) of forming albumin by synthesis from +carbon, water, and ammonia. From some of these plasma-forming Monera +arose the plasmophagous Zoomonera with animal metabolism, living +directly upon the produce of their plasmodomous or plasma-forming +sisters. This is the first instance of the great principle of division +of labour. + +2. The second stage is that of the _simple and single cell_, a bit +of protoplasm with a nucleus. Such unicellular organisms are still +very common. The _Amoebæ_ are their simplest representatives. The +morphological value of such beings is the same as that of the egg +of any animal. The naked egg cells of the sponges creep about in an +amoeboid fashion, scarcely distinguishable from Amoeba. The same +remark applies to the egg-cell of man himself in its early stages +before it is enclosed in a membrane. The first unicellular organisms +arose from Monera through differentiation of the inner nucleus from the +outer protoplasm. + +3. Repeated division of the unicellular organism produces the +_Synamoebium_, or community of Amoebæ, provided the divisional +products, or new generations of the original cell, do not scatter, +but remain together. The existence of such a _Coenobium_, a number +of equal and only loosely-connected cells, as a separate stage in the +ancestral history of animals, is made highly probable by the fact that +the eggs of all animals undergo after fertilization such a process of +repeated self-division, or 'cleavage,' until the single egg cell is +transformed into a heap of cells closely packed together, not unlike a +mulberry (_morula_)--hence _morula_ stage in ontogeny. + +4. The morula of most animals further changes into a _Blastula_, a +hollow ball filled with fluid, the wall being formed by a single layer +of cells, the blastoderm or germinal layer. This modification is +brought about by the action of the cells--they conveying nourishing +fluid into the interior of the whole cell colony and thereby +being themselves forced towards the surface. The Blastula of most +Invertebrata, and even that of Amphioxus, is possessed of fine ciliæ, +or hair-like processes, the vibrating motion of which causes the whole +organism to rotate and advance in the water. Living representatives of +such Blastæads, namely, globular gelatinous colonies of cells enclosing +a cavity, are Volvox and Magosphæra. + +5. The Blastula of most animals assumes a new larval form called +_Gastrula_, in which the essential characteristics are that a portion +of the blastoderm by invagination converts the Blastula into a cup +with double walls, enclosing a new cavity, the primitive gut. This +invagination or bulging-in obliterates the original inner cavity of +the Blastula. The outer layer of the Gastrula is the ectoderm, the +inner the endoderm; both pass into each other at the blastoporus, or +opening of the gut cavity. The Gastrula is a stage in the embryonic +development of the various great groups of animals, and some such +primitive form as ancestral to all Metazoa is thus indicated. This +hypothetical _Gastræa_ is still very essentially represented by the +lower Coelenterates--_e.g._, Olynthus, Hydra. + +6. The sixth stage--that of the _Platodes_, or flat-worms--is very +hypothetical. They are bilateral gastræads, with a flattened oblong +body, furnished with ciliæ, with a primitive nervous system, simple +sensory and reproductive organs, but still without appendages, body +cavity, vent, and blood-vessels. The nearest living representatives of +such creatures are the acoelous Turbellarians--_e.g._, Convoluta, a +free-swimming, ciliated creature. + +7. The next higher stage is represented by such low animals as the +_Gastrotricha_--_e.g._, Chætonotus among the Rotatoria, which differ +from the rhabdocoelous Turbellarians chiefly by the formation of +a vent and the beginnings of a coelom, or cavity, between gut and +body wall. The addition of a primitive vascular system and a pair of +nephridia, or excretory organs, is first met with in the _Nemertines_. + +8. These, together with the _Enteropneusta_ (Balanoglossus), are +comprised under the name of Frontonia, or Rhynchelminthes, and form the +highest group of the Vermalia. + +The Enteropneusta especially fix our attention, because they alone, +although essentially 'worms,' exhibit certain characteristics which +make it possible to bridge over the gulf which still separates the +Invertebrata from the vertebrate phylum. The anterior portion of the +gut is transformed into a breathing apparatus--hence Gegenbaur's +term of Enteropneusta, or Gut-breathers. Moreover, Balanoglossus and +Cephalodiscus possess another modification of the gut--namely, a +peculiar diverticulum, which, in the present state of our knowledge, +may be looked upon as the forerunner of the chorda dorsalis. + +9. Stage of _Prochordonia_, as indicated by the larval form, called +Chordula, which is common to the Tunicata and all the Vertebrata. +These two groups possess three most important features: (_a_) A chorda +dorsalis, a stiff rod lying in the long axis of the body, dorsally from +the gut and below the central nervous system. This latter, for the +first time in the animal kingdom, appears in the shape of a spinal +cord. (_b_) The use of the anterior portion of the gut for respiratory +purposes. (_c_) The larval development of the Tunicata is essentially +the same as that of the Vertebrata in its early stages. Only the +free-swimming Copelata or Appendicularia among the Tunicates retain +most of these features. The others, which become sessile--namely, the +Ascidiæ, or sea-squirts--degenerate and specialize away from the main +line. + +10. Stage of the _Acrania_, represented by Amphioxus. The early +development of this little marine creature agrees closely with +that of the Tunicates; but one important feature is added to its +organization--namely, metamerism, segmentally arranged mesoderm. +Amphioxus still possesses neither skull nor vertebræ, neither ribs +nor jaws, and no limbs. But it is a member of the Vertebrata if we +define these as follows: Bilateral symmetrical animals with segmentally +arranged mesoderm, with a chorda dorsalis between the tubular nervous +system and the gut, and with respiratory organs which arise from the +anterior portion of the gut. We do not assume that Amphioxus stands +in the direct ancestral line; it is probably much specialized, partly +degenerated, and represents a side-branch; but it is, nevertheless, +the only creature, hitherto known, which satisfactorily connects the +Vertebrata with their invertebrate ancestors. Many other efforts have +been made to solve the mystery of the origin of the Vertebrata--all +less satisfactory than the present suggestion, or even absolutely +futile. This remark applies especially to the attempts to derive them +from either Articulata or Echinoderms. The other great and highly +developed phylum, the Mollusca, is quite out of the question. We have +to go back to a level at which all these principal phyla meet, and +there we find the Vermalia, the lower of which alone permit connection +in an upward direction with the higher phyla. + + ANCESTRAL TREE OF THE VERTEBRATA. + + _Abridged from 'Systemat. Phylogenie,' § 15._ + + Names underlined refer to hypothetical groups. + + _Mammalia_ + _Aves_ | + | _Reptilia_ | + | | | + +----------------+ | + | | + +--------------+ + | + _Proreptilia_ + | _Amphibia_ + _Pisces_ | | + | | +----------+ + | | | + | | | _Dipnoi_ + | _Stegocephali_ | + | | | + | +---------------+ + | | + +---------------+ + | _Cyclostomata_ + _Proselachii_ | + | | + _Tunicata_ | +--------+ + | | | + | *_Archicrania_* + | | _Acrania_ + | | | + | *_Prospondylia_*------+ + | | + +----------+ | + | | + *_Prochordonia_* + + +11. Stage of _Cyclostomata_. This now small group of Lampreys and +Hagfishes represents the lowest Craniota; and although much specialized +as a side-branch of the main-stem from which the other Craniota have +sprung, they give us an idea of what the direct ancestors of the latter +must have been like:--still without visceral arches, without jaws and +without paired limbs; with a persistent pronephros; the ear with one +semicircular canal only; mouth suctorial; cranium very primitive; +and the metamerism of the vertebral column indicated only by little +blocks of cartilage in the perichordal sheath. Such creatures must +have existed at least as early as the Lower Silurian epoch; but until +1890 fossil Cyclostomes were unknown. Their life in the mud, or as +endoparasites of fishes, coupled with their soft structure, makes them +very unfit for preservation. This gives all the greater importance to +Traquair's discovery, in 1890, of many little creatures, called by him +_Palæospondylus gunni_, in the Old Red Sandstone of Caithness, which +seem to be very closely allied to Cyclostomata. + +12. The _Elasmobranchi_ (sharks and skates), with their immediate +forerunners, the Acanthodi of the Devonian and Carboniferous age, +are the first typical fishes. That they existed as far back as the +Silurian age is proved by many enamelled spines of the dermal armour, +chiefly from the dorsal fins. This higher stage is characterized by the +possession of typical jaws, by visceral or gill-bearing arches, and by +two pairs of limbs. None of the Elasmobranchs, fossil or recent, stands +in the direct ancestral line; but they are the lowest Gnathostomata, +jaw-and-limb-possessing creatures, known. + +13. Closely connected with the Elasmobranchs in a wider sense are the +_Crossopterygii_, which begin in the Devonian age as a large group, but +have left only two survivals, the African Polypterus and Calamoichthys. +They are possessed of dermal bones and other ossifications, and are +characterized by their lobate paired fins, which have a thick axis +beset with biserial fin rays. Their gill-clefts are covered by an +operculum, and they have a well-developed air-bladder. Whilst they +are in many respects more highly developed than the Elasmobranchs, +and are intimately connected with the typical Ganoids and other +bony fishes (all of which form a great, manifold side-branch of the +general vertebrate stem), they stand in many other respects (notably, +the structure of the paired fins, the vertebral column, and the +air-bladder) nearer the main-stem of our own ancestral line. + +14. This is shown by their intimate relation to the _Dipnoi_, which +are still represented by the Australian, African, and South American +mud-fishes: Ceratodus, Protopterus, and Lepidosiren. The genus +Ceratodus existed in the Upper Trias, whence various other unmistakably +dipnoous forms lead down through the Carboniferous (_e.g._, Ctenodus) +to the Devonian strata--_e.g._, Dipterus. They are characterized as +follows: The paired fins still retain the archipterygial form (namely, +one axis with biserial rays); the heart is already trilocular, and +receives blood which is mixed arterial and venous, owing to the gills +being retained, while the air-bladder has been modified into a lung. In +fact, the generalized Dipnoi form the actual link between fishes and +_Amphibia_. + +15. _Amphibia._ The earliest amphibian fossils occur in +the Carboniferous strata. They alone--the Stegocephali or +Phractamphibia--stand in the ancestral line, while the Lissamphibia, to +which all the recent forms belong, are side-branches. The Stegocephali +are the earliest Tetrapoda, the archipterygial paired fins having been +transformed into the pentadactyle fore and hind limbs, which are so +characteristic of all the higher Vertebrata. The cranium is roofed +over by dermal bones, of which, besides others, supra-occipitals, +supra-orbitals, and supra-temporals are always present. The lowest +members (Branchiosauri) still retained gills besides the lungs, while +others (Microsauri) have lost the gills. Be it remembered that all +the recent Amphibia still undergo the same metamorphosis during their +ontogenetic development. + +In the very important Temnospondyli, a subgroup of the +Stegocephali--_e.g._, Trimerorhachis of the Lower Red Sandstone or +Lower Permian--the component cartilaginous or bony units which compose +the vertebræ still remained in a separate, unfused state, showing at +the same time an arrangement whence has arisen that which is typical +of the Amniota. The same applies to the limbs and their girdles. In +fact, the Stegocephali, taken as a whole, lead imperceptibly to the +_Proreptilia_. + +16. _Proreptilia_ are represented by the Permian genera Eryops and +Cricotus. Until quite recently these and many other fossils from +the Carboniferous strata were looked upon as Amphibia, while many +undoubted fossil Amphibia were mistaken for reptiles, as indicated by +the frequent termination '-saurus' in their names. + +The nearest living representative of these extinct Proreptilia is +the New Zealand reptile Hatteria, or Sphenodon, close relations +of which are known from the Upper Trias; while others--_e.g._, +Palæohatteria--have been discovered in the Permian. Anyhow, Sphenodon +is the reptile which stands nearest to the main stem of our ancestry. + +The most important characteristics of the Reptilia, which mark a higher +stage or level, are (1) The entire suppression of the gills--although +during the embryonic development the gill-clefts still appear in all +reptiles, birds, and mammals; (2) The development of an amnion and an +allantois, both for the embryonic life only, but so characteristic +that all these animals are comprised under the name of Amniota; +(3) The articulation of the skull with the first neck vertebræ by +well-developed condyles, either single (really triple) or double (such +a condylar arrangement begins with the Amphibia, but only the two +lateral condyles are developed, while the middle portion, belonging to +the basi-occipital element, remains rudimentary[21]); (4) The formation +of centra, or bodies of the vertebræ, mainly by a ventral pair of the +original quadruple constituents, or arcualia. + + [21] Similar conditions seem to have prevailed among the Proreptilia; + but in those of their descendants which have specialized into Reptiles + and Birds the basi-occipital element becomes more and more predominant + in that formation which ultimately leads to the apparently single + condyle. Hence it is misleading to divide the Tetrapoda into the two + main groups of Amphi-and Mono-condylia, and therefrom to conclude that + the two-condyled Mammalia are more closely related to the likewise + amphicondylous Amphibia than to the so-called monocondylous Reptiles. + +17. Between the Proreptilia and the Mammalia, which latter occur in +the Upper Triassic epoch, we have necessarily to intercalate a group +of very low reptiles, which are still so generalized that their +descendants could branch off either into the Reptilia proper or into +the Mammalia. The changes concerned chiefly the brain and the heart; +of the skeleton, the skull and the pelvis; and, of the tegumentary +structures, the formation of a hairy covering. Many such creatures +existed in the Triassic epoch--namely, the _Theromorpha_--some of which +indeed possess so many characteristics which otherwise occur in the +Mammalia only, that these creatures have been termed _Sauro-Mammalia_. +However, it has to be emphasized that none of the Theromorpha hitherto +discovered fulfils all the requirements which would entitle them to +this important linking position. They only give us an approximate idea +of what this link was like. + +18. Stage of the _Promammalia_, or _Prototheria_. The only surviving +members are the famous duck-bill, Ornithorhynchus, and the spiny +ant-eaters, Echidna and Proechidna, of the Australian region. These +few genera, however, differ so much from one another in various +important respects that they cannot but be remnants of an originally +much larger group. Indeed, many fossils from the Upper Triassic and +from the Jurassic strata have without much doubt to be referred to the +Prototheria. The Prototheria are typical mammals, because they possess +the following characteristics: The heart is completely quadrilocular; +the blood is warm, and its red corpuscles have, owing to the loss +of their nucleus, been modified from biconvex into biconcave discs; +they have a hairy coat and sweat glands, and two occipital condyles; +the ilio-sacral connection is preacetabular; the ankle-joint is +cruro-tarsal; the quadrate bone of the Reptilia has ceased to carry the +under jaw, which now articulates directly with the squamosal portion +of the skull. Their low position is shown by the retention of the +following reptilian features: Complete coracoid bones and a T-shaped +interclavicle; a cloaca, or common chamber for the passage of the +fæces, the genital and the urinary products; they are still oviparous; +the embryo develops without a chorion, and is therefore not nourished +through a placenta. Even the milk glands, which are absolutely +peculiar to the Mammalia, are still in a very primitive stage, and do +not yet produce milk proper; and there is only a temporary shallow +marsupium. + +19. Stage of _Metatheria_, or _Marsupialia_, are direct descendants of +Prototheria; but they show higher development by the reduction of the +coracoid bones and the interclavicle. The original cloaca is divided +into a rectal chamber and a uro-genital sinus, completely separated, +at least in the males; they are viviparous; the young are received +into a permanent marsupium, in the walls of which are formed typical +milk glands and nipples, but the embryo is still devoid of a placenta, +although some recent marsupials show indications of such an organ. The +corpus callosum in the brain is still very weak. + +Most of the marsupials are extinct. They occur from the Upper Trias +onwards, and had in the Jurassic epoch attained a wide distribution +both in Europe and in America. Since the Tertiary epoch they have +been restricted to America and to the Australian region, and are now +represented by about 150 species. + +20. Stage of _Prochoriata_, or early _Placentalia_: a further +development of the Metatheria by the development of a placenta, loss +of the marsupium and the marsupial bones, complete division by the +perineum of the anal and uro-genital chambers, stronger development of +the corpus callosum, or chief commissure of the two hemispheres of the +brain. + +Placentalia must have come into existence during the Cretaceous +epoch. Up to that time all the Mammalia seem to have belonged to +either Prototheria or to Metatheria; but in the early Eocene we can +distinguish the main groups of Placentalia--namely, (1) Trogontia, now +represented by the rodents; (2) Edentata, or sloths, armadilloes, etc.; +(3) Carnassia, or Insectivora and Carnivora; (4) Chiroptera, or bats; +(5) Cetomorpha, or whales and dugongs; (6) Ungulata; (7) Primates. +Of these groups, the first and second, third and fourth, fifth and +sixth, can perhaps, to judge from palæontological evidence, be combined +into three greater groups, as indicated by the fossil Esthonychida, +Ictopsida, and Condylarthra, in addition to the ancestral Primates, +or Lemuravida, as the fourth large branch of the ancestral-tree where +this has reached the placental level. Among none of the first three +branches can we look for the ancestors of the Primates. The Lemuravida, +therefore, represent a branch equivalent to the three other branches. + +21. Stage of _Lemures_, or _Prosimiæ_, comprising the older members of +the Primates, consequently approaching most nearly to the Lemuravida. +The limbs are modified into pentadactyle hands and feet of the arboreal +type, and are protected by nails. The dentition is of the frugivorous +or omnivorous type, with an originally complete series of teeth, with +milk teeth and with permanent. The orbit is surrounded by a complete +bony ring, posteriorly by a fronto-jugal arch, but still widely +communicating with the temporal fossa. The placenta is diffuse and +non-deciduous. + + ANCESTRAL TREE OF THE MAMMALIA. + + _'Systematische Phylogenie,' § 386._ + + _Perissodactyla_ _Homo_ _Carnivora_ + | (_Litopterna_) | | _Pinnipedia_ + | | | | | + +-------+ _Anthropoidae_ +------+ + _Artiodactyla_ | | | + | | | _Carnassia_ + +----------+ _Catarhinæ_ | + | | _Chiroptera_ | + _Proboscidea_ | | | _Insectivora_ | + | | _Platyrhinæ_ | | | + (_Amblypoda_) | | | | +-------+ + | | | | | | _Rodentia_ + +-------+ | _Simiæ_ +-------+ | + | | | | (_Tillodontia_) + +--+ | | | + _Cetacea_ | | | _Trogontia_ + | _Sirenia_ | _Lemures_ _*Ictopsales*_ | _Edentata_ + | | | | | | | + _Cetomorpha_ | _Hyracoidea_ | | _*Esthonychales*_ + | | | | | | + +---_?_---+------+ | | | + | _*Lemuravidæ*_ | | + _*Condylarthrales*_ | +-------+ | + | | | | + +--------Eutheria s. Placentalia------------------+ + | + | _Marsupialia polyprotodontia_ + _Marsupialia diprotodontia_ | | + | | | + +-------------Metatheria--------------+ + | + | _Monotremata_ + | | (_Allotheria_) + | | | + | +-----------------+ + | | + Prototheria-----+ + | + | + _*Hypotheria s.*_ _*Promammalia*_ + + _Names in brackets indicate extinct groups. + Names *underlined* indicate hypothetical groups or combinations._ + +22. Stage of _Simiæ_. Orbit completely separated from the temporal +fossa by an inward extension of the frontal and malar bones meeting the +alisphenoid. Placenta consolidated into a disc, and with a maternal +deciduous portion. Mammæ pectoral only. The dental formula is 2.1.3.3. +All the fingers and toes are protected by flat nails. The tail is long. +The American prehensile-tailed monkeys are a lower side-branch. + +23. Stage of _Catarrhinæ Cercopithecidæ_. The dental formula is +2.1.2.3, owing to the loss of one pair of premolars in each jaw. +The frontal and alisphenoid bones are in contact, separating the +parietal from the malar bone; this feature is correlated with the +enlarged brain. The internarial septum is narrow, and the nostrils +look forwards and downwards instead of sidewards--hence the term +'Catarrhinæ.' The external auditory meatus is long and bony. The tail +is long, with the exception of _Macacus inuus_. The body is covered +with a thick coat of furry hair. Catarrhine monkeys have existed, we +know with certainty, since the Miocene. + +24. Stage of _Catarrhinæ Anthropoidæ_, or _Apes_. Now represented by +the large apes--namely, the Hylobates or gibbon of South-Eastern Asia, +_Simia satyrus_, the orang-utan of Sumatra and Borneo, _Troglodytes +gorilla_, _T. niger_ and _T. calvus_, the gorilla and the chimpanzees +from Western Equatorial Africa. Of fossils are to be mentioned +Pliopithecus and Dryopithecus from European Miocene, and _Troglodytes +sivalensis_ from the Pliocene of the Punjaub. The tail is reduced +to a few caudal vertebræ, which are transformed into a coccyx, not +visible externally; but in the embryos of apes and man the tail is +still a conspicuous feature. The walk is semierect; in adaptation +to the prevailing arboreal life, the arms are longer than the legs. +The hair of the body is considerably more scanty than in the tailed +monkeys. _Troglodytes calvus_, a species or variety of chimpanzee, is +bald-headed. None of the recent genera of apes can lay claim to a place +in the ancestry of mankind. + +25. Stage of _Pithecanthropi_. Hitherto the only known representative +is _Pithecanthropus erectus_, from the Upper Pliocene of Java. In +adaptation to a more erect gait, the legs have become stronger and the +hind-hand has been turned into a flat-soled walking 'foot.' The brain +is considerably enlarged. Presumably it is still devoid of so-called +articulate speech; this is indicated by the fact that children have +to learn the language of their parents, and by the circumstance that +comparative philology declares it impossible to reduce the chief human +languages to anything like one common origin. + +26. _Man._ Known with certainty to have existed as an implement-using +creature in the last Glacial epoch. His probable origin cannot, +therefore, have been later than the beginning of the Plistocene. The +place of origin was probably somewhere in Southern Asia. + +Whilst we have to admit that there are great defects in the older +(invertebrate) portion of our pedigree, we have all the more reason to +be satisfied with the positive results of our investigation of the more +recent (vertebrate) part of it. All modern researches have confirmed +the views of Lamarck, Darwin, and Huxley, and they allow of no doubt +that the nearest vertebrate ancestors of mankind were a series of +Tertiary Primates. + +Particularly valuable are the admirable attempts of the two zoologists, +Paul and Fritz Sarasin,[22] to throw light upon the human phylogeny by +painstaking comparison of all the skeletal parts of man with those of +the anthropoid apes. They have shown that among the lower races of man +the primitive Veddahs of Ceylon approach the apes most nearly, and that +among the latter the chimpanzee stands nearest to man. + + [22] 'Ergebnisse naturwissenschaftlicher Forschungen auf Ceylon,' vols. + 4 and 5. (With an atlas of 84 plates; 1893.) + +The direct descent of man from some extinct ape-like form is now beyond +doubt, and admits of being traced much more clearly than the origin +of many another mammalian order. The pedigrees of the Elephants, the +Sirenia, the Cetacea, and, above all, of the Edentata, for example, +are much more obscure and difficult to explain. In many parts of their +organization--for example, in the number and structure of his five +digits and toes--man and monkeys have remained much more primitive than +most of the Ungulata. + +The immense significance of this positive knowledge of the origin of +man from some Primate does not require to be enforced. Its bearing +upon the highest questions of philosophy cannot be exaggerated. Among +modern philosophers no one has perceived this more deeply than Herbert +Spencer.[23] He is one of those older thinkers who before Darwin were +convinced that the theory of development is the only way to solve +the 'enigma of the world.' Spencer is also the champion of those +evolutionists who lay the greatest weight upon _progressive heredity_, +or the much combated _heredity of acquired characters_. From the first +he has severely attacked and criticised the theories of Weismann, who +denies this most important factor of phylogeny, and would explain +the whole of transformism by the 'all-sufficiency of selection.' In +England the theories of Weismann were received with enthusiastic +acclamation, much more so than on the Continent, and they were called +'Neo-Darwinism,' in opposition to the older conception of Evolution, +or 'Neo-Lamarckism.' Neither of those expressions is correct. Darwin +himself was convinced of the fundamental importance of progressive +heredity quite as much as his great predecessor Lamarck; as were also +Huxley and Spencer. + + [23] 'Principles of Biology': 'The Factors of Organic Evolution'; 'The + Inadequacy of Natural Selection.' + +Three times I had the good fortune to visit Darwin at Down, and on each +occasion we discussed this fundamental question in complete harmony. +I agree with Spencer in the conviction that progressive heredity is +an indispensable factor in every true monistic theory of Evolution, +and that it is one of its most important elements. If one denies with +Weismann the heredity of acquired characters, then it becomes necessary +to have recourse to purely mystical qualities of germ-plasm. I am of +the opinion of Spencer, that in that case it would be better to accept +a mysterious creation of all the various species as described in the +Mosaic account. + +If we look at the results of modern anthropogeny from the highest point +of view, and compare all its empirical arguments, we are justified in +affirming that _the descent of man from an extinct Tertiary series of +Primates is not a vague hypothesis, but an historical fact_. + +Of course, this fact cannot be proved _exactly_. We cannot explain all +the innumerable physical and chemical processes, all the physiological +mutations, which have led during untold millions of years from the +simplest Monera and from the unicellular Protista upwards to the +chimpanzee and to man. But the same consideration applies to all +historical facts. We all believe that Aristotle, Cæsar, and King Alfred +did live; but it is impossible to give a proof within the meaning of +modern exact science. We believe firmly in the former existence of +these and other great heroes of thought, because we know well the works +they have left behind them, and we see their effects in the history +of human culture. These indirect arguments do not furnish stronger +evidence than those of our history as vertebrates. We know of many +Jurassic mammals only a single bone, the under jaw. We all believe that +these mammals possessed also an upper jaw, a skull, and other bones. +But the so-called 'exact school,' which regards the transformation of +species as a hypothesis not proven, must suppose that the mandibula was +the only bone in the body of these curious animals. + +Looking forward to the twentieth century, I am convinced that it will +universally accept our theory of descent, and that future science +will regard it as the greatest advance made in our time. I have no +doubt that the influence of the study of anthropogeny upon all other +branches of science will be fruitful and auspicious. The work done in +the present century by Lamarck and Darwin will in all future times be +considered one of the greatest conquests made by thinking man. + + EVOLUTIONARY STAGES OF THE PRINCIPAL GROUPS OF VERTEBRATA.[24] + + STAGES OF THE CLASSES. STAGES OF THE HEART. + PAIRED LIMBS. + + { 1. _Acrania._ I. _Leptocardia._ + I. _Adactylia_ { Cold-blooded; heart + s. _Impinnata_. { with one chamber; + Without jaws { without lungs. + and limbs. { + { 2. _Cyclostomata._ } II. _Ichthyocardia._ + } Cold-blooded; heart + } two-chambered, with + } one atrium and one + } ventricle; heart + } containing venous + } blood only; without + II. _Polydactylia_ { 3. _Pisces._ } lungs. + s. _Pinnata_. { + With two { } III. _Amphicardia._ + pairs of fins. { 4. _Dipnoi._ } Cold-blooded; heart + } with three complete + } chambers, namely, with + } two atria and one + } ventricle, or (Reptilia) + { 5. _Amphibia._ } two ventricles with still + { } incomplete septum; heart + { } containing mixed venous + { } and arterialized + III. _Pentadactylia_ { 6. _Reptilia._ } blood; with lungs. + s. _Tetrapoda_. { + With two pairs { { IV. _Thermocardia._ + of pentadactyle { { Warm-blooded; heart + limbs (unless { 7. _Aves._ { with four complete + they have { { chambers, namely, two + been lost by { { auricles and two + reduction). { { ventricles; right half + { { of the heart with venous, + { { left half with + { { arterialized, blood; with + { 8. _Mammalia._ { lungs. + + + [24] Abridged from Haeckel's 'Systematische Phylogenie der + Vertebraten,' § 14. + + + + + BIOGRAPHICAL SKETCHES + + +JEAN BAPTISTE DE MONET, CHEVALIER DE LAMARCK, was born on +August 1, 1744, in Picardy, where his father owned land. Originally +educated for the Church, he soon enlisted, and distinguished himself +in active service. Owing to an accident affecting his health, the +young Lieutenant gave up the military career, and, without means, +studied medicine and natural sciences at Paris. In 1778 appeared his +'Flore française.' In 1793 he was appointed to a Chair of Zoology at +the newly-formed Musée d'Histoire Naturelle. He had the misfortune to +become gradually blind, and the last years of his life were spent amid +straitened circumstances. He died in 1829. + +In 1794 Lamarck divided the whole animal kingdom into vertebrate and +invertebrate animals, and founded successively the groups of Crustacea, +Arachnida, Annelida, and Radiata. Between 1816 and 1822 he published +his celebrated 'Histoire naturelle des Animaux sans Vertèbres.' + +His most famous work is the 'Philosophie zoologique,' 1809. + +Assuming the spontaneous origin of life, he propounded the doctrine +that all animals and plants have arisen from low forms through +incessant modifications and changes. In this respect he was in absolute +opposition to Cuvier, who upheld the immutability of species, and did +his best by absolute silence to suppress the spread of the new doctrine. + +Lamarck has explained his views of transformism chiefly in the seventh +chapter of the first volume of his 'Philosophie zoologique.' + +Organisms strive to accommodate or adapt themselves to new +circumstances, or to satisfy new requirements--_e.g._, climate, mode +of procuring food, escape from enemies. The continued function of +parts of an organism changes the old and produces new organs. The +acquirements are inherited by the offspring, and thus are produced the +more complicated from simpler organisms. Continued disuse brings about +degeneration and ultimate loss of an organ. + +Lamarck consequently sees in the adaptability, or power of adaptation, +which he assumes for all living matter the ultimate cause of variation; +and, as he was certainly the first to point out that acquired +characters are inherited by the progeny, he has given a working +explanation of Evolution. + +But his doctrine did not spread--partly because he was misunderstood. +His theory, that a new want, by making itself felt, exacts from the +animal new exertions, perhaps from parts hitherto not used, until the +want is satisfied--this way of putting it sounds too teleological +to explain the yearned-for change in a mechanical or natural way. +Moreover, many of his examples lacked the exact basis of experiment +and observation necessary for their acceptance. Witness that of the +neck of the giraffe,--a never-failing source of ridicule to men who +cannot see the deeper purpose underlying the well-meant attempt at +an explanation, which failed from want of complete knowledge of the +intricate circumstances. + +However, the theory of transformism was, so to speak, in the air; +and various authors have written on the subject, filling the gap +between Lamarck and Darwin, especially Goethe, Treviranus, Leopold +von Buch, and Herbert Spencer. But it is Darwin's immortal merit to +have opened our eyes by his theory of natural selection, which is, at +least, the first attempt to explain some of the causes and incidents +of organic Evolution in a natural mechanical way. Moreover, he was +the first clearly to express the fundamental principles of the theory +of descent, to elaborate what had been at best a general sketch of an +ill-defined problem, and to enter into detail, supported by a host +of painstaking observations, the making of which had taken him half a +lifetime. Darwin, without going further than cursorily into the causes +of variation, argued as follows: We know that variations do occur +in every kind of living creatures. Some of these variations lead to +something, while others do not. An enormously greater number of animals +and plants are born than reach maturity and can in their turn continue +the race. What is the regulating factor? His answer is, The struggle +for existence--in other words, the weeding out of the less fit, or +rather of the owners of those variations which are not so well adapted +to their surroundings. + +For 'adapted' we had better read 'adaptable,' because a variation which +does not answer, which cannot be made use of, or, still more notably, +is a hindrance or disadvantage, does not become an adapted feature. +There is often a confusion between adaptation as an accomplished +fact, a feature, or resultant condition, and adaptation as the mode +of fitting the organism to, or making the best of, the prevailing +surroundings or circumstances. + +ÉTIENNE GEOFFROY SAINT-HILAIRE was born in 1772 at Étampes, +Seine-et-Oise. He was originally brought up for the Church; but when +already ordained he attended lectures on natural science and medicine +in Paris. He managed to get the place of assistant in the Musée +d'Histoire Naturelle; he became Professor of Zoology in 1793, and took +the opportunity of encouraging young Cuvier. Later he became Professor +of Zoology of the Faculté des Sciences, and in 1818 he published his +remarkable 'Philosophie anatomique.' He died in 1844. + +He had conceived the 'unity of organic composition,' meaning that there +is only one plan of construction,--the same principle, but varied in +its accessory parts. In 1830, when Geoffroy proceeded to apply to the +Invertebrata his views as to the uniformity of animal composition, +he found a vigorous opponent in Cuvier. Geoffroy, like Goethe, held +that there is in Nature a law of compensation, or balancing of growth, +so that if one organ take on an excess of development, it is at the +expense of another part; and he maintained that, since Nature takes no +sudden leaps, even organs which are superfluous in any given species, +if they have played an important part in other species of the same +family, are retained as rudiments, which testify to the permanence +of the general plan of creation. It was his conviction that, owing +to the conditions of life, the same forms had _not_ been perpetuated +since the origin of all things, although it was not his belief that +existing species were becoming modified. Cuvier, on the other hand, +maintained the absolute invariability of species, which, he declared, +had been created with regard to the circumstances in which they were +placed, each organ contrived with a view to the function it had +to fulfil,--thus putting the effect for the cause ('Encyclopædia +Britannica,' 9th edition, vol. xxi., p. 171). + +GEORGE CUVIER was born in 1769 at Montbéliard, in the department of +Doubs, which at that time belonged to Württemberg. He was educated at +Stuttgart, and studied political economy. While acting as private tutor +to a French family in France he followed his favourite pursuit, the +study of natural sciences. Geoffroy Saint-Hilaire heard of him, and +appointed him assistant in the department of comparative anatomy in the +Musée d'Histoire Naturelle. In 1799 he was elected Professor of Natural +History at the Collège de France, and soon after he became Perpetual +Secretary of the Institut National. In 1831, a year before his death, +Louis Philippe raised him to the rank of a peer of France. + +Cuvier was the first to indicate the true principle upon which the +natural classification of animals should be based--namely, their +structure. It is the study of the anatomy of the creatures and their +comparison which affords the only sound basis of a classification. +The work which had the greatest influence upon the scientific public +is his 'Règne animal distribué d'après son Organisation,' 1817. The +system which he propounded in this book gradually came to have almost +world-wide fame, and, in spite of its many obvious deficiencies, still +lingers in some of our most recent text-books. + +A standard work is his 'Leçons d'Anatomie comparée,' and, in truth, he +is the founder of that kind of comparative anatomy which was brought +to such a high state by his pupil, the late Sir Richard Owen. Cuvier +discovered the law of 'correlation of growth,' and was the first to +apply this law to the reconstruction of animals from fragments: see his +monumental work entitled 'Recherches sur les Ossemens fossiles,' 1812. + +Cuvier, however, as a strict matter-of-fact man, was incapable of +appreciating the speculative conclusions which were drawn by his +contemporaries Saint-Hilaire and Lamarck. On the contrary, he firmly +stuck to the doctrine of the immutability of species; and, in order to +account for the existence of animals whose kind exists no longer, he +invented the famous doctrine of successive cataclysms. + +KARL ERNST VON BAER was born in 1792 in Esthonia, studied at Dorpat +and then at Würzburg, where Döllinger introduced him to comparative +anatomy. For a few years he was a _Privat-docent_ at Berlin; then he +went to Königsberg as Professor of Zoology and Embryology. In 1834 +he became an Academician at St. Petersburg, where for many years he +was occupied with the most varied studies, chiefly geographical and +ethnological. The last years of his long, active life he spent in +contemplative retirement on his paternal estate, and he died at Dorpat +in 1876. + +While still at Würzburg he induced his friend Pander, a young man +of means, to study the development of the chick; and Pander was the +first to start the theory of the germinal layers from which all the +organs arise. Baer, however, continued these researches in Königsberg, +and after nine years' labour produced his epoch-making work, 'Ueber +Entwicklungsgeschichte der Thiere: Beobachtung und Reflexion,' +Königsberg, 1828. Nine years later he completed the second volume. +He established upon a firm basis the theory of the germinal layers, +and by further 'reflexions' arrived at the elucidation of some of the +most fundamental laws of biology. For example, in the first volume +he made the following prophetic statement: 'Perhaps all animals are +alike, and nothing but hollow globes at their earliest developmental +beginning. The farther back we trace their development, the more +resemblance we find in the most different creatures. And this leads to +the question whether at the beginning of their development all animals +are essentially alike, and referable to one common ancestral form. +Considering that the "germ" (which at a certain stage appears in the +shape of a hollow globe or bag) is the undeveloped animal itself, we +are not without reason for assuming that the common fundamental form is +that of a simple vesicle, from which every animal is evolved, not only +theoretically, but historically.' + +This statement is all the more wonderful when we consider that the +cells, the all-composing individual units, were not discovered until +ten years later. + +In 1829 Baer discovered the human egg, and later the chorda dorsalis. +In an address delivered in 1834, entitled 'The Most Universal Law +of Nature in all Development,' he explained that only from a most +superficial point of view can the various species be looked upon as +permanent and immutable types; that, on the contrary, they can be +nothing but passing stages, or series of stages, of development, which +have been evolved by transformation out of common ancestral forms. + +JOHANNES MUELLER, born at Coblenz in 1801, established himself +as _Privat-docent_ at Bonn, where in 1830 he became Professor of +Physiology. In 1833 he accepted the Chair of Anatomy and Physiology at +Berlin, where he died in 1858. + +He was one of the most distinguished physiologists and comparative +anatomists. By summarizing the labours and discoveries already made in +the field of physiology, by reducing them to order, and abstracting the +general principles, he became the founder of modern physiology. But +he was scarcely less distinguished by his researches in comparative +anatomy. His 'Vergleichende Anatomie der Myxinoiden,' in _Abhandlungen +der Berliner Akademie_, 1835-45, and 'Ueber die Grenzen der Ganoiden' +(_ibid._, 1846), are standard works of lasting value. + +Mueller exercised a stimulative influence as a teacher. Many well-known +men--such as Helmholtz, Gegenbaur, Bruecke the physiologist, Guenther +the zoologist, Virchow the pathologist, Koelliker and Haeckel--have +been his pupils. + +RUDOLPH VIRCHOW was born in 1821 at Schievelbein, a small +town in Eastern Pomerania. He studied medicine in Berlin as a pupil +of Johannes Mueller, and went in 1849 to Würzburg, where, under the +influence of Koelliker, and Leydig the pathologist, he laid the +foundation of an entirely new branch of medical science--that of +'cellular pathology.' Since 1856 he has filled the principal Chair of +Pathology at Berlin. In 1892 he received the Copley medal of the Royal +Society. + +'His contributions to the study of morbid anatomy have thrown light +upon the diseases of every part of the body; but the broad and +philosophical view he has taken of the processes of pathology has +done more than his most brilliant observations to make the science of +disease. + +'In pathology, strictly so called, his two great achievements--the +detection of the cellular activity which lies at the bottom of +all morbid as well as normal physiological processes, and the +classification of the important group of new growths on a natural +histological basis--have each of them not only made an epoch in +medicine, but have also been the occasion of fresh extension of science +by other labourers' (Proc. Royal Soc., 1892). + +Virchow has not confined himself to medicine. He takes the keenest +interest in anthropology and ethnology, on which subjects he has +contributed many papers. Together with his colleagues Helmholtz the +physicist, and Du Bois Reymond the physiologist, he has taken a leading +place in the spreading of natural science; but, unfortunately, he +did not take to the doctrine of Evolution, and for the last thirty +years has been its declared antagonist, rarely missing an opportunity +of denouncing everything but descriptive anatomy and zoology as the +unsound speculations of dreamers. This has on more than one occasion +brought him into sharp conflict with Haeckel. His activity is +astonishing, especially if it be remembered that Virchow has for many +years been one of the most conspicuous leaders of the Progressists and +Radicals in the German Parliament and Berlin town-council. + +EDWARD DRINKER COPE was born at Philadelphia, Pa. After studying at +several Continental Universities, especially at Heidelberg, he became +first Professor of Natural Science at Haverford College, and later +Professor of Geology and Mineralogy. He died at an early age in 1897. +As a member of various geological expeditions and other surveys, he +explored chiefly Kansas, Wyoming, and Colorado; and he published many +most suggestive papers on the fossil vertebrate fauna of North America, +and on classification especially of Amphibia and Reptiles. + +Among works of a more general philosophical scope may be mentioned 'The +Origin of the Fittest,' 1887, and his latest work, 'The Primary Factors +of Organic Evolution,' 1896. + +ALBERT VON KOELLIKER, born in 1817, became Professor of Anatomy at +Würzburg. His earlier studies and discoveries contributed considerably +to the systematic development of the cell theory. In 1844 he observed +the division and further multiplication of the original egg cell. Next +year he showed the continuity between nerve cells and nerve fibres in +the Vertebrata; later, that the non-striped or smooth muscular tissue +is composed of cellular elements. He demonstrated that the Gregarinæ +are unicellular creatures. In 1852 he went with his younger friend +Gegenbaur to Messina, where he studied especially the development +of the Cephalopoda (cuttlefishes and allies); and he produced a +magnificent work on Alcyonaria, Medusæ, and other allied forms. He +elucidated the development of the vertebral column, especially with +reference to the notochord. + +In 1848 he founded, together with Th. von Siebold, the famous +_Zeitschrift für wissenschaftliche Zoologie_. + +A standard work on mammalian embryology is his 'Entwicklungsgeschichte +des Menschen und der höheren Thiere,' a text-book of which the second +edition appeared in 1879. + +At the anniversary meeting of 1897 he received the Copley medal, the +highest honour which the Royal Society can bestow. + +CARL GEGENBAUR was born on August 21, 1826, in Bavaria. He studied +medicine and kindred subjects in Würzburg, and as a pupil of Johannes +Mueller in Berlin. + +In 1852 he went with Koelliker to Messina to study the structure and +development of the marine fauna. Important papers on Siphonophora, +Echinoderms, Pteropoda, and, later, Hydrozoa and Mollusca, were the +result. Soon after his return he was offered the chair of Anatomy at +Jena, and at this retired spot he produced his most important works, +devoting himself more and more to the study of the Vertebrata. Since +1875 he has held the Chair of Anatomy at Heidelberg. + +In 1859 he published his 'Principles of Comparative Anatomy'; but in +1870 he remodelled it completely, the theory of descent being the +guiding principle. These 'Grundzüge' were followed by a somewhat more +condensed 'Grundriss,' the second edition of which was published +in 1878, and has been translated into French and English. In the +meantime he had broken new ground by the development and treatment of +certain problems concerning the composition and origin of the limbs, +the shoulder-girdle and the skull, researches which are embodied in +his 'Untersuchungen zur vergleichenden Anatomie der Wirbelthiere,' +1864-65-72. + +In 1883 he brought out a text-book on human anatomy. This also marked +a new epoch, because for the first time, not only the nomenclature, +but also the general treatment of human anatomy, was put upon a firm +comparative anatomical basis. The success of this work is indicated by +the fact that it reached the sixth edition in 1897. + +Lastly, in 1898, appeared the first volume of what may be called his +crowning work, 'Vergleichende Anatomie der Wirbelthiere.' + +Gegenbaur is universally recognised, not only as the greatest living +comparative anatomist, but also as the founder of the modern side of +this science, by having based it on the theory of descent. + +In 1896 he received from the Royal Society the Copley medal 'for +his pre-eminence in the science of comparative anatomy or animal +morphology.' + +His marvellously powerful influence as a teacher and investigator has +made Heidelberg a centre whence many pupils have spread his teaching, +and above all his method of research. + +ERNST HEINRICH HAECKEL was born on February 16, 1834, at Potsdam. He +carried out his academical studies alternately at Berlin and Würzburg, +attracted by such men as Johannes Mueller, Koelliker, and Virchow. +For years he was undecided what his career should be, whether that +of botanist, collector, or geographical traveller. Certainly that of +medicine attracted him least, although in deference to his father's +wishes he qualified and settled down for a year's practice in Berlin. +As he himself has told us, he might perhaps have proved rather +successful as a physician, to judge from the fact that he did not lose +a single patient. But 'I had only three patients all told, and the +reason of this is perhaps that I had given on my plate the hours of +consultation as from 5 to 6 _a.m._' + +During the year 1859 he travelled as medical man and artist in Sicily. +In 1861 he was induced by Gegenbaur, whose acquaintance he had made in +Würzburg, to establish himself as a _Privat-docent_ for comparative +anatomy in Jena. And there he has remained ever since, filling the +Chair of Zoology, and having declined several much more tempting offers +from the Universities of Würzburg, Vienna, Strassburg, and Bonn. + +Within one year, 1865, he wrote the two volumes of his 'Generelle +Morphologie der Organismen,' as he himself relates, in order to master +his sorrow over the loss of his first wife. But he broke down, and went +to the Canaries to recruit health and strength. The 'Morphologie,' +which has long been out of print,[25] made scarcely any impression. It +was ignored, probably because he had placed the old-fashioned study of +zoology and morphology upon a thoroughly Darwinistic basis. + +[25] That this great work is now comparatively rare, although still +in the second-hand market, may perhaps be urged in excuse of the +fact of so many attempts made by many authors, both professional and +amateur, to find fault with or to explain the principles of adaptation, +variation, heredity, cænogenesis, phylogeny, etc., in complete +ignorance that all these and many more fundamental questions were fully +discussed more than thirty years ago in the 'Generelle Morphologie.' + +On the advice of his friend Gegenbaur, he gave a more popularly +written abstract of his 'Generelle Morphologie'--in fact, the +substance of a series of his lectures--in the shape of his 'Natürliche +Schöpfungsgeschichte.' This 'History of Natural Creation,' which +in 1898 has reached the ninth edition (first edition translated +into English in 1873), had the desired effect. So also had his +'Anthropogenie oder Entwicklungsgeschichte des Menschen,' the fourth +edition of which appeared in 1891. + +It was a lucky coincidence that Haeckel had just finished his +preliminary academical studies, was entirely at leisure, and +undetermined to which branch of natural science he should devote his +genius, when Darwin's great work was given to the world. Haeckel +embraced the new doctrine fervently, and, as Huxley was doing in +England, he spread it and fought for it with ever-increasing vigour in +Germany. + +With marvellous vigour and quickness of perception he applied the +principles of Evolution or the theory of descent to the whole organic +world, and not only opened entirely new vistas for the study of +morphology, but also worked them out and fixed them. He was the first +to draw up pedigrees of the various larger groups of animals and +plants, filling the gaps by fossils or with hypothetical forms (the +necessary existence of which he arrived at by logical deductions); +and thus he reconstructed the first universal pedigree, a gigantic +ancestral tree, from the simple unicellular Amoeba to Man. Of course +these pedigrees were entirely provisional, as he himself has over and +over again avowed; but they are, nevertheless, the ideal which all +systematists and morphologists working upon the basis of Evolution have +since been seeking to establish. + +Naturally he was vigorously attacked, not only by anti-Darwinians, +or rather anti-Evolutionists, but also by many of those who, having +accepted the principle of transformism, ought to have known better. +Perhaps they thought they did know better. Imperfections or mistakes in +details of the grand attempt,--and these, naturally, were many,--were +singled out as samples of the whole, which was ridiculed as the romance +of a dreamer. + +In the end, however, this hostility, narrow-minded and unfair in +many respects, has done good to the cause. There has arisen an +ever-increasing school of workers in favour of the new doctrine. Owing +to renewed research, criticism, corrections in all directions, we +now know considerably more about natural classification (and this is +pedigree) than when Haeckel first opened out the whole problem. + +Owing to his fearless mode of exposition, regardless of the indignant +wrath which the new doctrine aroused in certain ecclesiastical +quarters, Haeckel bore the brunt of almost endless attacks, and had to +write polemical essays. The result has been that friend and foe alike +are now working on the lines which he has laid down; most of the ideas +which he was the first to conceive, and to formulate by inventing a +scientific terminology for them, have become important branches, or +even disciplines, of the science. + +Most morphologists of the younger generations now take these terms +for granted, without remembering the name of their founder. It is, +therefore, perhaps not quite superfluous to mention some of them: + +_Phylum_, or stem, the sum total of all those organisms which have +probably descended from one common lower form. He distinguished eight +such phyla--Protozoa, Coelenterata, Helminthes or Vermes, Tunicata, +Mollusca, Articulata, and Vertebrata. The phyla are more or less +analogous to 'super-classes,' large branches or 'circles,' or principal +groups of other zoologists. + +_Phylogeny_, the history of the development of these various phyla, +classes, orders, families, and species. + +_Ontogeny_, the history or study of the development of the individual, +generally called embryology. In reality the scope of embryology +is the ontogenetic study of the various species, and this branch +of developmental study alone can be checked by direct, 'exact' +observation, for the simple reason that the individuals alone are +entities, while the species, genera, families, etc., are abstract ideas. + +The _ontogenesis of any given living organism is a short, condensed +recapitulation of its ancestral history or of its phylogenesis_. This +is Haeckel's 'fundamental biogenetic law.' + +A complete proof of the phylogeny of any creature would be given by +the preservation of an unbroken series of all its fossil ancestors. +Such a series will in most cases, for obvious reasons, always remain a +desideratum. In a few cases, however, the desideratum is nearly met: +for example, the ancestral line of the one-toed digitigrade horse from +a four-or five-toed plantigrade and still very generalized Ungulate is +approaching completion. + +Phylogenetic study has to rely upon other help. This is afforded by +comparative anatomy and by the study of ontogeny. If the latter were +a faithful, unbroken recapitulation of all the stages through which +the ancestors have passed, the whole matter would be very simple; but +we know for certain that in the individual development many stages +are left out (or, rather, are hurried through, and are so condensed +by short-cuts being taken that we cannot observe them), while other +features which have been introduced obscure, and occasionally modify +beyond recognition, the original course. + +Again, the sequence of the appearance of the various organs is +frequently upset (_heterochronism_). Some organs are accelerated in +their development, while others, which we know to be phylogenetically +older, are retarded in making their reappearance in the embryo. + +These disturbing or distorting newly introduced features or factors +show themselves chiefly in connection with the embryonic conditions of +growth--for example, yolk-sac, placenta, amnion. They all come within +the category of _cænogenesis_: they are cænogenetic, while the true, +undisturbed recapitulation is _palingenetic_. + +Lastly, some features, so-called rudimentary or vestigial organs, +instead of disappearing, are most tenacious in their recurrence, +while others of originally fundamental importance scarcely leave +recognisable traces, and are, so to speak, only hinted at during the +embryonic growth of the creature we happen to study. Hence arises the +philosophical study of 'Dysteleology.' + +Among other terms invented by Haeckel, and now in general use, are +_Metamere_, _Metamerism_, _Coelom_, _Gonochorism_, _Gastrula_, +_Metazoa_, _Gnathostomata_, _Acrania_, _Craniota_, and _Amniota_. + +Hitherto we have dealt with his general work only, a résumé of which +he gave for many years in a course of thirty lectures before an +audience composed of 'all sorts and conditions of men.' Students of +biology and of medicine side by side with theologians, incipient and +ordained, jurists, political economists, and philosophers, crowded his +lecture-room during the 'seventies to hear the master explaining the +'natural history of creation' or the mysteries of anthropogenesis. +Another course of eighty lectures during the winter semester was, and +still is, devoted to a systematic treatment of zoology, while practical +classes are reserved for the more select. + +His winning personality and fascinating eloquence, combined with a +clear and concise delivery, have gained the enthusiastic admiration of +many a student who went to the quiet University town in order to learn +with his own ears and eyes. + +_List of Separate Publications by Professor Haeckel._ + +'Biologische Studien. I.: Studien ueber die Moneren und andere +Protisten.' Leipzig, 1870 (out of print). He was the first to +make observations on the natural history of the Monera, living +bits of protoplasm, devoid even of a nucleus--_e.g._, _Protogenes +primordialis_, _Protomyxa aurantiaca_. + +'Monographie der Radiolarien.' Berlin, 1862-88. With 171 plates. + +'Entwicklungsgeschichte der Siphonophoren.' Utrecht, 1869. + +'Plankton-Studien. Vergleichende Untersuchungen ueber die Bedeutung und +Zusammensetzung der pelagischen Fauna und Flora.' Jena, 1880. + +'Metagenesis und Hypogenesis von Aurelia aurita.' Jena, 1881. + +'Monographie der Geryoniden oder Ruesselquallen.' Leipzig, 1865. + +'Generelle Morphologie der Organismen.' 2 vols. Berlin, 1866. + +'Anthropogenie oder Entwicklungsgeschichte des Menschen,' 1874; 4th +edition, 1891. + +'Natuerliche Schoepfungs-Geschichte.' 2 vols. Berlin, 1st edition, +1868; 9th edition, 1898. This work has been translated into most +European languages (the first edition in English, under the title +'Natural History of Creation' in 1873; the eighth in 1892). + +'Monographie der Kalkschwaemme.' 3 vols. Berlin, 1872 (out of print). +With the subtitle, 'An Attempt to solve analytically the Problem of +the Origin of Species.' In this work, illustrated by sixty plates, he +showed that the Calcispongia are individually so yielding, so adaptive +to external influences, that it is practically impossible to break up +the whole group into anything like satisfactory species or genera. +According to predilection, we can distinguish either 1 genus with only +3 species, or 3, 21, 43 genera, with 21, 111, 181, or 289 species +respectively. + +In this work, in 1872, Haeckel established the homology of the two +primary layers, ecto- and endoderm, throughout the Metazoa. The attempt +to do the same for the four secondary layers, as made in the second +part of his 'Gastræa-theory,' failed. It caused an enormous amount of +research, hitherto without a satisfactory solution of the problem. + +'Studien zur Gastræa-Theorie.' Jena, 1874. The transformation of +the single primitive egg-cell by cleavage into a globular mass of +cells (Morula)--which latter, becoming hollow (and then known as the +Blastula), turns ultimately by invagination or by delamination into +the Gastrula--is a series of processes which applies to all Metazoa. +The Gastrula is, therefore, the ancestral form of the Metazoa; and the +Gastræa-theory, founded by Haeckel, throws light, on the one hand, upon +the mystery of the phyletic connection of the various animal groups, +while, on the other hand, it connects the Metazoa, or multicellular +organisms, with the lowest Protozoa. We come to this conclusion +becaues the Gastrula arises from and passes through stages which exist as +independent, permanent organisms among the Protozoa. + +Needless to say this Gastræa-theory has been violently attacked in +detail, with the result that various modifications of the Gastrula, +until then undreamed of, have become known. + +'Monographie der Medusen.' Jena, 1879-81. With 72 coloured plates. + +'Reports on the Scientific Results of the Voyage of H.M.S. +_Challenger_.' With 230 plates: + + 1. Deep-sea Medusæ. 1881. + 2. Radiolaria. 1887. + 3. Siphonophoræ. 1888. + 4. Deep-sea Keratosa. 1889. + +A short holiday spent on the coasts of the Red Sea produced the volume +'Arabische Korallen' (Berlin, 1876); and a longer trip to Ceylon has +been described in 'Indische Reisebriefe,' of which the third edition +appeared in 1893. The English translation (1883) is entitled 'A Visit +to Ceylon.' + +'Monism as connecting Religion and Science: the Confession of Faith of +a Man of Science.' 1894. + +Haeckels latest work is the 'Systematische Phylogenie' (Berlin, 1896), +three volumes dealing with Protistæ and Plants, Invertebrata and +Vertebrata. They contain the author's views on the natural system of +the organic world, both living and extinct. Notable in the work are +the many reconstructions of ancestral forms which, provided Evolution +is true, must have existed--hypothetical until they, or something like +them, are found in a fossil state. Everybody who works systematically, +and upon the basis of Evolution, does, sometimes unconsciously, +reconstruct such links, although he may perhaps not see the necessity, +or have the courage to fix his vision, by assigning to it all those +attributes or characters which are indicated by deductions from +comparative anatomy, palæontology, and embryology. + + + + + THEORY OF CELLS. + + +The vegetable cell was discovered by _Schleiden_, Professor of Botany +at Jena, in 1838. Next year _Schwann_ found the animal cell. + +In 1844 _Koelliker_ discovered that the egg cell, by division and +multiplication, becomes an aggregation--a heap of new cells. + +In 1849 _Huxley_ found the two primary layers (observed long before +by _Pander_ and _Baer_ in the chick) also in certain Invertebrata, +the Medusæ; and he called these layers 'ectoderm' and 'endoderm' +respectively. + +In 1851 _Remak_, in his 'Untersuchungen über die Entwicklung der +Thiere,' showed the egg to be a simple cell, and that from it, by +repeated division or multiplication, arise the germinal layers, and +that by differentiation of the cells of these layers are formed all the +tissues of the body. + +_Kowalevsky_, of St. Petersburg, found the two primary germinal layers +also in Worms, Echinoderms, Articulata, and other animals. + +_Haeckel_, in 1872, found the same in the Sponges. He stated that these +two germinal layers occur in all animals, except in the Protozoa; +and that they are homologous, or equivalent, in all the groups of +animals, from the Sponges up to Man. In 1873, in his 'Gastræa-theorie,' +he explained the phylogenetic significance, and tried to show the +homology, of the four secondary germinal layers. + + + + + FACTORS OF EVOLUTION. + + +An organism, as living matter, does not stand in opposition to, +or outside of, the rest of the world. It is part of the world. It +receives matter from its surroundings, and gives some back; therefore +it is influenced by its surroundings. It is acted upon, and it reacts +upon the latter, and if these change (and they are nowhere and never +strictly the same) the organism also _varies_. It _adapts_ itself, and +if it does not, or, rather, cannot, do so, it dies, because it is unfit +to live in the world, or, rather, in those particular surroundings +and conditions in which it happens to be. That organism which yields +most easily, accommodates itself most quickly, has the best chance of +existence--_survival of the fittest_. 'Fitness' in this case does not +mean fitness to live, but rather a particular condition which happens +to fit into the new circumstances. + +Adaptation and variation are simultaneous: they are fundamentally the +same. If there were no adaptability and no variability, those simplest +of organisms which we suppose to have sprung into existence in the +pre-Cambrian period would long ago have ceased to exist. + +It is the physiological momentum which models the organism, and, by +causing its adaptations, has produced its organs by change of function. +Gegenbaur illustrates this most important fundamental truth by an +excellent example. Suppose that, in an absolutely simple organism, all +the parts of its exterior are under the same functional conditions, +so that each part of the surface can take in food, and that this is +digested, assimilated, in the interior. There is, in this condition, +not yet any definite organ. If this organism sinks to the bottom and +becomes sessile, this part is excluded from taking in nourishing +matter, while the opposite surface alone remains, or becomes more, fit +for this function. Thus, a simple variation and adaptation has been +produced, and if the same organism continues in this position, its +bottom cells will estrange themselves from their original function, +while those on the top will convey the food into the interior, where +a cavity will be formed, ultimately with a permanent opening, the +primitive gut and mouth, both very different from the 'foot.' + +Thus, by adaptation and variation the organism acquires new functions, +organs, features, and it gives up and eventually loses others. Its +offspring is like it. Like produces like. This is the principle of +_heredity_. Adaptation, when going on generation after generation on +the same lines in the same direction, becomes continuous, and has an +intensifying, _cumulative_ effect. By always weeding out from a flock +of pigeons those birds which possess more dark feathers than the rest, +we ultimately produce an entirely white race. We hurry on what Nature +does slowly. + +The inheritance of acquired characters becomes very obvious in the +following example: The Monera are the lowest living organisms known; +they consist of a mass of protoplasm, and are still devoid of even +a nucleus. They multiply simply by division; each half is like the +other, and like the parent (which by this process has ceased to exist), +except that each is smaller and has to grow. A certain Moneron, +_Protomyxa aurantiaca_, is orange-coloured, and its offspring is from +the beginning of the same colour, and this colour has been acquired +by that kind of Monera-like protoplasm which thereby has become the +species called Aurantiaca. We have no reason for assuming that there +existed from the beginning of life not only colourless, but also red, +orange, and other kinds of protoplasm. In these simplest of organisms +the whole process of heredity seems very obvious; but in the higher +ones, in those which propagate by eggs, the problem is infinitely +more complicated. It is true that the egg is, strictly, nothing but +a small part of the parental organism, and we know from everyday +experience that this single egg-cell has in it all the attributes and +characteristics of the parent; but these attributes and characteristics +make their appearance successively, just as the egg cell of a chick has +neither wings nor feathers, not even a backbone, but develops these +organs because its parents have them. + +The theory that acquired characters are hereditary has often been +vigorously attacked; but the champions of the negative position have +not given us anything satisfactory instead. They question, also, the +principle of adaptation as a factor in Evolution, and substitute +'variation,' coupled with 'natural selection.' + +They point to Darwin's argument: (1) It is a fact that animals and +plants produce a much greater number of young than in their turn grow +up to propagate the race; (2) no two of the frequently many individuals +of the same breed are exactly alike, although the differences may be +hidden to our perception (this is quite true, because no two entities +can live in absolutely the same place and conditions); (3) through +heredity the offspring takes over the faculties and features of the +parents; (4) what decides which of the many individuals (each one +possessing some aberration or variation) are to live and to propagate +the race?--obviously those individual variations which happen to make +the lucky possessors most fit for the struggle for life. + +So far, well; but the 'Neo-Darwinians' imagine that 'adaptation' +is not the cause, but the result, the effect, of the formation of +species. According to them, the species are neither adapted by, nor do +they adapt themselves to, their surroundings. Adaptation is to them +an accomplished fact, a condition which a species happens to be in +because its particular variation is the one which, to the exclusion of +others, suits or fits into its surroundings. Such a view simply takes +variation for granted, and stipulates it as a something _a priori_, +without raising the further necessary question, why there should be +any variations at all. Why, indeed, unless they are caused by external +influences? Haeckel elucidated this by the conception of adaptation as +explained in the foregoing pages. + +These and kindred speculations have produced some rather curious +discussions, which not infrequently end in conundrums. If we speak of +a case of adaptation as a condition, a fact, we easily run the risk +of getting into confusion about cause and effect. For example: Is the +stag swift because he has long and slender legs, or are his legs long +because he is swift? In reality, swiftness and length of legs are cause +and effect in one. His legs have been so modified as to make him swift, +because he has put them continuously to whatever was his full speed, +which in his thick-footed ancestors was probably a very slow one. The +above question reads, therefore, more sensibly as follows: Has the stag +become swift because his legs have become long and slender, or have his +legs become long and slender because he has attained swiftness? Now, we +see that both halves of the double question are practically the same +and instantly suggest the answer. + +A fundamental difference between artificial machines and living +organisms is that the former are worn out by use, while the latter not +only repair the loss caused by use, but are also stimulated to further +increase. On the other hand, organs which are not put into function, +or are not used, _degenerate_. The various cells of the organ react +upon external stimuli by increased activity. Why this should be so is +another question--perhaps because those which do not would soon be not +fit to survive. Each cell has a function; the more specialized the more +intense it is. Every external stimulus, every contact with the outer +surroundings, is an insult, necessarily of detrimental effect, as it +disturbs the equilibrium of the cell body. It must, therefore, be of +advantage to the cells' well-being to return as soon as possible to the +_status quo ante_, and this can only be done by increased activity. + +In the present state of our knowledge, we can approach only the +simplest cases of acquisition of characteristics. Mostly they are +so complicated, subject to so many unthought-of conditions, that we +do not know from which end to approach the problem. Frequently the +supposed use of certain obvious features is the merest guesswork. This +applies especially to features to which we are not accustomed (although +wrongly so) to assign a function--for example, coloration. A green +tree-frog will with predilection rest on green leaves. The advantages +of concealment are obvious, and in this case he 'adapts himself' to the +surroundings by making for green localities: if he did not he would +be eaten up sooner than his more circumspect comrades. But this making +for, and sitting in, the green has not _necessarily_ made him of that +colour. Extreme advocates of one view would argue as follows: Once upon +a time there were among the offspring of ancestral tree-frogs some +which, among other colours, exhibited green, not much, perhaps not even +perceptible to our eyes. The occurrence of this colour, according to +them, was spontaneous, a freak--as if in reality there were anything +spontaneous in the sense of being causeless. The descendants of these +more greenish creatures, provided they did not pair with frogs of the +ordinary set, became still greener (by accumulative inheritance), and +so on, until the green was pronounced sufficient to be of advantage +when competition could set in. + +With this view there is always the difficulty of understanding how the +initial very small changes can be useful, unless we have to deal with +extremely simple organisms. Is it likely in the case of our frogs that +an almost imperceptible variation in colour makes them more fit to +live? We have to assume that 'luck' or chance kept them for generations +out of harm's reach, until the accumulation of green, hitherto quite +ineffective, neither harmful nor useful, became strong enough to be +effective. Such cases undoubtedly happen. + +But we can also argue out this problem in a somewhat different way, +which goes nearer to the root of the whole process. The original +slight, imperceptible change in pigmentation is not a spontaneous +freak; it was caused by the direct influence of the surroundings in +which the particular frogs happened to live, be this factor light or +temperature or food. Thus it stands to reason that the offspring, +living under similar conditions, will be acted upon in the same way. +That factor which has added green to the parents will add green to the +children, until by accumulative inheritance a more decidedly green +race is produced. + +The offspring of green plants do not become green when grown in the +dark; the young plants inherit not the green, but the capacity of +becoming green when acted upon by sunlight. This as an instance of +direct influence of the surroundings on a substance (chlorophyll), +which has not yet performed a function. But the kittens of a pair of +black cats produce black hair before they are born, and we have no +reason to doubt that the black pigment in their tegumentary structures +is ultimately referable to the action of the sunlight. In many +instances creatures living for generations in darkness become white, +pigmentless, and they regain it when exposed to light. For example, the +white, colourless Proteus from the caves of Adelsberg becomes clouded +grey, and ultimately jet black, when kept in a tank whence light is not +strictly excluded. + +Blindness is a very general characteristic of creatures which dwell in +darkness. There are all stages between total blindness and weak eyes. +Now, do these blind creatures live in darkness because they are blind, +or have they become first weak-eyed and then blind because of the +continuous disuse of their eyes? The former explanation has actually +been suggested! Individuals not smitten, but spontaneously, as a freak, +born with sore eyes, have crept into the darkness for relief and have +produced a blind race! To carry such a notion to the bitter end leads +to absurdities. Anyhow, it is not understandable where the benefit +of losing the eyesight arises. It can be explained only by continued +disuse: witness _Spalax typhlus_, the blind mole, and, above all, the +Endoparasites. + +Let us now take an example to explain the influence of a tangible +external stimulus. Repeated pressure produces callosities. Although +they are not exactly beneficial in the shape of corns on our toes, +they are so on our hands. At any rate, the morphologist can trace the +development of the footpads, nails, hoofs, and horns, step by step from +small beginnings. The cells of the Malpighian stratum, of the inner, +active portion of our epidermis, are excited to extra activity, and +by continually producing more horn cells than peel off the surface of +the skin in the normal process of wear and tear cause the formation +of the pad. It need scarcely be mentioned that hypertrophic growths +are not necessarily useful; they are often harmful, and in that case +pathological. + +Lastly, a few words about the very difficult question of _teleology_. +In trying to explain Evolution in a mechanical--sometimes called +monistic, but in reality natural--way, we exclude anything like a +set purpose, a goal, or ideal, a final condition which the organism +strives to attain. Unknown, however, to many morphologists, especially +embryologists, their writings are full of this teleological notion. +Indeed, there are many cases in which an organism becomes changed, and +quickly, too, in a way which cannot but be called reasonable. It starts +modifications, be they outgrowths, alterations in shape or colour, or +the making good of injuries received, which by 'short-cuts' produce +the only advantageous result that can reasonably satisfy the new +requirement or altered circumstances. + +Trees growing in precarious positions, after part of the supporting +rock has slipped away, throw out new roots, and rearrange some of +the old ones in the only way which could save the tree. In animals +which have lost part of a limb the wound closes up, and what is left +is turned into a serviceable stump--for example, in water-tortoises +(creatures in which reproduction of lost limbs does not happen). In +frogs and newts the lost part is reproduced, not correctly, but in a +good semblance. Tortoises which have had their shell smashed can throw +off an astonishingly large portion and renew the bone as well as the +overlapping scutes; but this mending is not neatly done. It serves the +requirement, but it is patchwork; the new shell is such as no tortoise +ever possessed before. + +Mammals transported into colder countries, or subjected to continued +exposure, grow a thicker coat; and the same kind of tree which in a +sheltered valley is tall, large-leaved, and soft-wooded, assumes a very +different aspect, although perhaps growing into a healthy specimen, +when planted on a wind-exposed hill. + +There is no room, or, rather, no time, to apply to these cases the +principle of many variations or the long-continued accumulation of +infinitely small changes. The thing is to be done quickly, or not +at all. Nor can we explain the mending of a wound, which implies an +activity of countless cells, simply as a case of, or similar to, the +reproduction of a lost part; against such an explanation militates the +almost absolute unlikelihood of that precise injury having happened +before to any of the creature's ancestors. + +Still, I think we are brought near the solution of the mystery by +such considerations. We see no difficulty in the regeneration of a +few cells, or in the making good of the disturbance suffered by one +of the most simple organisms; but we become suspicious when we see +that countless cells, not of one kind, but of the most varied tissues +and parts of the body, make common cause in remedying a defect in a +serviceable way. + +We must assume that since the beginning of life organisms have been +subjected to countless insults. We can scarcely speak of a wound in +an Amæba; but these insults have always been made good, and whenever +this was not the case, that particular organism came to an end. As +these organisms developed into more complicated ones, the possible +insults became more serious, more complicated; and the organisms took +adaptive measures so as to be superior to them. This action, I have +no hesitation in declaring, became by heredity a habit. The whole +creature became so thoroughly 'imbued' (for want of a better word) with +the finding of ways and means for meeting sudden, serious conditions, +that it now acts directly, and produces by a short-cut, with the least +amount of time and with the smallest possible waste of material, that +which meets the occasion, thereby saving the life of the individual +and that of the race. This we cannot but call reasonable and to the +purpose, although it is all carried out by _causæ efficientes_ without +there being any _causæ finales_. + + + + + GEOLOGICAL TIME AND EVOLUTION. + + +One million years is a stretch of time beyond our conception. We can +arrive at a more or less adequate understanding of what a million +individuals or concrete things means. Several Continental nations +can put more than a million men into the field. We can gaze at a +building which contains as many bricks; and we know that our own body +is composed of millions of millions of cells. No such help applies to +time, because that itself is an entirely relative, abstract conception. +We can imagine what one hundred years are like--a span of time +seemingly short to the hale and hearty octogenarian, enormous to the +child, totally inapplicable to certain animals whose whole life is +crowded into one single day. + +Astronomers have long ceased to reckon distances by miles or any +other understandable unit. They express the distances between us and +the stars and nebulæ by 'years of light.' Try to imagine a unit of +length equal to that which is passed through by light (186,000 miles +per second) in one year. Not so very long ago the enormous distances +resulting from astronomical calculations were looked upon as the most +serious objection to the correctness of the astronomers' views as to +the distances which separate our globe from the nearest fixed stars. +We have not yet accustomed ourselves to reckoning time by some similar +broadly-conceived standard--say æons of so many thousand years each. + +Unfortunately, we possess no data whatever for calculating the age +of the successive geological strata. Thanks to Lyell, the theory of +violent universal cataclysms has been done away with. It is more +probable that the same agencies have acted which are now changing +the aspect of the globe; and these changes are slow, as far as we +know them--at least, as far as the formation of sedimentary strata is +concerned, and these alone we have to deal with. Various calculations +have been made, based upon the denudation of the mountains, the +filling up of the valleys by the débris, the formation of deltas, +etc. The results give enormous stretches of time, but all of them +unsatisfactory, because the methods are so very local in their +application. + +The least objectionable attempt is that which, based upon astronomical +calculations, tried to fix the height of the last Glacial epoch[26] at +about 200,000 years ago, and asserted that since its beginning in the +Pliocene epoch as many as 270,000 years have elapsed. The duration +of the whole Tertiary period has by the same authorities been fixed +approximately at 3,000,000 to 4,000,000 years. Beyond this we cannot +venture without the wildest speculation; but we know to a certain +extent the thickness of the various sedimentary strata, which amount +in all to from 100,000 to 175,000 feet--on the average perhaps 130,000 +feet, or about twenty miles. + + [26] James Croll: 'On Geological Time, and the Probable Date of the + Glacial and Upper Miocene Period,' _Philos. Magazine_, xxxv., 1868, pp. + 363-384; xxxvi., pp. 141-154; 362-386. + +Unless we prefer giving up all attempt at calculation as absolutely +hopeless, and thus resign the whole problem, we must at least try to +arrive at some results, and then see if these cannot reasonably be made +use of. + +Neither geologist nor physicist, and no zoologist, would accept the +suggestion that these 130,000 feet of stratified rocks have been +deposited within only as many years, although the average rate of +deposit would in that case be not more than 1 foot per year. On the +other hand, an indignant protest is raised against the assumption of +1,000,000,000 years. + +Lord Kelvin[27] has come to the conclusion (from data which various +other authorities regard as very unsatisfactory) that not much more +than 100,000,000 years can have elapsed since the molten globe acquired +a consolidated crust. Further time must have passed before the surface +had become stable and cool enough to allow the temperature of the +collecting oceans to fall below boiling-point, and it is obvious that +life cannot possibly have begun until after this had happened. + + [27] William Thomson: 'On the Secular Cooling of the Earth,' _Transact. + R. S. Edinb._, xxiii., 1864, pp. 157-169. + +Wallace, in his 'Island Life,' by making use of Professor A. Geikie's +results as to the rate of denudation of matter by rivers from the +area of their basins, and estimating the average rate of deposition, +concludes that 'the time required to produce this thickness of rock +[Professor Haughton's maximum of 177,000 feet] at the present rate +of denudation and deposition is only 28,000,000 years.' Our lower +assumption of 130,000 feet thickness would give only 20,000,000 +years--a rate of 1 foot in 154 years. + +Again, if we prefer round numbers to start with, we have only to +assume that the age of the whole Tertiary period, with its 3,000 feet +thickness, is 3,000,000 years (_i.e._, 1,000 feet in 1,000,000 years, +or 1 foot in 1,000 years, surely an excessively slow rate); then +130,000,000 years would bring us to the bottom of the Laurentian or +pre-Cambrian deposits. Of course, it is a pure assumption that the +same rate of destruction and sedimentation applies to the whole of the +strata; but we know nothing to the contrary, especially if we consider +the average periods, the quick periods of extra activity, taken with +the slow periods or those of standstill. + +Dana estimated the length of the whole Tertiary period at one-fifteenth +of the Mesozoic and Palæozoic combined. If we take the duration of the +Tertiary period, as before, as 3,000,000 to 4,000,000 years, the total +will amount to from 45,000,000 to 60,000,000 years. + +Lastly, Walcott[28] has estimated the duration of the Palæozoic, +Mesozoic, and Cænozoic or Tertiary epochs at about 17,000,000, +7,000,000 and 3,000,000 years respectively, giving 27,700,000 years +from the beginning of the Cambrian; and Williams[29] has calculated the +relative duration of the smaller epochs. See the table on p. 149. + +The results of all these calculations fall surprisingly well within +the limits of Lord Kelvin's allowance. Of course they are based upon +assumptions, but none of them is inherently unreasonable; and it +was my purpose to draw attention to the surprising coincidence in +the closeness of these results, perhaps too good to be true. Such +calculations are considered close enough if they range within a few +multiples of each other. + + [28] 'Geological Time as indicated by the Sedimentary Rocks of North + America.' _Proc. Amer. Assoc. Adv. Sci._, xlii., 1893, pp. 129-169. + + [29] Henry Shaler Williams, 'Geological Biology.' New York, 1895. + +Zoologists have fallen into the habit of requiring enormous lengths of +time for the evolution of the animal kingdom. We know that Evolution is +at best a slow process, and the conception of the changes necessary to +evolve man from monkey-like creatures, these from the lowest imaginary +mammals, these from some reptilian stock, thence descending to Dipnoan +fish-like creatures, and so on back into Invertebrata, down to the +simple Monera--this conception is indeed gigantic. Innumerable, almost +endless, slow changes require seemingly unlimited time, and as time is +endless, why not draw upon it _ad libitum_? + +Huxley pointed out that it took nearly the whole of the Tertiary epoch +to produce the horse out of the four-toed Eohippos, and that, if we +apply this rate to the rest of its pedigree, enormous times would +be required. This is, however, a very misleading statement, which +necessitates considerable reduction, in conformity with our increased +palæontological knowledge. Animals of the genus Equus--namely, +Ungulata, with one toe, and with a certain tooth pattern--from the +Upper Miocene of India are now known. Moreover, it is not simply a +question of the gradual loss of the side-toes. The change from the +fox-sized little Eohippos and Hyracotherium, so far as skull, teeth, +vertebral column, and limbs are concerned (about the soft parts we know +next to nothing), is a very great one indeed. + +Elephants and mammoths seem to have developed very rapidly. None are +known from Eocene strata; but towards the end of the Miocene they had +spread over Asia, Europe, and North America, and that in great numbers. +The Eocene Amblypoda are still so different that we hesitate to connect +them ancestrally with the elephants. + +The Pinnipedia (seals and walruses) are strongly modified fissiped +Carnivora, and have existed since at least the Upper Miocene; the +transformation must have been accomplished within the Miocene period. + +We cannot shut our eyes to the fact that various groups have from the +time of their first appearance burst out into an exuberant growth of +modifications in form, size, and numbers, into all possible--and one +might almost say impossible--shapes; and they have done this within +comparatively short periods, after which they have died out not less +rapidly. It seems almost as if these go-ahead creatures had, by +accepting every possible modification and carrying the same to the +extreme, too quickly exhausted their plasticity--which, after all, +must have limits--thereby becoming unable to meet successfully the +requirements of further changes in their surroundings. The slowly +developing groups, keeping within main lines of Evolution, and not +being tempted into aberrant side-issues, had, after all, a much better +chance of onward evolution. + +A good example of the former are the Dinosaurs. We do not know +their ancestors; but we have here to deal only with their range of +transformation. The oldest known forms occur in the Upper Trias; they +attain their most stupendous development in the Upper Jurassic and in +the Wealden; and they have died out with the Cretaceous epoch. But +already some of their earliest forms had assumed bipedal gait, and the +Oolitic Compsognathus had developed almost bird-like hind-limbs. + +On the other hand, there are many instances of extremely slow +development--facts which raise the difficult question of 'persistent +types.' Are these due to a state of perfection which cannot be improved +upon? Or are they due to a kind of morphological consolidation (not +necessarily specialization) which can no longer yield easily, so that +therefore through changes in their surroundings they may come to an end +sooner than more plastic groups? + +Struthio, the ostrich; Orycteropus, the Cape ant-eater; Tapirus, and +many others, existed in the Miocene age practically as they are +now; but pre-Pliocene dolphins, cats, monkeys, stags, all belong to +closely-allied and well-defined 'genera,' but different from the living +forms. + +Alligators and crocodiles are known from the Upper Chalk; Tomistoma +since the Miocene; Gavialis since the Pliocene. + +The oldest surviving reptile is Sphenodon, the Hatteria of New Zealand, +a fair representative of what generalized reptiles of the later +Triassic period seem to have been like; and to the same period belongs +Ceratodus, the Australian mud-fish, hitherto the oldest known surviving +genus of a very ancient and low type so far as Vertebrata are concerned. + +Now let us see if the above estimates of geological time are so utterly +inapplicable to animal evolution. On purpose we take one of the lowest +estimates, about 28,000,000 years, and apportion them equally to the +various strata or epochs. + +The original owner of the famous Trinil skull, a _Pithecanthropus +erectus_, lived, according to some, in the Late Pliocene, according +to others in the Early Plistocene, period--that is to say, somewhere +about the beginning of our last Glacial epoch, some 270,000 years ago. +Assuming that he and his like reached puberty at sixteen to twenty +years of age, about 17,000 generations would lie between him and +ourselves, or, to put it more forcibly, between him and the lowest +living human races--say the Ceylonese Veddahs. Only 250 generations, +at twenty years, carry us back to 3000 B.C. (_i.e._, beyond +the ken of history); and if it be objected that the differences between +the oldest inhabitants of Egypt, the Naquada, and the present Fellahin +are very slight, we are welcome to multiply these differences sixty +or seventy fold, in order to arrive at the Pithecanthropus level. +But these Naquada had no metal implements, and there cannot be the +slightest doubt that the development of the human race went on by leaps +and bounds after certain discoveries had been made--to wit, the use +of implements and that of fire. That creature which first took up a +stone or a branch and wielded it thereby got such an enormous advantage +over his fellow-creatures that his mental and bodily development went +on apace. The same applies to the improvement of speech. We assume the +single, monophyletic origin of mankind at one place, in one district; +and the differences between some of the races of man are great enough +to constitute what we might call species. Compare the Venus of Milo, +that noble expression of the ancient Greeks' notion of female beauty, +with the 'products of art' of the Veddahs or the dwarfs of Central +Africa, or think of the beau-idéal which a Michael Angelo could +possibly have evolved if he had never seen any but such people. + + _TIME AND EVOLUTION_ + + ====================================================================== + I. |II.| III. | IV. | V. |VI.| VII. + | | | | | |Generations. + -----------+---+-----------+----------+--------------+---+------------ + |} |} |} |Adam and Eve | | 250 + Recent |} 5|} |} |Man, contem- | | 3,500 + Plistocene |} |} |} 270,000| porary with | | + | |} |} | Reindeer | | + | |} |} | in France | | + Pliocene -|} |} 3,000,000| |_Pithecanthro-| 16| 17,000 + |} |} |} 600,000| pus erectus_| | + Miocene -|}10|} |} |Anthropoid | 10| 60,000 + |} |} |}2,100,000| Apes | | + Eocene -|} |} |} |Lemures | 5| 420,000 + | | | | | | + Cretaceous | 10|} | 3,600,000| | | + Jurassic - | 5|} | 1,800,000| | | + Rhætic -|} |} |} |Prototheria, | 3| 1,800,000 + |} |} |} | or first | | + |} |} 7,200,000|} | Mammalia | | + Keuper -|} |} |}1,800,000| | | + Muschel- |} 5|} |} | | | + kalk |} |} |} | | | + New Red |} |} |} |Theromorpha | 4| 425,000 + Sandstone| | | | | | + Magnesian |} |} |} | | | + Limestone|} |} |} | | | + Lower Red |} |} |} |Proreptilia | 4| 250,000 + Sandstone|} |} |}4,000,000| | | + Coal- |}15|} |} |Eotetrapoda | 4| 500,000 + measures |} |} |} | | | + Mountain |} |}17,500,000|} | | | + Limestone | |} | | | | + Devonian -| 15|} | 4,000,000|Dipnoi and | 5| 1,000,000 + | |} | |Crossopterygii| | + Silurian -| 10|} | 2,700,000|First fishlike| 3| 900,000 + | |} | | creatures | | + Ordovician | 10|} | 2,700,000| | | + Cambrian -| 15|} | 4,000,000| Sum total of| | + Laurentian | | | | generations| | --------- + Archæan | | | | (about) | | 5,375,000 + or Meta- | | | | | | + morphic | | | | | | + ====================================================================== + +EXPLANATION OF THE TABLE ON P. 149. + + Column I. contains the names of the successive sedimentary strata. + + " II. contains the percentage of the duration of the various epochs, + according to _Williams_, the time from the Cambrian until recent times + being taken as 100. + + " III. gives the estimated duration in years of the Palæozoic, + Mesozoic, and Cænozoic periods, according to _Walcott_. + + " IV. gives in years the duration of the various smaller epochs, as + computed from Walcott and Williams' statements. + + " V. Representatives of stages of the ancestral line of man. The + names stand in the level of the stratum in which they have made their + first appearance. + + " VI. contains the number of years which, in the present + calculation, have been assumed necessary for the animal to reach + puberty. + + " VII. contains the number of generations which can have elapsed + from stage to stage. For example, 60,000 generations separate the + earliest known anthropoid apes from Pithecanthropus. + +Let us follow the descent of man further back. The next stage, +reckoning backwards, is that from Pithecanthropus to _bonâ-fide_ +anthropoid apes. They are represented in the Miocene by various +genera--_e.g._, Pliopithecus and Dryopithecus. According to Croll and +Wallace, 850,000 years ago carry us into the Miocene epoch. Assuming +that these apes lived about 600,000 years before Pithecanthropus, +namely, in the later half of the Miocene, and taking puberty at ten +years of age, a high estimate, we get not less than 60,000 generations. + +2. From Apes back to lowest Lemurs in the lowest Eocene. The date of +Eocene being fixed at 3,000,000, we have about 2,100,000 years for this +stage; assuming as much as five years for puberty, this results in +420,000 generations. + +3. From Lemures to Prototheria. The earliest known mammalian remains +come from the Rhætic, or top formation of the Triassic epoch; allowing +for the Rhætic only 100,000 years, we have to add the whole of the +Jurassic and Cretaceous, in all about 5,500,000 years. Assuming three +years for a generation, we get 1,800,000 generations. + +4. From Prototheria to something like the Theromorpha at the bottom of +the Triassic strata. A duration of 1,700,000 years divided by four +gives 425,000 generations. + +5. From Theromorpha to Proreptilia, represented by Eryops and Cricotus +from the Lower Permian of Texas. Allowing 1,000,000 years, each +generation at four years, we obtain 250,000 generations. + +6. From Proreptilia to Eotetrapoda, the first terrestrial Vertebrata, +represented by something like the Stegocephali, the earliest of which +are known from the Coal-measures. Assuming them to have come into +existence at the bottom of the Coal-measures, for the duration of which +we may guess 2,000,000 years, we get, with four years' allowance for +puberty, 500,000 generations. + +7. From Eotetrapoda to a not yet separated or differentiated group +of Crossopterygian and Dipnoan fishes, both of which are known from +Devonian strata. The duration of the latter has been computed at +4,000,000 years, which, with 1,000,000 for the Mountain Limestone +formation, gives us 5,000,000 for this stage. Assuming, for the sake +of round numbers, as much as five years for a generation, we get +1,000,000 generations. + +8. Earliest stage, down to the first fish-like creatures. Teeth and +spines indicating the existence of fishes are known from the Upper +Silurian. By carrying the earliest fishes down to the bottom of the +Silurian, with 2,700,000 years' duration, and allowing three years for +attaining puberty, the calculation results in 900,000 generations. + +Further back we cannot go. We do not know of any Vertebrate remains +from the Ordovician and Cambrian, which together represent 6,700,000 +years, enough for at least half as many generations of Prochordate +creatures. The pre-Cambrian or Laurentian epoch lies quite beyond the +reach of calculation, nor have we any trustworthy fossil remains of +living matter from these strata, to which, however, Haeckel and others +refer the first beginnings of life. + +All the above calculations are, of course, only approximate. What we +do know is the existence of representatives of the stages, our proofs +being the fossils; but when we refer the origin of the Eotetrapoda, +for example, to the bottom and not somewhere to the middle of the +Coal-measures, we are guessing merely. Alterations in the levels +assumed for the various stage-representatives will, of course, alter +the result of the number of generations; but the leading idea, as +a whole, is not thereby upset. The fact remains that in the Upper +Silurian we have fishes; from the Coal-measures onwards, fishes and +Amphibia; since the Permian, fishes, Amphibia, and reptiles; since the +end of the Trias these three classes and the Mammalia; and lastly, at +least since the Plistocene, man himself. If Evolution is true at all, +the transformation from early fish-like creatures to man has come about +within these epochs. Being able to assign a time of duration to each +of them, with an approximate total of 21,000,000 years, we are also +able to put the whole ancestral series to a test by expressing each +great stage in generations. The result is very satisfactory. The whole +enormous stretch from the lowest fish-like creatures to man has been +resolved into more than 5,000,000 successive generations, and each of +these means a little step forwards in onward Evolution. + +Nothing is to be gained for the understanding of our problem of +Evolution if we multiply this enormous number of generations by ten +or any other multiple. We are not able to conceive changes so small +as those which necessarily have existed between Pithecanthropus and +man if the whole striking difference is analysed into 17,000 steps. +Every one of these stages in the modifications of the muscles, the +skeletal framework, increase of brain, shortening of the trunk, +lengthening of the legs, improvement of the hands, loss of the hairy +coat, etc., is truly microscopical, imperceptible, just as the +Evolutionist imagines the whole process to have been. Again, where is +the difficulty implied by the change from an air-breathing, in many +structural points half-amphibian, fish into a primitive land-crawling +four-footed creature, if we are allowed to resolve the transformation +into 1,000,000 stages? So far from there being any difficulty, rather +does it appear questionable if so many infinitely small changes have +been necessary to bring about this result. + +One thousand years make apparently no difference in the evolution of +animals, nor does one second change the aspect of the hands on the +face of a clock, nor did Julius Cæsar's commission of scientific men +appreciate the error of about eleven minutes in the length of the year +beyond its real value; but now the Russians are, owing to this neglect, +nearly two weeks behind the civilized nations. + + + THE END. + + + BILLING AND SONS, PRINTERS, GUILDFORD. + + + By PROFESSOR ERNST HAECKEL + + + MONISM; + OR, + The Confession of Faith of a Man of Science. + + Translated from the German by J. D. F. GILCHRIST. + + _Crown 8vo., cloth. Price 1s. 6d. net._ + +'We may readily admit that Professor Haeckel has stated his case with +the clearness and courage which we should expect of him, and that +his lecture may be regarded as a fair and authoritative statement +of the views now held by a large number of scientifically educated +people.'--_Times._ + +'The Monism, which is the substance of his faith, is thus defined by +him: "Our conviction that there lives one spirit in all things, and +that the whole cognizable world is constituted, and has been developed, +in accordance with one common fundamental law." As the confession +of a distinguished man of science, this little work deserves to be +read.'--_North British Daily Mail._ + +'This "Confession of Faith" was delivered by the great German +scientist, its author, as an extemporaneous address at Altenburg +rather more than two years ago. There are, no doubt, a large number of +English readers who will welcome a translation, for this "connecting of +religion and science" has long troubled many earnest students of modern +science.'--_Publisher's Circular._ + +'This is a little book of great daring, an example of the wild +speculative flights of one of the very ablest and greatest of our +contemporary men of science.'--_Aberdeen Free Press._ + +'The address, whatever we may think of its conclusions, is, however, +most interesting reading, and is admirably done into English by the +translator.'--_Literary World._ + + + LONDON: ADAM & CHARLES BLACK, SOHO SQUARE. + + + _Demy 8vo., price 7s. 6d. net._ + + SOURCES OF THE APOSTOLIC + CANONS. + + _With a Treatise on the Origin of the Readership and other Lower Orders._ + + By Professor ADOLF HARNACK. + + Translated by LEONARD A. WHEATLEY. + + _With an Introductory Essay on the Organization of the Early Church + and the Evolution of the Reader._ + + By the Rev. JOHN OWEN, Author of 'Evenings with the Skeptics.' + +'Dr. Adolf Harnack is at the present time undoubtedly the leading +liberal authority in Germany on matters connected with early Christian +history.'--_The Times._ + +'Those who are interested in early Church history know how to prize +anything from the pen of Prof. Harnack. They will not be disappointed +with the present paper, in which, with his accustomed learning and +acute criticism, he annotates and comments upon the fragments of +primitive church law which partly form the basis of the Apostolic +Canons.'--_British Weekly._ + +'The wide circulation of this volume would be of the happiest augury +for a more scientific and worthy conception of the organization of the +primitive Church.'--Dr. MARCUS DODS in _The Bookman_. + + + + _Crown 8vo., cloth, price 1s. 6d. net._ + + CHRISTIANITY AND HISTORY. + + By ADOLF HARNACK. + + Translated, with the Author's sanction, by THOMAS BAILEY + SAUNDERS, with an Introductory Note. + +'It is highly interesting and full of thought. The short introductory +note with which Mr. Saunders prefaces it is valuable for its +information and excellent in its tone.'--_Athenæum._ + +'A singularly able exposition and defence of Christianity, as seen in +the newer light, by one of the most learned and acute "evangelical" +critics of Germany. The essay is a masterly one.'--_Glasgow Herald._ + +' ... We hope the lecture will be widely read.'--_Primitive Methodist +Quarterly Review._ + +'The lecture itself is weighty in its every word, and should be read +and re-read by those desiring to have in a nutshell the central +positions of modern Christianity.'--_Christian World._ + + + LONDON: ADAM & CHARLES BLACK, SOHO SQUARE. + + + _Third Edition. Crown 8vo., cloth, price 5s._ + + SKETCH OF THE HISTORY OF + ISRAEL AND JUDAH. + + By J. WELLHAUSEN, + PROFESSOR AT MARBURG. + +'This work is now issued for the third time as an independent treatise. +It admirably epitomizes the subject, and exhibits on almost every page +evidences of Professor Wellhausen's profound study.'--_Publishers' +Circular._ + +'We would only say that those who differ from his critical views will +yet do well to study them, and to read this history in which he applies +them. Its separate publication, in a handy form and at a moderate +price, makes it generally accessible.'--_North British Daily Mail._ + +'The publication in a separate form of Professor Wellhausen's article +in the "Encyclopædia Britannica" on "Israel" will be very warmly +welcomed by many readers.'--_Manchester Guardian._ + +'We are very glad to welcome an edition of Professor Wellhausen's +"Sketch of the History of Israel and Judah" in a convenient and handy +form. This is the first time it has appeared in a separate form. It is +already known to students; it ought now to become popular. It is based +on the learned author's studies in Hebrew literature and history, and, +though not controversial in form, it differs totally from orthodox +presentations of the subject.'--_Westminster Review._ + +'A sketch which has created such widespread and profound interest as +this could not be kept in the pages of a voluminous encyclopædia. +Wellhausen's words necessarily have exceptional importance, even in +the esteem of those who differ from him _toto coelo_.'--_Baptist +Magazine._ + +'The profound scholarship of the author does not elevate his writing +above the interest of the general reader, and a vivid idea of the +involved Jewish history is obtainable from this volume.'--_Christian +Advocate._ + + + LONDON: ADAM & CHARLES BLACK, SOHO SQUARE. + + + _Demy 8vo., boards, price 3s. 6d. net._ + + A CLASSIFICATION OF + VERTEBRATA, + RECENT AND EXTINCT. + + With Diagnoses and Definitions, a Chapter on Geographical + Distribution, and an Etymological Index. + + By HANS GADOW, M.A., PH.D., F.R.S., + + STRICKLAND CURATOR AND LECTURER ON ZOOLOGY TO THE UNIVERSITY, + CAMBRIDGE. + +'At the end of his work Dr. Gadow adds a useful chapter on the +geographical distribution of the Vertebrata, with a table showing +the approximate number of the known recent species. He also gives +a fanciful though striking calculation to show how some groups are +still in the ascendant, while others are distinctly declining. The +little volume is indeed a welcome addition to the biological student's +library, and it deserves the wide circulation which its author's +eminence is likely to ensure for it.'--_Natural Science._ + +'It is a book, it need hardly be said, for the student; it is simply +a list of the principal sub-divisions of backboned animals, with just +as much definition as is needed. It may be regarded as an exceedingly +concentrated extract of a full text-book of the vertebrates.'--_Daily +Chronicle._ + + + + _Demy 8vo., cloth, price 21s._ + + IN NORTHERN SPAIN. + + By Dr. HANS GADOW, M.A., PH.D., F.R.S. + + _Containing Map and 89 Illustrations._ + +'Some years back "Wild Spain," one of the best books of its kind, +made you desirous of knowing more of the country. And Hans Gadow has +deepened this feeling in his excellent volume "In Northern Spain," +and that to an enormous extent. Dwelling at inn or farm, or in their +own tent, they saw the country as it has been seen but rarely, and +they came to know the inhabitants as they can be known in no other +fashion.'--_Black and White._ + +'To persons visiting the provinces with which the author deals, this +book will be invaluable, and will do more to point their attention to +objects of interest than existing guide-books of Spain, most of which +are out of date.'--_The Field._ + +'About the best book of European travel that has appeared these many +years.'--_Literary World._ + + + LONDON: ADAM & CHARLES BLACK, SOHO SQUARE. + + +Transcriber's Notes + + Variations in spelling, punctuation and hyphenation have been retained + except in obvious cases of typographical errors. + Inconsistent hyphenation and spelling are as in the oringinal. + Italics are shown thus _italic_ and underline thus *underline*. + + + + + +End of the Project Gutenberg EBook of The Last Link, by Ernst Haeckel + +*** END OF THE PROJECT GUTENBERG EBOOK 44541 *** diff --git a/44541-h/44541-h.htm b/44541-h/44541-h.htm new file mode 100644 index 0000000..924c8b3 --- /dev/null +++ b/44541-h/44541-h.htm @@ -0,0 +1,5195 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> + <head> + <meta http-equiv="Content-Type" content="text/html;charset=UTF-8" /> + <meta http-equiv="Content-Style-Type" content="text/css" /> + <title> + The Project Gutenberg eBook of The Last Link, by Ernst Haeckel. + </title> +<link rel="coverpage" href="images/cover.jpg" /> + <style type="text/css"> + +body { + margin-left: 10%; + margin-right: 10%; +} + +h1 +{ + margin-top: 2em; margin-bottom: 2em; + text-align: center; + font-size: x-large; + font-weight: normal; + line-height: 1.6; +} + h2,h3{ + text-align: center; /* all headings centered */ + clear: both; +} + +.spaced +{ + line-height: 1.5; +} + +.space-above +{ + margin-top: 3em; +} + +p +{ + margin-top: .75em; + text-align: justify; + margin-bottom: .75em; +} + + .small {font-size: small;} + .medium {font-size: medium;} + .large {font-size: large;} + +hr { + width: 33%; + margin-top: 2em; + margin-bottom: 2em; + margin-left: auto; + margin-right: auto; + clear: both; +} + +hr.tb {width: 45%;} +hr.chap {width: 65%} +hr.full {width: 95%;} + +table { + margin-left: auto; + margin-right: auto; +} + + .tdl {text-align: left;} + .tdr {text-align: right;} + .tdc {text-align: center;} + +.pagenum { /* uncomment the next line for invisible page numbers */ + visibility: hidden; + position: absolute; + left: 92%; + font-size: smaller; + text-align: right; +} /* page numbers */ + +.linenum { + position: absolute; + top: auto; + left: 4%; +} /* poetry number */ + +.blockquot { + margin-left: 5%; + margin-right: 10%; +} + +.center {text-align: center;} + +.right {text-align: right;} + +.smcap {font-variant: small-caps;} + +.u {text-decoration: underline;} + +@media handheld + +{.chapter-beginning + {page-break-before: always;} +} + +/* Images */ +.figcenter { + margin: auto; + text-align: center; +} + +/* Footnotes */ +.footnotes {border: dashed 1px;} + +.footnote {margin-left: 10%; margin-right: 10%; font-size: 0.9em;} + +.footnote .label {position: absolute; right: 84%; text-align: right;} + +.fnanchor { + vertical-align: super; + font-size: .8em; + text-decoration: + none; +} + +/* Transcriber's notes */ +.transnote {background-color: #E6E6FA; + color: black; + font-size:smaller; + padding:0.5em; + margin-bottom:5em; + font-family:sans-serif, serif; } + </style> + </head> +<body> +<div>*** START OF THE PROJECT GUTENBERG EBOOK 44541 ***</div> + +<h1>THE LAST LINK</h1> + +<p class="center">OUR PRESENT KNOWLEDGE OF THE + DESCENT OF MAN</p> + +<p class="center space-above"><small>BY</small><br /> +ERNST HAECKEL<br /> +<small>(JENA)</small></p> + +<p class="center space-above"><small>WITH NOTES AND BIOGRAPHICAL SKETCHES<br /> +BY</small><br /> +HANS GADOW, F.R.S.<br /> +<small>(CAMBRIDGE)</small></p> + + +<p class="center space-above">LONDON<br /> +ADAM AND CHARLES BLACK<br /> +1898</p> + +<hr class="chap"/> + +<h2>CONTENTS.</h2> + +<table id="toc" summary="contents"> +<tr> + <td> </td> + <td class="tdr"><span class="smcap">page</span></td> +</tr> +<tr> + <td class="tdl"><big>THE LAST LINK</big></td> + <td class="tdr"> </td> +</tr> +<tr> + <td class="tdl"> INTRODUCTORY</td> + <td class="tdr"><a href="#Page_1">1</a></td> +</tr> +<tr> + <td class="tdl"> COMPARATIVE ANATOMY</td> + <td class="tdr"><a href="#Page_8">8</a></td> +</tr> +<tr> + <td class="tdl"> PALÆONTOLOGY</td> + <td class="tdr"><a href="#Page_20">20</a></td> +</tr> +<tr> + <td class="tdl"> OTHER EVIDENCE</td> + <td class="tdr"><a href="#Page_42">42</a></td> +</tr> +<tr> + <td class="tdl"> STAGES RECAPITULATED</td> + <td class="tdr"><a href="#Page_47">47</a></td> +</tr> +<tr> + <td class="tdl"><big>BIOGRAPHICAL SKETCHES:</big></td> + <td class="tdr"> </td> +</tr> +<tr> + <td class="tdl"> LAMARCK, SAINT-HILAIRE, CUVIER, BAER,</td> + <td class="tdr"> </td> +</tr> +<tr> + <td class="tdl"> MUELLER, VIRCHOW, COPE, KOELLIKER, GEGENBAUR,</td> + <td class="tdr"> </td> +</tr> +<tr> + <td class="tdl"> HAECKEL</td> + <td class="tdr"><a href="#Page_80">80</a></td> +</tr> +<tr> + <td class="tdl">THEORY OF CELLS</td> + <td class="tdr"><a href="#Page_115">115</a></td> +</tr> +<tr> + <td class="tdl">FACTORS OF EVOLUTION</td> + <td class="tdr"><a href="#Page_117">117</a></td> +</tr> +<tr> + <td class="tdl">GEOLOGICAL TIME AND EVOLUTION</td> + <td class="tdr"><a href="#Page_135">135</a></td> +</tr> +</table> + +<hr class="chap" /> +<div class="chapter-beginning"/> + +<h2>NOTE</h2> + + +<p>The address I delivered on August 26 at the +Fourth International Congress of Zoology at +Cambridge, 'On our Present Knowledge of +the Descent of Man,' has, I find, from the +high significance of the theme and the +general importance of the questions connected +with it, excited much interest, and +has led to requests for its publication. +Hence this volume, edited by my friend +Dr. H. Gadow, my pupil in earlier days, +who has not only revised the text, but has +also enriched it by many valuable additions +and notes.</p> + +<p class="right">ERNST HAECKEL.</p> + +<p><small><i>Jena, December, 1898.</i></small></p> + +<p><span class="pagenum"><a name="Page_1" id="Page_1">[Pg 1]</a></span></p> + +<hr class="chap" /> +<div class="chapter-beginning"/> +<h2>THE LAST LINK</h2> + + +<p>At the end of the nineteenth century, the +age of 'natural science,' the department of +knowledge that has made most progress is +zoology. From zoology has arisen the study +of transformism, which now dominates the +whole of biology. Lamarck<a name="FNanchor_1_1" id="FNanchor_1_1"></a><a href="#Footnote_1_1" class="fnanchor">[1]</a> laid its foundation +in 1809, and forty years ago Charles +Darwin obtained for it a recognition which +is now universal. It is not my task to repeat +the well-known principles of Darwinism. I +am not concerned to explain the scientific +value of the whole theory of descent. The +whole of our biological study is pervaded by +it. No general problem in zoology and<span class="pagenum"><a name="Page_2" id="Page_2">[Pg 2]</a></span> +botany, in anatomy and physiology, can be +discussed without the question arising, How +has this problem originated? What are the +real causes of its development?</p> + +<p>This question was almost unknown seventy +years ago, when Charles Darwin, the great +reformer of biology, began his academical +career at Cambridge as a student of theology. +In the same year, 1828, Carl Ernst von +Baer<a name="FNanchor_2_2" id="FNanchor_2_2"></a><a href="#Footnote_2_2" class="fnanchor">[2]</a> published in Germany his classical +work on the embryology of animals, the first +successful attempt to elucidate by 'observation +and reflection' the mysterious origin +of the animal body from the egg, and to +explain in every respect the 'history of the +growing individuality.' Darwin at that time +had no knowledge of this great advance, and +he could not divine that forty years later +embryology would be one of the strongest +supports of his own life's work—of that very +theory of transformism which, founded by +Lamarck in the year of Darwin's birth,<span class="pagenum"><a name="Page_3" id="Page_3">[Pg 3]</a></span> +was accepted with enthusiasm by Charles's +grandfather Erasmus. There is no doubt +that of all the celebrated naturalists of the +nineteenth century Darwin achieved the +greatest success, and we should be justified +in designating the last forty years as the +Age of Darwin.</p> + +<p>In searching for the causes of this unexampled +success, we must clearly separate +three sets of considerations: first, the comprehensive +reform of Lamarck's transformism, +and its firm establishment by the many +arguments drawn from modern biology; +secondly, the construction of the new theory +of selection, as established by Darwin, and +independently by Alfred Wallace (a theory +called Darwinism in the proper sense); +thirdly, the deduction of anthropogeny, that +most important conclusion of the theory of +descent, the value of which far surpasses all +the other truths in evolution.</p> + +<p>It is the third point of Darwin's theory +that I shall discuss here; and I shall discuss<span class="pagenum"><a name="Page_4" id="Page_4">[Pg 4]</a></span> +it chiefly with the intention of examining +critically the evidence and the different +conclusions which at present represent our +scientific knowledge of the descent of man +and of the different stages of his animal +pedigree.</p> + +<p>It is now generally admitted that this +problem is the most important of all biological +questions. Huxley was right when +in 1863 he called it the question of questions +for mankind. The problem which underlies +all others, and is more deeply interesting than +any other, is as to the place which man +occupies in nature and his relations to the +universe of things. 'Whence our race has +come; what are the limits of our power over +nature, and of nature's power over us; to +what goal are we tending—these are the +problems which present themselves anew +and with undiminished interest to every man +born into the world.' This impressive view +was explained by Huxley thirty-five years ago +in his three celebrated essays on 'Evidence<span class="pagenum"><a name="Page_5" id="Page_5">[Pg 5]</a></span> +as to Man's Place in Nature.' The first is +entitled 'On the Natural History of the Man-like +Apes'; the second, 'On the Relations of +Man to the Lower Animals'; the third, 'On +some Fossil Remains of Man.' Darwin himself +felt the burden of these problems as much +as Huxley; but in his chief work, 'On the +Origin of Species,' in 1859, he had purposely +only just touched them, suggesting that the +theory of descent would shed light upon the +origin of man and his history. Twelve years +later, in his celebrated work on 'The Descent +of Man, and Selection in Relation to Sex,' +Darwin discussed fully and ingeniously all +the different sides of this 'question of +questions' from the morphological, historical, +physiological, and psychological points of +view. As early as 1866 I myself had applied +in the <i>Generelle Morphologie der Organismen</i> +the theory of transformism to anthropology, +and had shown that the fundamental law of +biogeny claims the same value for man as for +all the other animals. The intimate causal<span class="pagenum"><a name="Page_6" id="Page_6">[Pg 6]</a></span> +connection between ontogeny and phylogeny, +between the development of the individual and +the history of its ancestors, enables us to gain +a safe and certain knowledge of our ancestral +series. I had at that time distinguished in +this series ten chief degrees of vertebrate +organization. I attributed the highest importance +to the logical connection of anthropogeny +with transformism. If the latter be +true, the truth of the former is absolute. +'Our theory that man is descended from +lower vertebrates, and immediately from apes +or primates, is a case of special <i>deduction</i> +which follows with absolute certainty from the +general <i>induction</i> of the theory of descent.' +The full proof and detailed explanation of +this view was afterwards given in my +'History of Natural Creation,' and especially +in my 'Anthropogeny.'<a name="FNanchor_3_3" id="FNanchor_3_3"></a><a href="#Footnote_3_3" class="fnanchor">[3]</a> Lastly, it has +received an ample scientific and critical +foundation in the third part of my 'Systematic +Phylogeny.'<sup>[3]</sup></p> + +<p><span class="pagenum"><a name="Page_7" id="Page_7">[Pg 7]</a></span></p> +<p>During the forty years which have elapsed +since Darwin's first publication of his theories +an enormous literature, discussing the <i>general +problems</i> of transformism as well as its special +application to man, has been published. In +spite of the wide divergence of the different +views, all agree in one main point: the +natural development of man cannot be separated +from general transformism. There are +only two possibilities. Either all the various +species of animals and plants have been +created independently by supernatural forces +(and in this case the creation of man also is a +miracle); or the species have been produced +in a natural way by transmutation, by adaptation +and progressive heredity (and in this +case man also is descended from other vertebrates, +and immediately from a series of +primates). We are absolutely convinced that +only the latter theory is fully scientific. To +prove its truth, we have to examine critically +the strength of the different arguments claimed +for it.</p> + +<p><span class="pagenum"><a name="Page_8" id="Page_8">[Pg 8]</a></span></p> + +<hr class="chap"/> + +<h2>I.</h2> + + +<p>First, we have to consider the relative +place which comparative anatomy concedes +to man in the 'natural system' of animals, +for the true value of our 'natural classification' +is based upon its meaning as a pedigree. +All the minor and major groups of the system—the +classes, legions, orders, families, genera, +and species—are only different branches of +the same pedigree. For man himself, his +place in the pedigree has been fixed since +Lamarck,<a name="FNanchor_5_5" id="FNanchor_5_5"></a><a href="#Footnote_5_5" class="fnanchor">[5]</a> in 1801, defined the group of +vertebrates. The most perfect<a name="FNanchor_6_6" id="FNanchor_6_6"></a><a href="#Footnote_6_6" class="fnanchor">[6]</a> of these are<span class="pagenum"><a name="Page_9" id="Page_9">[Pg 9]</a></span> +the Mammalia; and at the head of this class +stands the order of Primates, in which Linnæus, +in 1735, united four 'genera'—Homo, +Simia, Lemur, and Vespertilio. If we exclude +the last-named, the Chiroptera of modern +zoology, there remain three natural groups of +Primates—the Lemures, the Simiæ, and the +Anthropi or Hominidæ. This is the classification<span class="pagenum"><a name="Page_10" id="Page_10">[Pg 10]</a></span> +of the majority of zoologists; but if we +compare man with the two chief groups of +monkeys—the Eastern monkeys (or Catarrhinæ) +and the Western or American monkeys +(Platyrrhinæ)—there can be no doubt that the +former group is much more closely related to +man than is the latter. In the natural order +of the Catarrhinæ we find united a long series +of lower and higher forms. The lowest, the +Cynopitheci, appear still closely related to +the Platyrrhinæ and to the Lemures; while, +on the other hand, the tailless apes (Anthropomorphæ) +approach man through their +higher organization. Hence one of our best +authorities on the Primates, Robert Hartmann,<a name="FNanchor_7_7" id="FNanchor_7_7"></a><a href="#Footnote_7_7" class="fnanchor">[7]</a> +proposed to subdivide the whole +order of the Simiæ into three groups:</p> + +<p>(1) Primarii, man together with the other +Anthropomorphæ, or tailless apes; (2) +Simiæ, all the other monkeys; (3) Prosimiæ, +or Lemurs. This arrangement has received<span class="pagenum"><a name="Page_11" id="Page_11">[Pg 11]</a></span> +strong support from the interesting discovery +by Selenka that the peculiar placentation of +the human embryo is the same as in the +great apes, and different from that of all the +other monkeys. Our choice between these +different classifications of Primates is best +determined by the important thesis of Huxley, +in which, in 1863, he carried out a most careful +and critical comparison of all the anatomical +gradations within this order. In my opinion, +this ingenious thesis—which I have called the +Huxleyan Law, or the 'Pithecometra-thesis +of Huxley'—is of the utmost value. It runs +as follows: 'Thus, whatever system of +organs be studied, the comparison of their +modifications in the ape-series leads to one +and the same result—that the structural +differences which separate man from the +gorilla and the chimpanzee are not so great +as those which separate the gorilla from the +lower apes.' If we accept the Huxleyan +law without prejudice, and apply it to the +natural classification of the Primates, we<span class="pagenum"><a name="Page_12" id="Page_12">[Pg 12]</a></span> +must concede that man's place is within the +order of the Simiæ. On examining this +relation with care, and judging with logical +persistence, we may even go a step further. +Instead of the wider conception of 'Simiæ,' +we must use the restricted term of Catarrhinæ, +and our Pithecometra-thesis has then +to be formulated as follows: <i>The comparative +anatomy of all organs of the group of Catarrhine +Simiæ leads to the result that the +morphological differences between man and +the great apes are not so great as are those +between the man-like apes and the lowest +Catarrhinæ</i>. In fact, it is very difficult to +show why man should not be classed with +the large apes in the same zoological family. +We all know a man from an ape; but it is +quite another thing to find differences which +are absolute and not of degree only. Speaking +generally, we may say that man alone +combines the four following features: (1) +Erect walk; (2) extremities differentiated +accordingly; (3) articulate speech; (4) higher<span class="pagenum"><a name="Page_13" id="Page_13">[Pg 13]</a></span> +reasoning power. Speech and reason are +obviously relative distinctions only—the direct +result of more brains and more brain-power, +the so-called mental faculties. The erect walk +is not an absolutely distinguishing characteristic: +the large apes likewise walk on their +feet only, supporting their bodies by touching +the ground with the backs of their hands—in +fact, with their knuckles—and this is a mode +of progression very different from that of the +tailed monkeys, which walk upon the palms +of their hands. There are, however, two +obvious differences in the development of +the muscles. In man alone the gastrocnemius +and the soleus muscle are thick +enough to form the calf of the leg, and +the glutæus maximus is enlarged into the +buttocks. A fourth glutæal muscle occurs +occasionally in man, while it is constantly +present in apes as the so-called musculus +scansorius. Concerning the muscles of the +whole body, we cannot do better than quote +Testut's summary: 'The mass of recorded<span class="pagenum"><a name="Page_14" id="Page_14">[Pg 14]</a></span> +observations upon the muscular anomalies in +man is so great, and the agreement of many +of these with the condition normal in apes is so +marked, that the gap which usually separates +the muscular system of man from that of the +apes appears to be completely bridged over.'</p> + +<p>There are, for example, the muscles of the +ear. In most people the majority, or even +all of them, are no longer movable at will, +while in the apes they are still in use. The +important point, however, is that these +muscles are still present in man, although +often in a reduced condition. They are the +following: (1) Musculus auricularis anterior +or attrahens auris, which is frequently much +reduced and no longer reaches the ear at all, +being then absolutely useless; (2) Musculus +auricularis superior or attollens auris, more +constant than the former; (3) Musculus +auricularis posterior or retrahens auris, likewise +often functional. Occasionally smaller +slips differentiated from these three muscles +are present, and as so-called intrinsic muscles<span class="pagenum"><a name="Page_15" id="Page_15">[Pg 15]</a><br /><a name="Page_16" id="Page_16">[Pg 16]</a></span> +are restricted to the ear itself; their function +is, or was, that of curling up or opening the +external ear.</p> + +<div class="figcenter"><a href="./images/i_0231.jpg"> + <img src="./images/i_0231.jpg" alt="Outlines of the Left Ear"></img></a> +</div> +<p class="center"><span class="smcap">Outlines of the Left Ear of—</span></p> + +<blockquote> +<p><small>1. <i>Lemur macaco</i>; 2. <i>Macacus rhesus</i>, the Rhesus monkey; +3. Cercopithecus, a macaque; 4. human embryo of six months; +5. man, with Darwin's point well retained: the dotted outline is that +of the ear of a baboon; 6. orang-utan (after G. Schwalbe):<a name="FNanchor_8_8" id="FNanchor_8_8"></a><a href="#Footnote_8_8" class="fnanchor">[8]</a> <sup>x</sup> the +original tip of the ear; 7. human ear with the principal muscles.</small></p> +</blockquote> + +<p>In connection with the ear, I may touch +upon another interesting and most suggestive +little feature which is present in many +individuals—namely, 'Darwin's point.' This +is the last remnant of the original tip of the +ear, before the outer, upper, and hinder rim +became doubled up or folded in. It is a +feature quite useless, and absolutely impossible +of interpretation, excepting as the vestige of +such previous ancestral conditions as are +normal in the monkeys.</p> + +<p>In some cases the reduction of muscles +has proceeded further in apes than in man—for +example, the muscles of the little toe. +Another instance is afforded by the coccyx or +vestige of the tail; this is still furnished with +muscles which are now in man, as well as in +the apes, quite useless, and vary considerably +with every sign of degeneration, most so in +the orang-utan.</p> + +<p><span class="pagenum"><a name="Page_17" id="Page_17">[Pg 17]</a></span></p> + +<p>Darwin has mentioned the frequent action +of the 'snarling muscle,' by which, in sneering, +our upper canine teeth are exposed, like those +of a dog prepared to fight.</p> + +<p>Monkeys and apes possess vocal sacs, +especially large in the orang-utan; survivals +of them, although no longer used, persist in +man in the shape of a pair of small diverticula, +the pouches of Morgagni, between the +true and the false vocal cords.</p> + +<p>'In the native Australians, the dental formula +appears least removed from the hypothetical +original type, for in it are still found +complete rows of splendid teeth, with powerfully-developed +canines and molars, the latter +being either uniform, or even increasing in +size, as we proceed backwards, in such a +way that the wisdom tooth is the largest of +the series. This is decidedly a pithecoid +characteristic which is always found in apes. +The upper incisors of the Malay, apart from +their prognathous disposition, have occasionally +a distinctly pithecoid form, their anterior<span class="pagenum"><a name="Page_18" id="Page_18">[Pg 18]</a></span> +surface being convex, and their lingual surface +slightly concave. The ancestors of +Europeans seem to have had the same form +of teeth, for the oldest existing fragments of +skulls from the Mammoth age (<i>e.g.</i>, the jaws +from La Naulette, in Belgium) reveal tooth-forms +which must be classed with those of +the lowest races of to-day.'<a name="FNanchor_9_9" id="FNanchor_9_9"></a><a href="#Footnote_9_9" class="fnanchor">[9]</a></p> + +<p>Now we are able to apply this fundamental +Pithecometra-thesis directly to the classification +of the Primates and to the phylogeny of +man, which is intimately connected with it, +because in this order, as in all the other +groups of animals, the natural system is the +clear expression of true phylogenetic affinity. +Four results follow from our thesis: (1) The +Primates, as the highest legion or order of +mammals, form one natural, monophyletic +group. All the Lemures, Simiæ, and +Homines descend from one common ancestral<span class="pagenum"><a name="Page_19" id="Page_19">[Pg 19]</a></span> +form, from a hypothetical 'Archiprimas.' +(2) The Lemures are the older and +lower of the natural groups of the Primates; +they stand between the oldest Placentalia +(Prochoriata) and the true Simiæ. (3) All +the Catarrhinæ, or Eastern Simiæ, form one +natural monophyletic group. Their hypothetical +common ancestor, the Archipithecus, +may have descended directly or indirectly +from a branch of the Lemures. (4) Man +is descended directly from one series of +extinct Catarrhine ancestors. The more +recent ancestors of this series were tailless +anthropoids (similar to the Anthropopithecus), +with five sacral vertebræ. The +more remote ancestors were tailed Cercopitheci, +with three or four sacral vertebræ.</p> + +<p>These four theses possess, in my opinion, +absolute certainty. They are independent of +all future anatomical, embryological, and +palæontological discoveries which may possibly +throw more light upon the details of +our phyletic anthropogenesis.</p> + +<p><span class="pagenum"><a name="Page_20" id="Page_20">[Pg 20]</a></span></p> + +<hr class="chap"/> +<div class="chapter-beginning"/> +<h2>II.</h2> + + +<p>The next question is, how the facts of +palæontology agree with these most important +results of comparative anatomy and ontogeny. +The fossils are the true historical 'medals of +creation,' the palpable evidence of the historical +succession of all those innumerable +organic forms which have peopled the globe +for many millions of years. Here the question +arises, If the known fossil specimens of Mammalia, +and particularly of Primates, give proof +of these Pithecometra-theses, do they confirm +directly the descent of man from ape-like +creatures? The answer to this question +is, in my opinion, affirmative.</p> + +<p>It is true that the gaps in the palæontological +evidence, here as elsewhere, are<span class="pagenum"><a name="Page_21" id="Page_21">[Pg 21]</a></span> +many and keenly felt. In the order of the +Primates they are greater than in many +other orders, chiefly because of the arboreal +life of our ancestors. The explanation is very +simple. It is really due to a long chain of +favourable coincidences if the skeleton of a +vertebrate, covered as it was with flesh and +skin, and containing still more perishable +viscera, is petrified at all. The body may be +devoured by other creatures, and its bones +scattered about; or it rots away and crumbles +to pieces. Many animals hide in thick undergrowth +when death approaches them; and, +leading an almost entirely arboreal life, the +Primates are especially likely to disappear +without being fossilized. It is only when the +body is quickly covered with sand, or is embedded +in suitable lime or silica containing +mud, that the process of petrifaction can +come to pass. Even then it is only by great +good luck that we come across such a fossil. +Very few countries have been searched +systematically, and the areas that have been<span class="pagenum"><a name="Page_22" id="Page_22">[Pg 22]</a></span> +searched amount to little in comparison with +the whole surface of the land, even if we +leave out of account the fact that more than +two-thirds of the globe are covered by water.</p> + +<p>These deplorable deficiencies of empirical +palæontology are balanced on the other side +by a growing number of positive facts, which +possess an inestimable value in human +phylogeny. The most interesting and most +important of these is the celebrated fossil +<i>Pithecanthropus erectus</i>, discovered in Java +in 1894 by Dr. Eugène Dubois.<a name="FNanchor_10_10" id="FNanchor_10_10"></a><a href="#Footnote_10_10" class="fnanchor">[10]</a> Three +years ago this now famous ape-like man +provoked an animated discussion at the third +International Zoological Congress at Leyden. +I may therefore be allowed to say a few +words as to its scientific significance. Unfortunately, +the fossil remains of this creature +are very scanty: the skull-cap, a femur, and +two teeth. It is obviously impossible to form<span class="pagenum"><a name="Page_23" id="Page_23">[Pg 23]</a></span> +from these scanty remains a complete and +satisfactory reconstruction of this remarkable +Pliocene Primate.</p> + +<p>The more important points are the following: +The remains in question rested upon a +conglomerate which lies upon a bed of marine +marl and sand of Pliocene age. Together +with the bones of Pithecanthropus were found +those of Stegodon, Leptobos, Rhinoceros, Sus, +Felis, Hyæna, Hippopotamus, Tapir, Elephas, +and a gigantic Pangolin. It is remarkable +that the first two of these genera are now +extinct, and that neither hippopotamus nor +hyæna exists any longer in the Oriental region. +If we may judge from these fossil remains, +the bones of Pithecanthropus are not younger +than the oldest Pleistocene, and probably +belong to the upper Pliocene. The teeth +are like those of man. The femur, also, is +very human, but shows some resemblances +to that of the gibbons. Its size, however, +indicates an animal which stood when erect +not less than 5 feet 6 inches high. The<span class="pagenum"><a name="Page_24" id="Page_24">[Pg 24]</a></span> +skull-cap also is very human, but with very +prominent eyebrow ridges, like those of +the famous Neanderthal cranium. It is +certainly not that of an idiot. It had an +estimated cranial capacity of about 1,000 +cubic centimetres—that is to say, much +more than that of the largest ape, which +possesses not more than 600 c.c. The crania +of female Australians and Veddahs measure +not more than 1,100, some even less than +1,000 c.c.; but, as these Veddah women stand +only about 4 feet 9 inches high, the computed +cranial capacity of the much taller Pithecanthropus +is comparatively very low indeed.<a name="FNanchor_11_11" id="FNanchor_11_11"></a><a href="#Footnote_11_11" class="fnanchor">[11]</a></p> + +<div class="figcenter"><a href="./images/i_0331.jpg"> + <img src="./images/i_0331.jpg" alt="Skulls"></img></a> +</div> + +<blockquote> +<p><small>The upper figure represents the outlines of the skull of Pithecanthropus, +as restored by Manouvier.<a name="FNanchor_12_12" id="FNanchor_12_12"></a><a href="#Footnote_12_12" class="fnanchor">[12]</a> The lower figure shows the +comparative size and shape of Pithecanthropus, the Neanderthal +skull, a specimen of the Cro-Magnon race of neolithic France, and a +Young Chimpanzee before the full development of the supraorbital +crests</small>.</p> +</blockquote> + +<p>The final result of the long discussion at +Leyden was that, of twelve experts present, +three held that the fossil remains belonged +to a low race of man; three declared them +to be those of a man-like ape of great size;<span class="pagenum"><a name="Page_25" id="Page_25">[Pg 25]</a><br /><a name="Page_26" id="Page_26">[Pg 26]</a></span> +the rest maintained that they belonged to an +intermediate form, which directly connected +primitive man with the anthropoid apes. +This last view is the right one, and accords +with the laws of logical inference. <i>Pithecanthropus +erectus</i> of Dubois is truly a +Pliocene remainder of that famous group of +highest Catarrhines which were the immediate +pithecoid ancestors of man. He is, indeed, the +long-searched-for 'missing link,' for which, in +1866, I myself had proposed the hypothetical +genus Pithecanthropus, species Alalus.</p> + +<p>It must, however, be admitted that this +opinion is still strongly combated by some +distinguished authorities. At the Leyden +Congress it was attacked by the illustrious +pathologist Rudolf Virchow.<a name="FNanchor_13_13" id="FNanchor_13_13"></a><a href="#Footnote_13_13" class="fnanchor">[13]</a> He, however, +is one of the minority of leading men of +science who set themselves to refute the +theory of Evolution in every possible way. +For thirty years he has defended the thesis: +'It is quite certain that man is not a<span class="pagenum"><a name="Page_27" id="Page_27">[Pg 27]</a></span> +descendant of apes.' He declares any intermediate +form to be unimaginable save in a +dream.</p> + +<p>Virchow went to the Leyden Congress +with the set purpose of disproving that the +bones found by Dubois belonged to a creature +which linked together apes and man. First, +he maintained that the skull was that of an +ape, while the thigh belonged to man. This +insinuation was at once refuted by the expert +palæontologists, who declared that without +the slightest doubt the bones belonged to +one and the same individual. Next, Virchow +explained that certain exostoses or growths +observable on the thigh proved its human +nature, since only under careful treatment +the patient could have healed the original +injury. Thereupon Professor Marsh, the +celebrated palæontologist, exhibited a number +of thigh-bones of wild monkeys which +showed similar exostoses and had healed +without hospital treatment. As a last argument +the Berlin pathologist declared that<span class="pagenum"><a name="Page_28" id="Page_28">[Pg 28]</a></span> +the deep constriction behind the upper +margin of the orbits proved that the skull +was that of an ape, as such never occurred in +man. It so happened that a few weeks later +Professor Nehring of Berlin demonstrated +exactly the same formation on a human prehistoric +skull received by him from Santos, +in Brazil.</p> + +<p>Virchow was, in fact, just as unlucky in +Leyden in his fight with our pliocene +ancestor as he had been unfortunate in his +opinion on the famous skulls of Neanderthal, +Spy, La Naulette, etc., every one of which he +explained as a pathological abnormality. It +would be a very curious coincidence indeed if +all these and other fossil human remains +were those of idiots or otherwise abnormal +individuals, provided they are old and low +enough in their organization to be of phylogenetic +value to the unbiassed zoologist.</p> + +<p>As the sworn adversary of Evolution, +transformism, and Darwinism in particular, +but a believer in the constancy of species, the<span class="pagenum"><a name="Page_29" id="Page_29">[Pg 29]</a></span> +great and renowned pathologist has been +driven to the incredible contention that all +variations of organic forms are pathological.</p> + +<p>Four years ago, as honorary president of +the Anthropological Congress at Vienna, he +attacked Darwinism in the severest manner, +and declared that 'man may be as well +descended from the elephant or from the +sheep as from the ape.' Such attacks on the +theory of transformism indicate a failure to +understand the principles of the theory of +Evolution and to appreciate the significance +of palæontology, comparative anatomy, and +ontogeny.</p> + +<p>The thousands of other objections which +have been made during the last forty years +(chiefly by outsiders) may be passed over in +silence. They do not require serious refutation. +In spite of, or perhaps because of, +these attacks, the theory of Evolution stands +established more firmly than ever.</p> + +<p>It is easy for the outsider to exult over the +difficulties which our problem implies—diffi<span class="pagenum"><a name="Page_30" id="Page_30">[Pg 30]</a></span>culties +which we who have given our lives to +the study understand likewise, and try our +best not only to bridge over, but also to +point out. Anyhow, we do not conceal +them; while those who reject the explanation +offered by Evolution make the most of the +gaps, and pass silently over the far more +numerous points favourable to our theory.</p> + +<p>How fruitful during the last thirty years +the astonishing progress in our palæontological +knowledge has been for our Pithecometra-thesis +is best shown by a short glance +at the growth of our knowledge of fossil +Primates. Cuvier,<a name="FNanchor_14_14" id="FNanchor_14_14"></a><a href="#Footnote_14_14" class="fnanchor">[14]</a> the founder of palæontology, +continued up to the time of his death, +in 1832, to assert that fossil remains of +monkeys and lemurs did not exist. The +only skull of a fossil lemuroid which he described +(namely, Adapis) he declared to be +that of an ungulate. Not until 1836 were +the first fragments of extinct monkeys found +in India; it was two years later, near Athens,<span class="pagenum"><a name="Page_31" id="Page_31">[Pg 31]</a></span> +that the skeleton of <i>Mesopithecus penthelicus</i> +was discovered. Other remains of lemurs +were found in 1862. But during the last +twenty years the number of fossil Primates +has been augmented by the remarkable discoveries +of Gaudry, Filhol, Milne Edwards, +Seeley, Schlosser, and others in Europe; of +Marsh, Cope, Osborn, Leidy, Ameghino, in +South America; and Forsyth Major in +Madagascar.<a name="FNanchor_15_15" id="FNanchor_15_15"></a><a href="#Footnote_15_15" class="fnanchor">[15]</a> These tertiary remains, chiefly<span class="pagenum"><a name="Page_32" id="Page_32">[Pg 32]</a></span> +of Eocene and Miocene date, fill many gaps +between existing genera of Primates, and +afford us quite a clear insight into the phyletic +development of this order during the +millions of years of the Cænozoic age.</p> + +<p>The most important difference between the +two groups of existing monkeys is indicated +by their dentition. Adult man possesses, +like all the other Catarrhine Simiæ, thirty-two +teeth, whilst the American monkeys (the +Platyrrhinæ) have thirty-six teeth—namely, +one pair of premolars more in the upper and +lower jaws. Comparative odontology leads +us to the phylogenetic conclusion that this +number has been produced by reduction from +a still older form with forty-four teeth. This +typical dental formula (three incisors, one +canine, four premolars, and three molars, in +each half-jaw) is common to all those most +important older mammals which in the beginning +of the Eocene period constituted the four +large groups of Lemuravida, Condylarthra, +Esthonychida, and Ictopsida. These are the<span class="pagenum"><a name="Page_33" id="Page_33">[Pg 33]</a></span> +four ancestral groups of the four main orders +of Placentalia—namely, of the Primates, +Ungulata, Rodentia, and Carnassia. They +seem to be so closely related by their primitive +organization that they may be united in +one common super-order, Prochoriata.</p> + +<p>With a considerable degree of probability, +we are led to formulate the further +hypothesis that all the orders of Placentalia—from +the lowest Prochoriata upwards to +man—have descended from some unknown +common ancestor living in the Cretaceous +period, and that this oldest placental form +originated from some Jurassic group of +marsupials.</p> + +<p>Among these numerous fossil Lemures +which have been discovered within the last +twenty years, there exist, indeed, all the connecting +forms of the older series of Primates, +all the 'missing links' sought for by comparative +odontology.</p> + +<p>The oldest Lemures of the tertiary age +are the Eocene Pachylemures, or Hyopso<span class="pagenum"><a name="Page_34" id="Page_34">[Pg 34]</a></span>dina. +They possess the complete dentition +of the Prochoriata—namely, forty-four teeth +(3.1.4.3/3.1.4.3). Then follow the Eocene Palæolemures, +or Adapida, with forty teeth, they +having lost one pair of incisors in each jaw. +To these are attached the younger Autolemures, +or Stenopida, with thirty-six teeth, +they thus possessing already the same dentition +as the Platyrrhinæ. The characteristic +dentition of the Catarrhinæ is derived from +this formula by the loss of another premolar.</p> + +<p>These relations are so clear and so closely +connected with a gradual transformation of +the whole skull, and with the progressive +differentiation of the Primate-form, that we +are justified in saying that the pedigree of the +Primates, from the oldest Eocene Lemures +upwards to man, is now so well known, its +principal features so firmly fixed within the +Tertiary age, that there is no missing link +whatever.</p> + +<p>Quite different, and much more incom<span class="pagenum"><a name="Page_35" id="Page_35">[Pg 35]</a></span>plete, +is the palæontological evidence, if we +go further back into the Secondary or Mesozoic +age, and look there for the older ancestors +of the mammalian series. There we +meet everywhere with wide gaps, and the +scarce fragments of fossil Mesozoic mammals +(excessively rare in the Cretaceous formation) +are too poor to permit definite conclusions as +to their systematic position. Indeed, comparative +anatomy and ontogeny lead us to the +hypothesis that the oldest Cretaceous Mammalia—the +Prochoriata—are descended from +Jurassic marsupials, and these again from +Monotremes. We may also suppose with +high probability that among the unknown +Cretaceous Prochoriata there have been +Lemuravida and forms intermediate between +these and the Jurassic Amphitheriidæ, and +that these marsupials in their turn are descendants +of Pantotheria or similar monotreme-like +creatures of the Triassic age. Any +certain evidence for these hypotheses is at +present still wanting. One important fact,<span class="pagenum"><a name="Page_36" id="Page_36">[Pg 36]</a></span> +however, is established—namely, that these +interesting and oldest Mammalia—the Pantotheria +of Marsh, the Triassic Dromatheriidæ, +and the Jurassic Triconodontidæ of Osborn—were +small insectivorous mammals with a very +primitive organization. Probably they were +Monotremes, and may be derived directly +from Permian Sauromammalia, an ill-defined +mixture of Mammalia and Reptilia.</p> + +<p>This generalized characteristic supports +our view that <i>the whole class of Mammalia is +monophyletic</i>, and that all its members, from +the oldest Monotremes upwards to man, have +descended from one common ancestor living +in the older Triassic, or perhaps in the +Permian, age. To acquire full conviction of +this important conception, we have only to +think of the hair and the glands of our +human skin, of our diaphragm, the heart and +the blood corpuscles without a nucleus, our +skull with its squamoso-mandibular articulation. +All these singular and striking modifications +of the vertebrate organization are<span class="pagenum"><a name="Page_37" id="Page_37">[Pg 37]</a></span> +common to mammals, and distinguish them +clearly from the other Craniota. This characteristic +combination and correlation proves +that they have been developed only <i>once</i> in +the history of the vertebrate stem, and that +they have been transferred by heredity from +one common ancestor to all the members of +the class of Mammalia.</p> + +<p>The next step, as we trace our human +phylogeny to its origin, leads us further back +into the lower Vertebrata, into that obscure +Palæozoic age the immeasurable length of +which (much greater than that of the +Mesozoic) may, according to one of the +newest geological calculations, have comprised +about one thousand millions of years.<a name="FNanchor_16_16" id="FNanchor_16_16"></a><a href="#Footnote_16_16" class="fnanchor">[16]</a></p> + +<p>The first important fact we have to face +here is the complete absence of mammalian +remains. Instead of these we find in the +later Palæozoic period, the Permian, air-breathing +<i>reptiles</i> as the earliest representatives +of Amniota. They belong to the<span class="pagenum"><a name="Page_38" id="Page_38">[Pg 38]</a></span> +most primitive order of that class, the +Tocosauria; and besides them there were +the Theromorpha, which approach the Mammalia +in a remarkable manner. These +reptiles in turn were preceded, in the Carboniferous +period, by true Amphibia, most +of them belonging to the armour-clad +Stegocephali. These interesting Progonamphibia +were the oldest Tetrapoda, the first +vertebrates which had adapted themselves +to the terrestrial mode of life; in them the +swimming fin of fishes and Dipneusta was +transformed into the pentadactyle extremities +characteristic of quadrupeds.</p> + +<p>To appreciate the high importance of this +metamorphosis, we need only compare the +skeleton of our own human limbs with that +of the living Amphibia. We find in the +latter the same characteristic composition +as in man: the same shoulder and pelvic +girdle; the same single bone, the humerus +or the femur, followed by the same pair of +bones in the forearm and leg; then the same<span class="pagenum"><a name="Page_39" id="Page_39">[Pg 39]</a></span> +skeletal elements composing the wrist and +the ankle regions; and, lastly, the same five +fingers and toes.</p> + +<p>The arrangement of these bones, peculiar +and often complicated, but everywhere +essentially the same in all the Tetrapoda, +is a striking evidence that man is a +descendant from the oldest pentadactyle +Amphibia of the Carboniferous period. In +man the pentadactyle type has been better +preserved by constant heredity than in many +other Mammalia, notably the Ungulata.</p> + +<p>The oldest Carboniferous Amphibia, the +armour-clad Stegocephali, and especially the +remarkable Branchiosauri discovered by +Credner, are now regarded by all competent +zoologists as the indubitable common ancestral +group of all Tetrapoda, comprising both +Amphibia and Amniota. But whence this +most remote group of Tetrapoda? That +difficult question is answered by the marvellous +progress of modern palæontology, and +the answer is in complete harmony with<span class="pagenum"><a name="Page_40" id="Page_40">[Pg 40]</a></span> +the older results arrived at by comparative +anatomy and ontogeny. Thirty-four years +ago Carl Gegenbaur,<a name="FNanchor_17_17" id="FNanchor_17_17"></a><a href="#Footnote_17_17" class="fnanchor">[17]</a> the great living master +of comparative anatomy, had demonstrated +in a series of works how the skeletal +parts of the various classes of Vertebrata, +especially the skull and the limbs, still represent +a continuous scale of phyletic gradations. +Apart from the Cyclostomes, there are the +fishes, and among them the Elasmobranchi +(sharks and rays), which have best preserved +the original structure in all its essential parts +of organization. Closely connected with the +Elasmobranchi are the Crossopterygii, and +with these the Dipneusta or Dipnoi. Among +the latter the highest importance attaches +to the ancient Australian Ceratodus. Its +organization and development is now, at +last, becoming well known. This transitional +group of Dipnoi, 'fishes with lungs' +but without pentadactyle limbs, is the +morphological bridge which joins the<span class="pagenum"><a name="Page_41" id="Page_41">[Pg 41]</a></span> +Ganoids and the oldest Amphibia. With +this chain of successive groups of Vertebrata, +constructed anatomically, the palæontological +facts agree most satisfactorily. +Selachians and Ganoids existed in the +Silurian times, Dipnoi in the Devonian, +Amphibia in the Carboniferous, Reptilia in +the Permian, Mammalia in the Trias. These +are historical facts of first rank. They +connote in the most convincing manner that +remarkable ascending scale in the series of +vertebrates for our knowledge of which we +are indebted to the works of Cuvier and +Blainville, Meckel, Johannes Mueller and +Gegenbaur, Owen and Huxley. The historical +succession of the classes and orders +of the Vertebrata in the course of untold +millions of years is definitely fixed by the +concordance of those leading works, and this +invaluable acquisition is much more important +for the foundation of our human +pedigree than would be a complete series of +all possible skeletons of Primates.</p> + +<p><span class="pagenum"><a name="Page_42" id="Page_42">[Pg 42]</a></span></p> + +<p>Greater and more frequent difficulties +arise if we penetrate further into the most +remote part of the human phylogeny, and +attempt to derive the vertebrate stem from +an older stem of invertebrate ancestors. +None of those had a skeleton which could be +petrified; and the same remark applies to +the lowest classes of Vertebrata—to the +Cyclostomes and the Acrania. Palæontology, +therefore, can tell us nothing about them; +and we are limited to the other two great +documents of phylogeny—the results of comparative +anatomy and ontogeny. The value +of their evidence is, however, so great that +every competent zoologist can perceive the +most important features of the most remote +portion of our phylogeny.</p> + +<p>Here the first place belongs to the invaluable +results which modern comparative +ontogeny has gained by the aid of the +biogenetic law or the theory of recapitulation. +The foundation-stones of vertebrate embryology +had been laid by the works of Von<span class="pagenum"><a name="Page_43" id="Page_43">[Pg 43]</a></span> +Baer, Bischoff,<a name="FNanchor_18_18" id="FNanchor_18_18"></a><a href="#Footnote_18_18" class="fnanchor">[18]</a> Remak, and Koelliker;<a name="FNanchor_19_19" id="FNanchor_19_19"></a><a href="#Footnote_19_19" class="fnanchor">[19]</a> but +the clearest light was thrown upon it by the +famous discoveries of Kowalevsky<a name="FNanchor_20_20" id="FNanchor_20_20"></a><a href="#Footnote_20_20" class="fnanchor">[20]</a> in 1866. +He proved the identity of the first developmental +stages of Amphioxus and +the Ascidians, and thereby confirmed the +divination of Goodsir, who had already +announced the close affinity of Vertebrates +and Tunicates. The acknowledgment of +this affinity has proved of increasing importance, +and has abolished the erroneous +hypothesis that the Vertebrata may have +arisen from Annelids or from other Articulata. +Meanwhile, from 1860 to 1872, I +myself had been studying the development +of the Spongiæ, Medusæ, Siphonophora, and +other Cœlenterata. Their comparison led +me to the statements embodied in the<span class="pagenum"><a name="Page_44" id="Page_44">[Pg 44]</a></span> +'Gastræatheorie,' the first abstract of which +was published in 1872 in my monograph of +the Calcispongiæ.</p> + +<p>These ideas were carried on and expanded +during the subsequent ten years by +the help of many excellent embryologists—first +of all by E. Ray Lankester and Francis +Balfour. The most fruitful result of these +widely extended researches was the conclusion +that the first stages of embryonic +development are essentially the same in all +the different Metazoa, and that we may +derive from these facts certain views on the +common descent of all from one ancestral +form. The unicellular egg<a name="FNanchor_21_21" id="FNanchor_21_21"></a><a href="#Footnote_21_21" class="fnanchor">[21]</a> repeats the stage +of our Protozoan ancestors; the Blastula is +equivalent to an ancestral cœnobium of +Magosphæra or Volvox; the Gastrula is +the hereditary repetition of the Gastræa, the +common ancestor of all the Metazoa.</p> + +<p>Man agrees in all these respects with the +other vertebrates, and must have descended +with them from the same common root.</p> + +<p><span class="pagenum"><a name="Page_45" id="Page_45">[Pg 45]</a></span></p> + +<p>Particularly obscure is that part of our +phylogeny which extends from the Gastræa +to Amphioxus. The morphological importance +of this last small creature had been +perceived by Johannes Mueller, who in 1842 +gave the first accurate description of it. It +would not, of course, be correct to proclaim +the modern Amphioxus the common ancestor +of all the vertebrates; but he must be regarded +as closely related to them, and as the only +survivor of the whole class of Acrania. If +the Amphioxidæ had through some unfortunate +accident become extinct, we should +not have been able to gain anything like a +positive glimpse at our most remote vertebrate +ancestor. On the one hand, Amphioxus is +closely connected with the early larva of the +Cyclostomes, which are the oldest Craniota, +and the pre-Silurian ancestors of the fishes. +On the other hand, the ontogeny of Amphioxus +is in harmony with that of the Ascidians, +and if this agreement is not merely coincidental, +but due to relationship, we are +justified in reconstructing for both Ascidians<span class="pagenum"><a name="Page_46" id="Page_46">[Pg 46]</a></span> +and Amphioxus one common ancestral group +of chordate animals, the hypothetical <i>Prochordonia</i>. +The modern Copelata give us +a remote idea of their structure. The curious +Balanoglossus, the only living form of Enteropneusta, +seems to connect these Prochordonia +with the Nemertina and other Vermalia, +which we unite in one large class—Frontonia.</p> + +<p>No doubt these pre-Cambrian Vermalia, +and the common root of all Metazoa, the +Gastræades, were connected during the +Laurentian period by a long chain of intermediate +forms, and probably among these +were some older forms of Rotatoria and +Turbellaria; but at present it is not possible +to fill this wide gap with hypotheses that +are satisfactory, and we have to admit that +here indeed are many missing links in the +older history of the Invertebrata. Still, +every zoologist who is convinced of the truth +of transformism, and is accustomed to phylogenetic +speculations, knows very well that +their results are most unequal, often incomplete.</p> + +<p><span class="pagenum"><a name="Page_47" id="Page_47">[Pg 47]</a></span></p> + +<hr class="chap"/> +<div class="chapter-beginning"/> +<h2>III.</h2> + + +<p>Let us now recapitulate the ancestral chain +of man, as it is set forth in the accompanying +diagram (p. <a name="FNanchor_55_55" id="FNanchor_55_55"></a><a href="#Footnote_55_55" class="label">55</a>), which represents our present +knowledge of our descent. For simplicity's +sake the many side-issues or branches which +lead to groups not in the main line of our +descent have been left out, or have been indicated +merely. Many of the stages are of +course hypothetical, arrived at by the study +of comparative anatomy and ontogeny; but +an example for each of them has been taken +from those living or fossil creatures which +seem to be their nearest representatives.</p> + +<p>1. The most remote ancestors of all living +organisms were living beings of the simplest +imaginable kind, organisms without organs,<span class="pagenum"><a name="Page_48" id="Page_48">[Pg 48]</a></span> +like the still existing <i>Monera</i>. Each consisted +of a simple granule of protoplasm, a +structureless mass of albuminous matter or +plasson, like the recent Chromaceæ and +Bacteriæ. The morphological value of these +beings is not yet that of a cell, but that of a +cytode, or cell without a nucleus. Cytoplasm +and nucleus were still undifferentiated.</p> + +<p>I assume that the first Monera owe their +existence to spontaneous creation out of so-called +anorganic combinations, consisting of +carbon, hydrogen, oxygen, and nitrogen. An +explanation of this hypothesis I have given +in my 'Generelle Morphologie.'</p> + +<p>The Monera probably arose early in the +Laurentian period. The oldest are the +Phytomonera, with vegetable metabolism. +They possessed the power (characteristic of +plants) of forming albumin by synthesis from +carbon, water, and ammonia. From some of +these plasma-forming Monera arose the +plasmophagous Zoomonera with animal metabolism, +living directly upon the produce of<span class="pagenum"><a name="Page_49" id="Page_49">[Pg 49]</a></span> +their plasmodomous or plasma-forming +sisters. This is the first instance of the +great principle of division of labour.</p> + +<p>2. The second stage is that of the <i>simple +and single cell</i>, a bit of protoplasm with a +nucleus. Such unicellular organisms are +still very common. The <i>Amœbæ</i> are their +simplest representatives. The morphological +value of such beings is the same as that of +the egg of any animal. The naked egg cells +of the sponges creep about in an amœboid +fashion, scarcely distinguishable from Amœba. +The same remark applies to the egg-cell of +man himself in its early stages before it is +enclosed in a membrane. The first unicellular +organisms arose from Monera through differentiation +of the inner nucleus from the outer +protoplasm.</p> + +<p>3. Repeated division of the unicellular +organism produces the <i>Synamœbium</i>, or +community of Amœbæ, provided the divisional +products, or new generations of the +original cell, do not scatter, but remain<span class="pagenum"><a name="Page_50" id="Page_50">[Pg 50]</a></span> +together. The existence of such a <i>Cœnobium</i>, +a number of equal and only loosely-connected +cells, as a separate stage in the ancestral +history of animals, is made highly probable by +the fact that the eggs of all animals undergo +after fertilization such a process of repeated +self-division, or 'cleavage,' until the single +egg cell is transformed into a heap of cells +closely packed together, not unlike a mulberry +(<i>morula</i>)—hence <i>morula</i> stage in ontogeny.</p> + +<p>4. The morula of most animals further +changes into a <i>Blastula</i>, a hollow ball filled +with fluid, the wall being formed by a single +layer of cells, the blastoderm or germinal layer. +This modification is brought about by the +action of the cells—they conveying nourishing +fluid into the interior of the whole cell +colony and thereby being themselves forced +towards the surface. The Blastula of most +Invertebrata, and even that of Amphioxus, is +possessed of fine ciliæ, or hair-like processes, +the vibrating motion of which causes the +whole organism to rotate and advance in<span class="pagenum"><a name="Page_51" id="Page_51">[Pg 51]</a></span> +the water. Living representatives of such +Blastæads, namely, globular gelatinous +colonies of cells enclosing a cavity, are +Volvox and Magosphæra.</p> + +<p>5. The Blastula of most animals assumes +a new larval form called <i>Gastrula</i>, in which +the essential characteristics are that a portion +of the blastoderm by invagination converts +the Blastula into a cup with double walls, +enclosing a new cavity, the primitive gut. +This invagination or bulging-in obliterates +the original inner cavity of the Blastula. +The outer layer of the Gastrula is the ectoderm, +the inner the endoderm; both pass +into each other at the blastoporus, or opening +of the gut cavity. The Gastrula is a stage +in the embryonic development of the various +great groups of animals, and some such +primitive form as ancestral to all Metazoa is +thus indicated. This hypothetical <i>Gastræa</i> +is still very essentially represented by the +lower Cœlenterates—<i>e.g.</i>, Olynthus, Hydra.</p> + +<p>6. The sixth stage—that of the <i>Platodes</i>,<span class="pagenum"><a name="Page_52" id="Page_52">[Pg 52]</a></span> +or flat-worms—is very hypothetical. They +are bilateral gastræads, with a flattened +oblong body, furnished with ciliæ, with a +primitive nervous system, simple sensory and +reproductive organs, but still without appendages, +body cavity, vent, and blood-vessels. +The nearest living representatives of such +creatures are the acœlous Turbellarians—<i>e.g.</i>, +Convoluta, a free-swimming, ciliated creature.</p> + +<p>7. The next higher stage is represented +by such low animals as the <i>Gastrotricha</i>—<i>e.g.</i>, +Chætonotus among the Rotatoria, which +differ from the rhabdocœlous Turbellarians +chiefly by the formation of a vent and the +beginnings of a cœlom, or cavity, between +gut and body wall. The addition of a primitive +vascular system and a pair of nephridia, +or excretory organs, is first met with in the +<i>Nemertines</i>.</p> + +<p>8. These, together with the <i>Enteropneusta</i> +(Balanoglossus), are comprised under the +name of Frontonia, or Rhynchelminthes, +and form the highest group of the Vermalia.</p> + +<p><span class="pagenum"><a name="Page_53" id="Page_53">[Pg 53]</a></span></p> + +<p>The Enteropneusta especially fix our attention, +because they alone, although essentially +'worms,' exhibit certain characteristics which +make it possible to bridge over the gulf +which still separates the Invertebrata from +the vertebrate phylum. The anterior portion +of the gut is transformed into a breathing +apparatus—hence Gegenbaur's term of Enteropneusta, +or Gut-breathers. Moreover, +Balanoglossus and Cephalodiscus possess +another modification of the gut—namely, a +peculiar diverticulum, which, in the present +state of our knowledge, may be looked upon +as the forerunner of the chorda dorsalis.</p> + +<p>9. Stage of <i>Prochordonia</i>, as indicated by +the larval form, called Chordula, which is +common to the Tunicata and all the Vertebrata. +These two groups possess three most +important features: (<i>a</i>) A chorda dorsalis, +a stiff rod lying in the long axis of the +body, dorsally from the gut and below the +central nervous system. This latter, for the +first time in the animal kingdom, appears in<span class="pagenum"><a name="Page_54" id="Page_54">[Pg 54]</a></span> +the shape of a spinal cord. (<i>b</i>) The use of +the anterior portion of the gut for respiratory +purposes. (<i>c</i>) The larval development of +the Tunicata is essentially the same as that of +the Vertebrata in its early stages. Only the +free-swimming Copelata or Appendicularia +among the Tunicates retain most of these +features. The others, which become sessile—namely, +the Ascidiæ, or sea-squirts—degenerate +and specialize away from the +main line.</p> + +<p class="center"> +<a name="Footnote_55_55" id="Footnote_55_55"></a><a href="#FNanchor_55_55"><span class="label">ANCESTRAL TREE OF THE VERTEBRATA</span></a><br /> +<i>Abridged from 'Systemat. Phylogenie,' § 15.</i><br /> +Names underlined refer to hypothetical groups.</p> + +<table id="atv" summary="vertebrata"> + +<tr> + <td class="tdc"><i>Aves</i></td> + <td class="tdc"> </td> + <td class="tdc"><i>Mammalia</i></td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdc"><i>Reptilia</i></td> + <td class="tdc">|</td> +</tr> +<tr> + <td class="tdr">'———</td> + <td class="tdl">———|</td> + <td class="tdc">|</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdr">|———</td> + <td class="tdl">———'</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdc">|</td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdc"><i>Proreptilia</i></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdc"><i>Pisces</i></td> + <td class="tdc">|</td> + <td class="tdc"><i>Amphibia</i></td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdr">|———</td> + <td class="tdl">———'</td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdc"><i>Stegocephali</i></td> + <td class="tdc"><i>Dipnoi</i></td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdr">|———</td> + <td class="tdl">———'</td> +</tr> +<tr> + <td class="tdr">'———</td> + <td class="tdl">———|</td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdc"><i>Proselachii</i></td> + <td class="tdc"><i> Cyclostomata</i></td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdc">|</td> + <td class="tdc">|</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdr">|———</td> + <td class="tdl">———'</td> +</tr> +<tr> + <td class="tdl"> </td> + <td class="tdc">|</td> + <td class="tdr"> </td> +</tr> +<tr> + <td class="tdc"> <i>Tunicata</i> </td> + <td class="tdc"> <span class="u"><i>Archicrania</i></span></td> + <td class="tdc"><i>Acrania</i></td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdr">|———</td> + <td class="tdl">———'</td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdc"><span class="u"><i>Prospondylia</i></span></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdr">'———</td> + <td class="tdl">———|</td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdc"><span class="u"><i>Prochordonia</i> </span></td> + <td class="tdr"></td> +</tr> +</table> + +<p>10. Stage of the <i>Acrania</i>, represented by +Amphioxus. The early development of this +little marine creature agrees closely with that +of the Tunicates; but one important feature +is added to its organization—namely, metamerism, +segmentally arranged mesoderm. +Amphioxus still possesses neither skull nor +vertebræ, neither ribs nor jaws, and no limbs. +But it is a member of the Vertebrata if we +define these as follows: Bilateral symmetrical +animals with segmentally arranged mesoderm, +with a chorda dorsalis between the +<span class="pagenum"><a name="Page_55" id="Page_55">[Pg 55]</a></span> +<span class="pagenum"><a name="Page_56" id="Page_56">[Pg 56]</a></span> +tubular nervous system and the gut, and with +respiratory organs which arise from the anterior +portion of the gut. We do not assume +that Amphioxus stands in the direct ancestral +line; it is probably much specialized, partly +degenerated, and represents a side-branch; +but it is, nevertheless, the only creature, +hitherto known, which satisfactorily connects +the Vertebrata with their invertebrate ancestors. +Many other efforts have been made to +solve the mystery of the origin of the Vertebrata—all +less satisfactory than the present +suggestion, or even absolutely futile. This +remark applies especially to the attempts +to derive them from either Articulata or +Echinoderms. The other great and highly +developed phylum, the Mollusca, is quite +out of the question. We have to go back to +a level at which all these principal phyla +meet, and there we find the Vermalia, the +lower of which alone permit connection in an +upward direction with the higher phyla.</p> + +<p>11. Stage of <i>Cyclostomata</i>. This now<span class="pagenum"><a name="Page_57" id="Page_57">[Pg 57]</a></span> +small group of Lampreys and Hagfishes +represents the lowest Craniota; and although +much specialized as a side-branch of the +main-stem from which the other Craniota +have sprung, they give us an idea of what +the direct ancestors of the latter must have +been like:—still without visceral arches, +without jaws and without paired limbs; with +a persistent pronephros; the ear with one +semicircular canal only; mouth suctorial; +cranium very primitive; and the metamerism +of the vertebral column indicated only by +little blocks of cartilage in the perichordal +sheath. Such creatures must have existed +at least as early as the Lower Silurian +epoch; but until 1890 fossil Cyclostomes were +unknown. Their life in the mud, or as +endoparasites of fishes, coupled with their +soft structure, makes them very unfit for +preservation. This gives all the greater importance +to Traquair's discovery, in 1890, of +many little creatures, called by him <i>Palæospondylus +gunni</i>, in the Old Red Sandstone of<span class="pagenum"><a name="Page_58" id="Page_58">[Pg 58]</a></span> +Caithness, which seem to be very closely +allied to Cyclostomata.</p> + +<p>12. The <i>Elasmobranchi</i> (sharks and skates), +with their immediate forerunners, the Acanthodi +of the Devonian and Carboniferous age, +are the first typical fishes. That they existed +as far back as the Silurian age is proved by +many enamelled spines of the dermal armour, +chiefly from the dorsal fins. This higher +stage is characterized by the possession of +typical jaws, by visceral or gill-bearing arches, +and by two pairs of limbs. None of the +Elasmobranchs, fossil or recent, stands in the +direct ancestral line; but they are the lowest +Gnathostomata, jaw-and-limb-possessing +creatures, known.</p> + +<p>13. Closely connected with the Elasmobranchs +in a wider sense are the <i>Crossopterygii</i>, +which begin in the Devonian age as a +large group, but have left only two survivals, +the African Polypterus and Calamoichthys. +They are possessed of dermal bones and +other ossifications, and are characterized by<span class="pagenum"><a name="Page_59" id="Page_59">[Pg 59]</a></span> +their lobate paired fins, which have a thick +axis beset with biserial fin rays. Their gill-clefts +are covered by an operculum, and they +have a well-developed air-bladder. Whilst +they are in many respects more highly +developed than the Elasmobranchs, and are +intimately connected with the typical Ganoids +and other bony fishes (all of which form a +great, manifold side-branch of the general +vertebrate stem), they stand in many other +respects (notably, the structure of the paired +fins, the vertebral column, and the air-bladder) +nearer the main-stem of our own +ancestral line.</p> + +<p>14. This is shown by their intimate +relation to the <i>Dipnoi</i>, which are still represented +by the Australian, African, and South +American mud-fishes: Ceratodus, Protopterus, +and Lepidosiren. The genus Ceratodus +existed in the Upper Trias, whence various +other unmistakably dipnoous forms lead down +through the Carboniferous (<i>e.g.</i>, Ctenodus) +to the Devonian strata—<i>e.g.</i>, Dipterus. They<span class="pagenum"><a name="Page_60" id="Page_60">[Pg 60]</a></span> +are characterized as follows: The paired fins +still retain the archipterygial form (namely, +one axis with biserial rays); the heart is +already trilocular, and receives blood which +is mixed arterial and venous, owing to the +gills being retained, while the air-bladder has +been modified into a lung. In fact, the +generalized Dipnoi form the actual link between +fishes and <i>Amphibia</i>.</p> + +<p>15. <i>Amphibia.</i> The earliest amphibian +fossils occur in the Carboniferous strata. +They alone—the Stegocephali or Phractamphibia—stand +in the ancestral line, while the +Lissamphibia, to which all the recent forms +belong, are side-branches. The Stegocephali +are the earliest Tetrapoda, the archipterygial +paired fins having been transformed into +the pentadactyle fore and hind limbs, which +are so characteristic of all the higher Vertebrata. +The cranium is roofed over by dermal +bones, of which, besides others, supra-occipitals, +supra-orbitals, and supra-temporals +are always present. The lowest members<span class="pagenum"><a name="Page_61" id="Page_61">[Pg 61]</a></span> +(Branchiosauri) still retained gills besides +the lungs, while others (Microsauri) have +lost the gills. Be it remembered that all the +recent Amphibia still undergo the same metamorphosis +during their ontogenetic development.</p> + +<p>In the very important Temnospondyli, a +subgroup of the Stegocephali—<i>e.g.</i>, Trimerorhachis +of the Lower Red Sandstone or Lower +Permian—the component cartilaginous or +bony units which compose the vertebræ still +remained in a separate, unfused state, showing +at the same time an arrangement whence +has arisen that which is typical of the Amniota. +The same applies to the limbs and +their girdles. In fact, the Stegocephali, taken +as a whole, lead imperceptibly to the <i>Proreptilia</i>.</p> + +<p>16. <i>Proreptilia</i> are represented by the +Permian genera Eryops and Cricotus. Until +quite recently these and many other fossils +from the Carboniferous strata were looked +upon as Amphibia, while many undoubted<span class="pagenum"><a name="Page_62" id="Page_62">[Pg 62]</a></span> +fossil Amphibia were mistaken for reptiles, +as indicated by the frequent termination +'-saurus' in their names.</p> + +<p>The nearest living representative of these +extinct Proreptilia is the New Zealand +reptile Hatteria, or Sphenodon, close relations +of which are known from the Upper Trias; +while others—<i>e.g.</i>, Palæohatteria—have been +discovered in the Permian. Anyhow, Sphenodon +is the reptile which stands nearest to the +main stem of our ancestry.</p> + +<p>The most important characteristics of the +Reptilia, which mark a higher stage or level, +are (1) The entire suppression of the gills—although +during the embryonic development +the gill-clefts still appear in all reptiles, birds, +and mammals; (2) The development of an +amnion and an allantois, both for the embryonic +life only, but so characteristic that all +these animals are comprised under the name +of Amniota; (3) The articulation of the skull +with the first neck vertebræ by well-developed +condyles, either single (really triple) or<span class="pagenum"><a name="Page_63" id="Page_63">[Pg 63]</a></span> +double (such a condylar arrangement begins +with the Amphibia, but only the two lateral +condyles are developed, while the middle +portion, belonging to the basi-occipital element, +remains rudimentary<a name="FNanchor_22_22" id="FNanchor_22_22"></a><a href="#Footnote_22_22" class="fnanchor">[22]</a>); (4) The formation +of centra, or bodies of the vertebræ, +mainly by a ventral pair of the original quadruple +constituents, or arcualia.</p> + +<p>17. Between the Proreptilia and the Mammalia, +which latter occur in the Upper Triassic +epoch, we have necessarily to intercalate a +group of very low reptiles, which are still so +generalized that their descendants could +branch off either into the Reptilia proper or +into the Mammalia. The changes concerned +chiefly the brain and the heart; of the skele<span class="pagenum"><a name="Page_64" id="Page_64">[Pg 64]</a></span>ton, +the skull and the pelvis; and, of the +tegumentary structures, the formation of a +hairy covering. Many such creatures existed +in the Triassic epoch—namely, the <i>Theromorpha</i>—some +of which indeed possess so +many characteristics which otherwise occur +in the Mammalia only, that these creatures +have been termed <i>Sauro-Mammalia</i>. However, +it has to be emphasized that none of +the Theromorpha hitherto discovered fulfils +all the requirements which would entitle them +to this important linking position. They only +give us an approximate idea of what this link +was like.</p> + +<p>18. Stage of the <i>Promammalia</i>, or <i>Prototheria</i>. +The only surviving members are +the famous duck-bill, Ornithorhynchus, and +the spiny ant-eaters, Echidna and Proechidna, +of the Australian region. These few genera, +however, differ so much from one another in +various important respects that they cannot +but be remnants of an originally much larger +group. Indeed, many fossils from the Upper<span class="pagenum"><a name="Page_65" id="Page_65">[Pg 65]</a></span> +Triassic and from the Jurassic strata have +without much doubt to be referred to the +Prototheria. The Prototheria are typical +mammals, because they possess the following +characteristics: The heart is completely +quadrilocular; the blood is warm, and its red +corpuscles have, owing to the loss of their +nucleus, been modified from biconvex into +biconcave discs; they have a hairy coat and +sweat glands, and two occipital condyles; the +ilio-sacral connection is preacetabular; the +ankle-joint is cruro-tarsal; the quadrate bone +of the Reptilia has ceased to carry the under +jaw, which now articulates directly with the +squamosal portion of the skull. Their low +position is shown by the retention of the +following reptilian features: Complete coracoid +bones and a T-shaped interclavicle; a +cloaca, or common chamber for the passage +of the fæces, the genital and the urinary products; +they are still oviparous; the embryo +develops without a chorion, and is therefore +not nourished through a placenta. Even the<span class="pagenum"><a name="Page_66" id="Page_66">[Pg 66]</a></span> +milk glands, which are absolutely peculiar to +the Mammalia, are still in a very primitive +stage, and do not yet produce milk proper; +and there is only a temporary shallow marsupium.</p> + +<p>19. Stage of <i>Metatheria</i>, or <i>Marsupialia</i>, +are direct descendants of Prototheria; but +they show higher development by the reduction +of the coracoid bones and the interclavicle. +The original cloaca is divided into +a rectal chamber and a uro-genital sinus, completely +separated, at least in the males; they +are viviparous; the young are received into +a permanent marsupium, in the walls of which +are formed typical milk glands and nipples, +but the embryo is still devoid of a placenta, +although some recent marsupials show indications +of such an organ. The corpus callosum +in the brain is still very weak.</p> + +<p>Most of the marsupials are extinct. They +occur from the Upper Trias onwards, and +had in the Jurassic epoch attained a wide +distribution both in Europe and in America.<span class="pagenum"><a name="Page_67" id="Page_67">[Pg 67]</a></span> +Since the Tertiary epoch they have been +restricted to America and to the Australian +region, and are now represented by about 150 +species.</p> + +<p>20. Stage of <i>Prochoriata</i>, or early <i>Placentalia</i>: +a further development of the Metatheria +by the development of a placenta, loss +of the marsupium and the marsupial bones, +complete division by the perineum of the +anal and uro-genital chambers, stronger +development of the corpus callosum, or chief +commissure of the two hemispheres of the +brain.</p> + +<p>Placentalia must have come into existence +during the Cretaceous epoch. Up to that +time all the Mammalia seem to have +belonged to either Prototheria or to Metatheria; +but in the early Eocene we can +distinguish the main groups of Placentalia—namely, +(1) Trogontia, now represented by +the rodents; (2) Edentata, or sloths, armadilloes, +etc.; (3) Carnassia, or Insectivora +and Carnivora; (4) Chiroptera, or bats;<span class="pagenum"><a name="Page_68" id="Page_68">[Pg 68]</a></span> +(5) Cetomorpha, or whales and dugongs; +(6) Ungulata; (7) Primates. Of these +groups, the first and second, third and fourth, +fifth and sixth, can perhaps, to judge from +palæontological evidence, be combined into +three greater groups, as indicated by the +fossil Esthonychida, Ictopsida, and Condylarthra, +in addition to the ancestral Primates, +or Lemuravida, as the fourth large branch of +the ancestral-tree where this has reached the +placental level. Among none of the first +three branches can we look for the ancestors +of the Primates. The Lemuravida, therefore, +represent a branch equivalent to the three +other branches.</p> + +<p>21. Stage of <i>Lemures</i>, or <i>Prosimiæ</i>, comprising +the older members of the Primates, +consequently approaching most nearly to the +Lemuravida. The limbs are modified into +pentadactyle hands and feet of the arboreal +type, and are protected by nails. The dentition +is of the frugivorous or omnivorous type, +with an originally complete series of teeth,</p> + +<p><span class="pagenum"><a name="Page_69" id="Page_69">[Pg 69]</a></span></p> + +<p><span class="pagenum"><a name="Page_70" id="Page_70">[Pg 70]</a></span></p> + +<p>with milk teeth and with permanent. The +orbit is surrounded by a complete bony ring, +posteriorly by a fronto-jugal arch, but still +widely communicating with the temporal +fossa. The placenta is diffuse and non-deciduous.</p> +<p class= "center"> +ANCESTRAL TREE OF THE MAMMALIA.<br /> + +<i>'Systematische Phylogenie,' § 386.</i></p> + +<table id="atm" summary="mammalia" cellspacing="0"> +<tr> + <td class="tdc"></td> + <td class="tdc"><i><small>Perissodactyla</small></i></td> + <td class="tdc" ></td> + <td class="tdc" ><i>Homo</i></td> + <td class="tdc" ></td> + <td class="tdc" ><small><i>Carnivora</i></small></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl"><i><small>Artiodactyla</small></i></td> + <td class="tdc">|</td> + <td class="tdc">(<i><small>Litopterna</small></i>)</td> + <td class="tdc">|</td> + <td class="tdc"></td> + <td class="tdc"> |</td> + <td class="tdc"><small><i>Pinnipedia</i></small></td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdc"><i><small>Anthropoidae</small></i></td> + <td class="tdc"></td> + <td class="tdr">|——</td> + <td class="tdl"> ——'</td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdr">| —— </td> + <td class="tdl"> —— '</td> + <td class="tdc">|</td> + <td class="tdc"></td> + <td class="tdc">|</td> + <td class="tdc"></td> +</tr> +<tr> + <td class="tdr">'——</td> + <td class="tdl"> ——|</td> + <td class="tdc"></td> + <td class="tdc"><i><small>Catarhinæ</small></i></td> + <td class="tdc"></td> + <td class="tdc"><small><i>Carnassia</i></small></td> + <td class="tdc"></td> +</tr> +<tr> + <td class="tdc"></td> + <td class="tdr">'—— </td> + <td class="tdl"> —— ,</td> + <td class="tdc">|</td> + <td class="tdc"></td> + <td class="tdc">|</td> + <td class="tdc"><i><small>Chiroptera</small></i></td> +</tr> +<tr> + <td class="tdc"><small>(<i>Amblypoda</i>)</small></td> + <td class="tdc"><i><small>Proboscidea</small></i></td> + <td class="tdc">|</td> + <td class="tdc"><i><small>Platyrhinæ</small></i></td> + <td class="tdc"><i><small>Insectivora</small></i></td> + <td class="tdc">|</td> + <td class="tdc">|</td> +</tr> +<tr> + <td class="tdr">'——</td> + <td class="tdl">——|</td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdr">|——</td> + <td class="tdl"> ——'</td> + <td class="tdc">|</td> +</tr> +<tr> + <td class="tdc"></td> + <td class="tdr">' —— </td> + <td class="tdl"> —— |</td> + <td class="tdc"><i><small>Simiæ</small></i></td> + <td class="tdc">|</td> + <td class="tdc"></td> + <td class="tdc">|</td> +</tr> +<tr> + <td class="tdc"><small><i>Cetacea</i></small></td> + <td class="tdc"><i><small>Sirenia</small></i></td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdr">|——</td> + <td class="tdc">————</td> + <td class="tdl">——'</td> +</tr> +<tr> + <td class="tdr">|—— </td> + <td class="tdl">——'</td> + <td class="tdc">|</td> + <td class="tdc"><i><small>Lemures</small></i></td> + <td class="tdc">|</td> + <td class="tdc"><i><small>Rodentia</small></i></td> + <td class="tdl"></td> +</tr> +<tr> + <td class="tdc"><i><small>Cetomorpha</small></i></td> + <td class="tdc"></td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdl"></td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdc"><i><small>Hyracoidea</small></i></td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdr"><i><span class="u"><small>Ictopsales</small></span></i></td> + <td class="tdc">(<i><small>Tillodontia</small></i>)</td> + <td class="tdl"></td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdc"><i><span class="u"><small>Lemuravidæ</small></span></i></td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdc"></td> +</tr> +<tr> + <td class="tdr">'——</td> + <td class="tdc">——'——</td> + <td class="tdl"> —— |</td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdc"><i><small>Trogontia</small></i></td> + <td class="tdc"><i><small>Edentata</small></i></td> +</tr> +<tr> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc"><i><span class="u"><small>Condylarthrales</small></span></i></td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdr">|——</td> + <td class="tdl"> ——'</td> +</tr> +<tr> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdc"><i><span class="u"><small>Esthonychales</small></span></i></td> + <td class="tdc"></td> +</tr> +<tr> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdr">' —— </td> + <td class="tdr">——|——</td> + <td class="tdc">——'——</td> + <td class="tdl">——'</td> + <td class="tdc"></td> +</tr> +<tr> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc">|</td> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc"></td> +</tr> +<tr> + <td class="tdc" colspan="7">Eutheria s. Placentalia</td> + </tr> +<tr> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc">|</td> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc"></td> +</tr> +<tr> + <td class="tdc" colspan="3"><i><small>Marsupialia diprotodontia</small></i></td> + <td class="tdc">|</td> + <td class="tdc" colspan="3"><i><small>Marsupialia polyprotodontia</small></i></td> +</tr> +<tr> + <td class="tdc"></td> + <td class="tdr">'——</td> + <td class="tdc">————</td> + <td class="tdc">——|——</td> + <td class="tdc">————</td> + <td class="tdl">——'</td> + <td class="tdc"></td> +</tr> +<tr> + <td class="tdc" colspan="7">Metatheria</td> +</tr> +<tr> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc">|</td> + <td class="tdc"><i><small>Monotremata</small></i></td> + <td class="tdc"></td> + <td class="tdc"><small>(<i>Allotheria</i>)</small></td> +</tr> +<tr> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc">Prototheria</td> + <td class="tdc">|</td> + <td class="tdc"></td> + <td class="tdc">|</td> +</tr> +<tr> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdr">|——</td> + <td class="tdl">——'——</td> + <td class="tdc">————</td> + <td class="tdl">——'</td> +</tr> +<tr> + <td class="tdc" colspan ="7"><i><span class="u"><small>Hypotheria s. Promammalia</small></span></i></td> +</tr> +</table> +<p> +<i>Names in brackets indicate extinct groups.<br /> +Names <span class="u">underlined</span> indicate hypothetical groups or combinations.</i><br /> +</p> + +<p>22. Stage of <i>Simiæ</i>. Orbit completely +separated from the temporal fossa by an +inward extension of the frontal and malar +bones meeting the alisphenoid. Placenta consolidated +into a disc, and with a maternal +deciduous portion. Mammæ pectoral only. +The dental formula is 2.1.3.3. All the +fingers and toes are protected by flat nails. +The tail is long. The American prehensile-tailed +monkeys are a lower side-branch.</p> + +<p>23. Stage of <i>Catarrhinæ Cercopithecidæ</i>. +The dental formula is 2.1.2.3, owing to the +loss of one pair of premolars in each jaw. +The frontal and alisphenoid bones are in +contact, separating the parietal from the +malar bone; this feature is correlated with +the enlarged brain. The internarial septum<span class="pagenum"><a name="Page_71" id="Page_71">[Pg 71]</a></span> +is narrow, and the nostrils look forwards and +downwards instead of sidewards—hence the +term 'Catarrhinæ.' The external auditory +meatus is long and bony. The tail is long, +with the exception of <i>Macacus inuus</i>. The +body is covered with a thick coat of furry +hair. Catarrhine monkeys have existed, we +know with certainty, since the Miocene.</p> + +<p>24. Stage of <i>Catarrhinæ Anthropoidæ</i>, or +<i>Apes</i>. Now represented by the large apes—namely, +the Hylobates or gibbon of South-Eastern +Asia, <i>Simia satyrus</i>, the orang-utan +of Sumatra and Borneo, <i>Troglodytes gorilla</i>, +<i>T. niger</i> and <i>T. calvus</i>, the gorilla and the +chimpanzees from Western Equatorial Africa. +Of fossils are to be mentioned Pliopithecus +and Dryopithecus from European Miocene, +and <i>Troglodytes sivalensis</i> from the Pliocene +of the Punjaub. The tail is reduced to a +few caudal vertebræ, which are transformed +into a coccyx, not visible externally; but in +the embryos of apes and man the tail is still +a conspicuous feature. The walk is semi<span class="pagenum"><a name="Page_72" id="Page_72">[Pg 72]</a></span>erect; +in adaptation to the prevailing arboreal +life, the arms are longer than the legs. +The hair of the body is considerably more +scanty than in the tailed monkeys. <i>Troglodytes +calvus</i>, a species or variety of chimpanzee, +is bald-headed. None of the recent +genera of apes can lay claim to a place in +the ancestry of mankind.</p> + +<p>25. Stage of <i>Pithecanthropi</i>. Hitherto the +only known representative is <i>Pithecanthropus +erectus</i>, from the Upper Pliocene of Java. In +adaptation to a more erect gait, the legs have +become stronger and the hind-hand has been +turned into a flat-soled walking 'foot.' The +brain is considerably enlarged. Presumably +it is still devoid of so-called articulate speech; +this is indicated by the fact that children +have to learn the language of their parents, +and by the circumstance that comparative +philology declares it impossible to reduce the +chief human languages to anything like one +common origin.</p> + +<p>26. <i>Man.</i> Known with certainty to have<span class="pagenum"><a name="Page_73" id="Page_73">[Pg 73]</a></span> +existed as an implement-using creature in the +last Glacial epoch. His probable origin +cannot, therefore, have been later than the +beginning of the Plistocene. The place of +origin was probably somewhere in Southern +Asia.</p> + +<p>Whilst we have to admit that there are +great defects in the older (invertebrate) +portion of our pedigree, we have all the more +reason to be satisfied with the positive results +of our investigation of the more recent (vertebrate) +part of it. All modern researches have +confirmed the views of Lamarck, Darwin, and +Huxley, and they allow of no doubt that the +nearest vertebrate ancestors of mankind were +a series of Tertiary Primates.</p> + +<p>Particularly valuable are the admirable +attempts of the two zoologists, Paul and Fritz +Sarasin,<a name="FNanchor_23_23" id="FNanchor_23_23"></a><a href="#Footnote_23_23" class="fnanchor">[23]</a> to throw light upon the human +phylogeny by painstaking comparison of all +the skeletal parts of man with those of the<span class="pagenum"><a name="Page_74" id="Page_74">[Pg 74]</a></span> +anthropoid apes. They have shown that +among the lower races of man the primitive +Veddahs of Ceylon approach the apes most +nearly, and that among the latter the chimpanzee +stands nearest to man.</p> + +<p>The direct descent of man from some +extinct ape-like form is now beyond doubt, +and admits of being traced much more clearly +than the origin of many another mammalian +order. The pedigrees of the Elephants, +the Sirenia, the Cetacea, and, above all, of +the Edentata, for example, are much more +obscure and difficult to explain. In many +parts of their organization—for example, in +the number and structure of his five digits and +toes—man and monkeys have remained much +more primitive than most of the Ungulata.</p> + +<p>The immense significance of this positive +knowledge of the origin of man from some +Primate does not require to be enforced. Its +bearing upon the highest questions of philosophy +cannot be exaggerated. Among modern +philosophers no one has perceived this more<span class="pagenum"><a name="Page_75" id="Page_75">[Pg 75]</a></span> +deeply than Herbert Spencer.<a name="FNanchor_24_24" id="FNanchor_24_24"></a><a href="#Footnote_24_24" class="fnanchor">[24]</a> He is one of +those older thinkers who before Darwin were +convinced that the theory of development +is the only way to solve the 'enigma of the +world.' Spencer is also the champion of those +evolutionists who lay the greatest weight +upon <i>progressive heredity</i>, or the much combated +<i>heredity of acquired characters</i>. From +the first he has severely attacked and criticised +the theories of Weismann, who denies +this most important factor of phylogeny, and +would explain the whole of transformism by +the 'all-sufficiency of selection.' In England +the theories of Weismann were received with +enthusiastic acclamation, much more so than +on the Continent, and they were called 'Neo-Darwinism,' +in opposition to the older conception +of Evolution, or 'Neo-Lamarckism.' +Neither of those expressions is correct. +Darwin himself was convinced of the fundamental +importance of progressive heredity<span class="pagenum"><a name="Page_76" id="Page_76">[Pg 76]</a></span> +quite as much as his great predecessor +Lamarck; as were also Huxley and Spencer.</p> + +<p>Three times I had the good fortune to +visit Darwin at Down, and on each occasion +we discussed this fundamental question in +complete harmony. I agree with Spencer +in the conviction that progressive heredity is +an indispensable factor in every true monistic +theory of Evolution, and that it is one of its +most important elements. If one denies +with Weismann the heredity of acquired +characters, then it becomes necessary to have +recourse to purely mystical qualities of germ-plasm. +I am of the opinion of Spencer, that +in that case it would be better to accept a +mysterious creation of all the various species +as described in the Mosaic account.</p> + +<p>If we look at the results of modern anthropogeny +from the highest point of view, and +compare all its empirical arguments, we are +justified in affirming that <i>the descent of man +from an extinct Tertiary series of Primates +is not a vague hypothesis, but an historical fact</i>.</p> + +<p><span class="pagenum"><a name="Page_77" id="Page_77">[Pg 77]</a></span></p> + +<p>Of course, this fact cannot be proved +<i>exactly</i>. We cannot explain all the innumerable +physical and chemical processes, +all the physiological mutations, which have +led during untold millions of years from the +simplest Monera and from the unicellular +Protista upwards to the chimpanzee and to +man. But the same consideration applies to +all historical facts. We all believe that +Aristotle, Cæsar, and King Alfred did live; +but it is impossible to give a proof within +the meaning of modern exact science. We +believe firmly in the former existence of +these and other great heroes of thought, +because we know well the works they have +left behind them, and we see their effects in +the history of human culture. These indirect +arguments do not furnish stronger evidence +than those of our history as vertebrates. +We know of many Jurassic mammals only +a single bone, the under jaw. We all +believe that these mammals possessed also +an upper jaw, a skull, and other bones. But<span class="pagenum"><a name="Page_78" id="Page_78">[Pg 78]</a></span> +the so-called 'exact school,' which regards +the transformation of species as a hypothesis +not proven, must suppose that the +mandibula was the only bone in the body of +these curious animals.</p> + +<p>Looking forward to the twentieth century, +I am convinced that it will universally accept +our theory of descent, and that future science +will regard it as the greatest advance made +in our time. I have no doubt that the +influence of the study of anthropogeny upon +all other branches of science will be fruitful +and auspicious. The work done in the +present century by Lamarck and Darwin +will in all future times be considered one +of the greatest conquests made by thinking +man.</p> + +<p><span class="pagenum"><a name="Page_79" id="Page_79">[Pg 79]</a></span></p> + +<p class="center">EVOLUTIONARY STAGES OF THE PRINCIPAL +GROUPS OF VERTEBRATA.<a name="FNanchor_25_25" id="FNanchor_25_25"></a><a href="#Footnote_25_25" class="fnanchor">[25]</a> </p> +<table id="esv" summary="stages"> +<tr> + <td class="tdc"><small>STAGES OF THE</small></td> + <td class="tdc"><small> CLASSES.</small></td> + <td class="tdc"><small>STAGES OF THE HEART.</small></td> +</tr> +<tr> + <td class="tdc"><small>PAIRED LIMBS.</small></td> + <td class="tdc"></td> + <td class="tdc"></td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">{1. <i>Acrania.</i></td> + <td class="tdl">I. <i>Leptocardia.</i></td> +</tr> +<tr> + <td class="tdl">I. <i>Adactylia</i></td> + <td class="tdl">{</td> + <td class="tdl"> Cold-blooded; heart</td> +</tr> +<tr> + <td class="tdl"> s. <i>Impinnata</i>.</td> + <td class="tdl">{</td> + <td class="tdl"> with one chamber;</td> +</tr> +<tr> + <td class="tdl"> Without jaws</td> + <td class="tdl">{</td> + <td class="tdl"> without lungs.</td> +</tr> +<tr> + <td class="tdl"> and limbs.</td> + <td class="tdl">{</td> + <td class="tdl"></td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">{2. <i>Cyclostomata.</i></td> + <td class="tdl">}II. <i>Ichthyocardia.</i></td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl"></td> + <td class="tdl">} Cold-blooded; heart</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl"></td> + <td class="tdl">} two-chambered, with</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl"></td> + <td class="tdl">} one atrium and one</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl"></td> + <td class="tdl">} ventricle; heart</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl"></td> + <td class="tdl">} containing venous</td> +</tr> +<tr> + <td class="tdl">II. <i>Polydactylia</i></td> + <td class="tdl">{3. <i>Pisces.</i></td> + <td class="tdl">} blood only; without lungs</td> +</tr> +<tr> + <td class="tdl"> s. <i>Pinnata</i>.</td> + <td class="tdl">{</td> + <td class="tdl"></td> +</tr> +<tr> + <td class="tdl"> With two</td> + <td class="tdl">{</td> + <td class="tdl"></td> +</tr> +<tr> + <td class="tdl"> pairs of fins.</td> + <td class="tdl">{ 4. <i>Dipnoi.</i></td> + <td class="tdl">}III. <i>Amphicardia.</i></td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl"></td> + <td class="tdl"> }Cold-blooded; heart</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl"></td> + <td class="tdl">} with three complete</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl"></td> + <td class="tdl">} chambers, namely, with</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl"></td> + <td class="tdl">} two atria and one</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">{ 5. <i>Amphibia.</i></td> + <td class="tdl">} ventricle, or (Reptilia)</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">{</td> + <td class="tdl">} two ventricles with still</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">{</td> + <td class="tdl">} incomplete septum; heart</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">{</td> + <td class="tdl">} containing mixed venous</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">{</td> + <td class="tdl">} and arterialized</td> +</tr> +<tr> + <td class="tdl">III. <i>Pentadactylia</i></td> + <td class="tdl">{ 6. <i>Reptilia.</i></td> + <td class="tdl">} blood; with lungs.</td> +</tr> +<tr> + <td class="tdl"> s. <i>Tetrapoda</i>.</td> + <td class="tdl">{</td> + <td class="tdl"></td> +</tr> +<tr> + <td class="tdl"> With two</td> + <td class="tdl">{</td> + <td class="tdl">{IV. <i>Thermocardia.</i></td> +</tr> +<tr> + <td class="tdl"> pairs of</td> + <td class="tdl">{</td> + <td class="tdl">{ Warm-blooded; heart</td> +</tr> +<tr> + <td class="tdl"> pentadactyle</td> + <td class="tdl">{</td> + <td class="tdl">{ with four complete</td> +</tr> +<tr> + <td class="tdl"> limbs (unless</td> + <td class="tdl">{7. <i>Aves.</i></td> + <td class="tdl">{ chambers, namely, two</td> +</tr> +<tr> + <td class="tdl"> they have</td> + <td class="tdl">{</td> + <td class="tdl">{ auricles and two</td> +</tr> +<tr> + <td class="tdl"> been lost by</td> + <td class="tdl">{</td> + <td class="tdl">{ ventricles; right half</td> +</tr> +<tr> + <td class="tdl"> reduction).</td> + <td class="tdl">{</td> + <td class="tdl">{ of the heart with venous,</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">{</td> + <td class="tdl">{ left half with arterialized,</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">{8. <i>Mammalia.</i></td> + <td class="tdl">{ blood; with lungs.</td> +</tr> +</table> + + +<p><span class="pagenum"><a name="Page_80" id="Page_80">[Pg 80]</a></span></p> + +<hr class="chap"/> +<div class="chapter-beginning"/> +<h2>BIOGRAPHICAL SKETCHES</h2> + + +<p><span class="smcap"><a name="Footnote_40" id="Footnote_40"></a><a href="#FNanchor_40">Jean Baptiste de Monet</a>, Chevalier de +<a name="Footnote_44" id="Footnote_44"></a><a href="#FNanchor_44">Lamarck</a></span>, was born on August 1, 1744, in +Picardy, where his father owned land. +Originally educated for the Church, he +soon enlisted, and distinguished himself in +active service. Owing to an accident affecting +his health, the young Lieutenant gave +up the military career, and, without means, +studied medicine and natural sciences at +Paris. In 1778 appeared his 'Flore française.' +In 1793 he was appointed to a +Chair of Zoology at the newly-formed Musée +d'Histoire Naturelle. He had the misfortune +to become gradually blind, and the last years +of his life were spent amid straitened circumstances. +He died in 1829.</p> + +<p><span class="pagenum"><a name="Page_81" id="Page_81">[Pg 81]</a></span></p> + +<p>In 1794 Lamarck divided the whole animal +kingdom into vertebrate and invertebrate +animals, and founded successively the groups +of Crustacea, Arachnida, Annelida, and +Radiata. Between 1816 and 1822 he published +his celebrated 'Histoire naturelle des +Animaux sans Vertèbres.'</p> + +<p>His most famous work is the 'Philosophie +zoologique,' 1809.</p> + +<p>Assuming the spontaneous origin of life, +he propounded the doctrine that all animals +and plants have arisen from low forms +through incessant modifications and changes. +In this respect he was in absolute opposition +to Cuvier, who upheld the immutability of +species, and did his best by absolute silence +to suppress the spread of the new doctrine.</p> + +<p>Lamarck has explained his views of transformism +chiefly in the seventh chapter of the +first volume of his 'Philosophie zoologique.'</p> + +<p>Organisms strive to accommodate or adapt +themselves to new circumstances, or to satisfy +new requirements—<i>e.g.</i>, climate, mode of<span class="pagenum"><a name="Page_82" id="Page_82">[Pg 82]</a></span> +procuring food, escape from enemies. The +continued function of parts of an organism +changes the old and produces new organs. +The acquirements are inherited by the offspring, +and thus are produced the more complicated +from simpler organisms. Continued +disuse brings about degeneration and ultimate +loss of an organ.</p> + +<p>Lamarck consequently sees in the adaptability, +or power of adaptation, which he +assumes for all living matter the ultimate +cause of variation; and, as he was certainly +the first to point out that acquired characters +are inherited by the progeny, he has given +a working explanation of Evolution.</p> + +<p>But his doctrine did not spread—partly +because he was misunderstood. His theory, +that a new want, by making itself felt, exacts +from the animal new exertions, perhaps from +parts hitherto not used, until the want is +satisfied—this way of putting it sounds too +teleological to explain the yearned-for change +in a mechanical or natural way. Moreover,<span class="pagenum"><a name="Page_83" id="Page_83">[Pg 83]</a></span> +many of his examples lacked the exact basis +of experiment and observation necessary for +their acceptance. Witness that of the neck of +the giraffe,—a never-failing source of ridicule +to men who cannot see the deeper purpose +underlying the well-meant attempt at an explanation, +which failed from want of complete +knowledge of the intricate circumstances.</p> + +<p>However, the theory of transformism was, +so to speak, in the air; and various authors +have written on the subject, filling the gap +between Lamarck and Darwin, especially +Goethe, Treviranus, Leopold von Buch, +and Herbert Spencer. But it is Darwin's +immortal merit to have opened our eyes by +his theory of natural selection, which is, at +least, the first attempt to explain some of the +causes and incidents of organic Evolution +in a natural mechanical way. Moreover, he +was the first clearly to express the fundamental +principles of the theory of descent, to +elaborate what had been at best a general +sketch of an ill-defined problem, and to enter<span class="pagenum"><a name="Page_84" id="Page_84">[Pg 84]</a></span> +into detail, supported by a host of painstaking +observations, the making of which had +taken him half a lifetime. Darwin, without +going further than cursorily into the causes +of variation, argued as follows: We know +that variations do occur in every kind of +living creatures. Some of these variations +lead to something, while others do not. An +enormously greater number of animals and +plants are born than reach maturity and can +in their turn continue the race. What is the +regulating factor? His answer is, The +struggle for existence—in other words, the +weeding out of the less fit, or rather of the +owners of those variations which are not so +well adapted to their surroundings.</p> + +<p>For 'adapted' we had better read 'adaptable,' +because a variation which does not +answer, which cannot be made use of, or, +still more notably, is a hindrance or disadvantage, +does not become an adapted +feature. There is often a confusion between +adaptation as an accomplished fact, a feature,<span class="pagenum"><a name="Page_85" id="Page_85">[Pg 85]</a></span> +or resultant condition, and adaptation as the +mode of fitting the organism to, or making +the best of, the prevailing surroundings or +circumstances.</p> + + +<p><span class="smcap">Étienne Geoffroy Saint-Hilaire</span> was +born in 1772 at Étampes, Seine-et-Oise. +He was originally brought up for the Church; +but when already ordained he attended +lectures on natural science and medicine in +Paris. He managed to get the place of +assistant in the Musée d'Histoire Naturelle; +he became Professor of Zoology in 1793, and +took the opportunity of encouraging young +Cuvier. Later he became Professor of +Zoology of the Faculté des Sciences, and in +1818 he published his remarkable 'Philosophie +anatomique.' He died in 1844.</p> + +<p>He had conceived the 'unity of organic +composition,' meaning that there is only one +plan of construction,—the same principle, but +varied in its accessory parts. In 1830, when +Geoffroy proceeded to apply to the Inverte<span class="pagenum"><a name="Page_86" id="Page_86">[Pg 86]</a></span>brata +his views as to the uniformity of +animal composition, he found a vigorous +opponent in Cuvier. Geoffroy, like Goethe, +held that there is in Nature a law of compensation, +or balancing of growth, so that if +one organ take on an excess of development, +it is at the expense of another part; and he +maintained that, since Nature takes no +sudden leaps, even organs which are superfluous +in any given species, if they have +played an important part in other species of +the same family, are retained as rudiments, +which testify to the permanence of the +general plan of creation. It was his conviction +that, owing to the conditions of life, +the same forms had <i>not</i> been perpetuated +since the origin of all things, although it was +not his belief that existing species were becoming +modified. Cuvier, on the other +hand, maintained the absolute invariability +of species, which, he declared, had been +created with regard to the circumstances in +which they were placed, each organ con<span class="pagenum"><a name="Page_87" id="Page_87">[Pg 87]</a></span>trived +with a view to the function it had to +fulfil,—thus putting the effect for the cause +('Encyclopædia Britannica,' 9th edition, +vol. xxi., p. 171).</p> + + +<p><span class="smcap">George <a name="Footnote_46" id="Footnote_46"></a><a href="#FNanchor_46">Cuvier</a></span> +in the department of Doubs, which +at that time belonged to Württemberg. He +was educated at Stuttgart, and studied +political economy. While acting as private +tutor to a French family in France he +followed his favourite pursuit, the study of +natural sciences. Geoffroy Saint-Hilaire +heard of him, and appointed him assistant in +the department of comparative anatomy in the +Musée d'Histoire Naturelle. In 1799 he was +elected Professor of Natural History at the +Collège de France, and soon after he became +Perpetual Secretary of the Institut National. +In 1831, a year before his death, Louis +Philippe raised him to the rank of a peer of +France.</p> + +<p>Cuvier was the first to indicate the true<span class="pagenum"><a name="Page_88" id="Page_88">[Pg 88]</a></span> +principle upon which the natural classification +of animals should be based—namely, +their structure. It is the study of the +anatomy of the creatures and their comparison +which affords the only sound basis +of a classification. The work which had the +greatest influence upon the scientific public +is his 'Règne animal distribué d'après son +Organisation,' 1817. The system which he +propounded in this book gradually came to +have almost world-wide fame, and, in spite +of its many obvious deficiencies, still lingers +in some of our most recent text-books.</p> + +<p>A standard work is his 'Leçons d'Anatomie +comparée,' and, in truth, he is the founder +of that kind of comparative anatomy which +was brought to such a high state by his +pupil, the late Sir Richard Owen. Cuvier +discovered the law of 'correlation of growth,' +and was the first to apply this law to the +reconstruction of animals from fragments: +see his monumental work entitled 'Recherches +sur les Ossemens fossiles,' 1812.</p> + +<p><span class="pagenum"><a name="Page_89" id="Page_89">[Pg 89]</a></span></p> + +<p>Cuvier, however, as a strict matter-of-fact +man, was incapable of appreciating the speculative +conclusions which were drawn by his +contemporaries Saint-Hilaire and Lamarck. +On the contrary, he firmly stuck to the +doctrine of the immutability of species; and, +in order to account for the existence of +animals whose kind exists no longer, he invented +the famous doctrine of successive +cataclysms.</p> + + +<p><span class="smcap">Karl Ernst <a name="Footnote_41" id="Footnote_41"></a><a href="#FNanchor_41">von Baer</a></span> +was born in 1792 +in Esthonia, studied at Dorpat and then at +Würzburg, where Döllinger introduced him +to comparative anatomy. For a few years +he was a <i>Privat-docent</i> at Berlin; then he +went to Königsberg as Professor of Zoology +and Embryology. In 1834 he became an +Academician at St. Petersburg, where for +many years he was occupied with the most +varied studies, chiefly geographical and +ethnological. The last years of his long, +active life he spent in contemplative retire<span class="pagenum"><a name="Page_90" id="Page_90">[Pg 90]</a></span>ment +on his paternal estate, and he died at +Dorpat in 1876.</p> + +<p>While still at Würzburg he induced his +friend Pander, a young man of means, to study +the development of the chick; and Pander was +the first to start the theory of the germinal +layers from which all the organs arise. +Baer, however, continued these researches in +Königsberg, and after nine years' labour produced +his epoch-making work, 'Ueber Entwicklungsgeschichte +der Thiere: Beobachtung +und Reflexion,' Königsberg, 1828. Nine +years later he completed the second volume. +He established upon a firm basis the theory +of the germinal layers, and by further 'reflexions' +arrived at the elucidation of some of +the most fundamental laws of biology. For +example, in the first volume he made the +following prophetic statement: 'Perhaps all +animals are alike, and nothing but hollow +globes at their earliest developmental beginning. +The farther back we trace their +development, the more resemblance we find<span class="pagenum"><a name="Page_91" id="Page_91">[Pg 91]</a></span> +in the most different creatures. And this +leads to the question whether at the beginning +of their development all animals are essentially +alike, and referable to one common ancestral +form. Considering that the "germ" (which +at a certain stage appears in the shape of a +hollow globe or bag) is the undeveloped animal +itself, we are not without reason for assuming +that the common fundamental form is that of a +simple vesicle, from which every animal is +evolved, not only theoretically, but historically.'</p> + +<p>This statement is all the more wonderful +when we consider that the cells, the all-composing +individual units, were not discovered +until ten years later.</p> + +<p>In 1829 Baer discovered the human egg, +and later the chorda dorsalis. In an address +delivered in 1834, entitled 'The Most Universal +Law of Nature in all Development,' he +explained that only from a most superficial +point of view can the various species be looked +upon as permanent and immutable types;<span class="pagenum"><a name="Page_92" id="Page_92">[Pg 92]</a></span> +that, on the contrary, they can be nothing +but passing stages, or series of stages, of +development, which have been evolved by +transformation out of common ancestral forms.</p> + + +<p><span class="smcap">Johannes Mueller</span>, born at Coblenz in +1801, established himself as <i>Privat-docent</i> at +Bonn, where in 1830 he became Professor of +Physiology. In 1833 he accepted the Chair +of Anatomy and Physiology at Berlin, where +he died in 1858.</p> + +<p>He was one of the most distinguished +physiologists and comparative anatomists. +By summarizing the labours and discoveries +already made in the field of physiology, by +reducing them to order, and abstracting the +general principles, he became the founder of +modern physiology. But he was scarcely +less distinguished by his researches in +comparative anatomy. His 'Vergleichende +Anatomie der Myxinoiden,' in <i>Abhandlungen +der Berliner Akademie</i>, 1835-45, and 'Ueber +die Grenzen der Ganoiden' (<i>ibid.</i>, 1846), are +standard works of lasting value.</p> + +<p><span class="pagenum"><a name="Page_93" id="Page_93">[Pg 93]</a></span></p> + +<p>Mueller exercised a stimulative influence +as a teacher. Many well-known men—such +as Helmholtz, Gegenbaur, Bruecke the physiologist, +Guenther the zoologist, Virchow the +pathologist, Koelliker and Haeckel—have +been his pupils.</p> + + +<p><span class="smcap">Rudolph <a name="Footnote_45" id="Footnote_45"></a><a href="#FNanchor_45">Virchow</a></span> +Schievelbein, a small town in Eastern +Pomerania. He studied medicine in Berlin +as a pupil of Johannes Mueller, and went +in 1849 to Würzburg, where, under the +influence of Koelliker, and Leydig the pathologist, +he laid the foundation of an entirely +new branch of medical science—that of +'cellular pathology.' Since 1856 he has +filled the principal Chair of Pathology at +Berlin. In 1892 he received the Copley +medal of the Royal Society.</p> + +<p>'His contributions to the study of morbid +anatomy have thrown light upon the diseases +of every part of the body; but the broad +and philosophical view he has taken of the<span class="pagenum"><a name="Page_94" id="Page_94">[Pg 94]</a></span> +processes of pathology has done more than +his most brilliant observations to make the +science of disease.</p> + +<p>'In pathology, strictly so called, his two +great achievements—the detection of the +cellular activity which lies at the bottom of +all morbid as well as normal physiological +processes, and the classification of the important +group of new growths on a natural +histological basis—have each of them not +only made an epoch in medicine, but have +also been the occasion of fresh extension of +science by other labourers' (Proc. Royal +Soc., 1892).</p> + +<p>Virchow has not confined himself to +medicine. He takes the keenest interest in +anthropology and ethnology, on which subjects +he has contributed many papers. +Together with his colleagues Helmholtz the +physicist, and Du Bois Reymond the physiologist, +he has taken a leading place in the +spreading of natural science; but, unfortunately, +he did not take to the doctrine of<span class="pagenum"><a name="Page_95" id="Page_95">[Pg 95]</a></span> +Evolution, and for the last thirty years has +been its declared antagonist, rarely missing +an opportunity of denouncing everything but +descriptive anatomy and zoology as the +unsound speculations of dreamers. This has +on more than one occasion brought him into +sharp conflict with Haeckel. His activity is +astonishing, especially if it be remembered that +Virchow has for many years been one of the +most conspicuous leaders of the Progressists +and Radicals in the German Parliament and +Berlin town-council.</p> + + +<p><span class="smcap">Edward Drinker Cope</span> was born at +Philadelphia, Pa. After studying at several +Continental Universities, especially at Heidelberg, +he became first Professor of Natural +Science at Haverford College, and later +Professor of Geology and Mineralogy. He +died at an early age in 1897. As a member +of various geological expeditions and other +surveys, he explored chiefly Kansas, Wyoming, +and Colorado; and he published many<span class="pagenum"><a name="Page_96" id="Page_96">[Pg 96]</a></span> +most suggestive papers on the fossil vertebrate +fauna of North America, and on classification +especially of Amphibia and Reptiles.</p> + +<p>Among works of a more general philosophical +scope may be mentioned 'The +Origin of the Fittest,' 1887, and his latest +work, 'The Primary Factors of Organic +Evolution,' 1896.</p> + + +<p><span class="smcap">Albert von <a name="Footnote_50" id="Footnote_50"></a><a href="#FNanchor_50">Koelliker</a></span> +became Professor of Anatomy at Würzburg. +His earlier studies and discoveries contributed +considerably to the systematic development +of the cell theory. In 1844 he observed the +division and further multiplication of the +original egg cell. Next year he showed the +continuity between nerve cells and nerve +fibres in the Vertebrata; later, that the non-striped +or smooth muscular tissue is composed +of cellular elements. He demonstrated that +the Gregarinæ are unicellular creatures. In +1852 he went with his younger friend Gegenbaur +to Messina, where he studied especially<span class="pagenum"><a name="Page_97" id="Page_97">[Pg 97]</a></span> +the development of the Cephalopoda (cuttlefishes +and allies); and he produced a magnificent +work on Alcyonaria, Medusæ, and +other allied forms. He elucidated the development +of the vertebral column, especially +with reference to the notochord.</p> + +<p>In 1848 he founded, together with Th. von +Siebold, the famous <i>Zeitschrift für wissenschaftliche +Zoologie</i>.</p> + +<p>A standard work on mammalian embryology +is his 'Entwicklungsgeschichte +des Menschen und der höheren Thiere,' a +text-book of which the second edition +appeared in 1879.</p> + +<p>At the anniversary meeting of 1897 he +received the Copley medal, the highest honour +which the Royal Society can bestow.</p> + + +<p><span class="smcap">Carl <a name="Footnote_49" id="Footnote_49"></a><a href="#FNanchor_49">Gegenbaur</a> +</span> was born on August 21, +1826, in Bavaria. He studied medicine and +kindred subjects in Würzburg, and as a pupil +of Johannes Mueller in Berlin.</p> + +<p>In 1852 he went with Koelliker to Messina<span class="pagenum"><a name="Page_98" id="Page_98">[Pg 98]</a></span> +to study the structure and development of the +marine fauna. Important papers on Siphonophora, +Echinoderms, Pteropoda, and, later, +Hydrozoa and Mollusca, were the result. +Soon after his return he was offered the +chair of Anatomy at Jena, and at this retired +spot he produced his most important works, +devoting himself more and more to the study +of the Vertebrata. Since 1875 he has held +the Chair of Anatomy at Heidelberg.</p> + +<p>In 1859 he published his 'Principles of +Comparative Anatomy'; but in 1870 he remodelled +it completely, the theory of descent +being the guiding principle. These 'Grundzüge' +were followed by a somewhat more +condensed 'Grundriss,' the second edition of +which was published in 1878, and has been +translated into French and English. In the +meantime he had broken new ground by +the development and treatment of certain +problems concerning the composition and +origin of the limbs, the shoulder-girdle and +the skull, researches which are embodied<span class="pagenum"><a name="Page_99" id="Page_99">[Pg 99]</a></span> +in his 'Untersuchungen zur vergleichenden +Anatomie der Wirbelthiere,' 1864-65-72.</p> + +<p>In 1883 he brought out a text-book on +human anatomy. This also marked a new +epoch, because for the first time, not only the +nomenclature, but also the general treatment +of human anatomy, was put upon a firm +comparative anatomical basis. The success +of this work is indicated by the fact that it +reached the sixth edition in 1897.</p> + +<p>Lastly, in 1898, appeared the first volume +of what may be called his crowning work, +'Vergleichende Anatomie der Wirbelthiere.'</p> + +<p>Gegenbaur is universally recognised, not +only as the greatest living comparative +anatomist, but also as the founder of the +modern side of this science, by having based +it on the theory of descent.</p> + +<p>In 1896 he received from the Royal Society +the Copley medal 'for his pre-eminence in +the science of comparative anatomy or animal +morphology.'</p> + +<p>His marvellously powerful influence as a<span class="pagenum"><a name="Page_100" id="Page_100">[Pg 100]</a></span> +teacher and investigator has made Heidelberg +a centre whence many pupils have +spread his teaching, and above all his method +of research.</p> + + +<p><span class="smcap">Ernst Heinrich Haeckel</span> was born on +February 16, 1834, at Potsdam. He carried +out his academical studies alternately at +Berlin and Würzburg, attracted by such +men as Johannes Mueller, Koelliker, and +Virchow. For years he was undecided what +his career should be, whether that of botanist, +collector, or geographical traveller. Certainly +that of medicine attracted him least, although +in deference to his father's wishes he qualified +and settled down for a year's practice in +Berlin. As he himself has told us, he might +perhaps have proved rather successful as a +physician, to judge from the fact that he did +not lose a single patient. But 'I had only +three patients all told, and the reason of this +is perhaps that I had given on my plate the +hours of consultation as from 5 to 6 <i>a.m.</i>'</p> + +<p><span class="pagenum"><a name="Page_101" id="Page_101">[Pg 101]</a></span></p> + +<p>During the year 1859 he travelled as +medical man and artist in Sicily. In 1861 +he was induced by Gegenbaur, whose acquaintance +he had made in Würzburg, to +establish himself as a <i>Privat-docent</i> for comparative +anatomy in Jena. And there he +has remained ever since, filling the Chair of +Zoology, and having declined several much +more tempting offers from the Universities of +Würzburg, Vienna, Strassburg, and Bonn.</p> + +<p>Within one year, 1865, he wrote the two +volumes of his 'Generelle Morphologie der +Organismen,' as he himself relates, in order +to master his sorrow over the loss of his first +wife. But he broke down, and went to the +Canaries to recruit health and strength. The +'Morphologie,' which has long been out of +print,<a name="FNanchor_26_26" id="FNanchor_26_26"></a><a href="#Footnote_26_26" class="fnanchor">[26]</a> made scarcely any impression. It<span class="pagenum"><a name="Page_102" id="Page_102">[Pg 102]</a></span> +was ignored, probably because he had placed +the old-fashioned study of zoology and morphology +upon a thoroughly Darwinistic basis.</p> + +<p>On the advice of his friend Gegenbaur, he +gave a more popularly written abstract of +his 'Generelle Morphologie'—in fact, the +substance of a series of his lectures—in +the shape of his 'Natürliche Schöpfungsgeschichte.' +This 'History of Natural +Creation,' which in 1898 has reached the +ninth edition (first edition translated into +English in 1873), had the desired effect. +So also had his '<a name="Footnote_42" id="Footnote_42"></a><a href="#FNanchor_42">Anthropogenie</a> oder +<a name="Footnote_47" id="Footnote_47"></a><a href="#FNanchor_47">Entwicklungsgeschichte</a> des <a name="Footnote_51" id="Footnote_51"></a><a href="#FNanchor_51">Menschen</a>,' the +fourth edition of which appeared in 1891.</p> + +<p>It was a lucky coincidence that Haeckel +had just finished his preliminary academical +studies, was entirely at leisure, and undetermined +to which branch of natural science +he should devote his genius, when Darwin's +great work was given to the world. Haeckel +embraced the new doctrine fervently, and, +as Huxley was doing in England, he spread<span class="pagenum"><a name="Page_103" id="Page_103">[Pg 103]</a></span> +it and fought for it with ever-increasing +vigour in Germany.</p> + +<p>With marvellous vigour and quickness of +perception he applied the principles of Evolution +or the theory of descent to the whole +organic world, and not only opened entirely +new vistas for the study of morphology, +but also worked them out and fixed them. +He was the first to draw up pedigrees of +the various larger groups of animals and +plants, filling the gaps by fossils or with +hypothetical forms (the necessary existence +of which he arrived at by logical deductions); +and thus he reconstructed the first universal +pedigree, a gigantic ancestral tree, from the +simple unicellular Amœba to Man. Of course +these pedigrees were entirely provisional, as +he himself has over and over again avowed; +but they are, nevertheless, the ideal which all +systematists and morphologists working upon +the basis of Evolution have since been seeking +to establish.</p> + +<p>Naturally he was vigorously attacked, not<span class="pagenum"><a name="Page_104" id="Page_104">[Pg 104]</a></span> +only by anti-Darwinians, or rather anti-Evolutionists, +but also by many of those +who, having accepted the principle of transformism, +ought to have known better. +Perhaps they thought they did know better. +Imperfections or mistakes in details of the +grand attempt,—and these, naturally, were +many,—were singled out as samples of the +whole, which was ridiculed as the romance +of a dreamer.</p> + +<p>In the end, however, this hostility, narrow-minded +and unfair in many respects, has done +good to the cause. There has arisen an +ever-increasing school of workers in favour +of the new doctrine. Owing to renewed +research, criticism, corrections in all directions, +we now know considerably more about +natural classification (and this is pedigree) +than when Haeckel first opened out the +whole problem.</p> + +<p>Owing to his fearless mode of exposition, +regardless of the indignant wrath which the +new doctrine aroused in certain ecclesiastical<span class="pagenum"><a name="Page_105" id="Page_105">[Pg 105]</a></span> +quarters, Haeckel bore the brunt of almost +endless attacks, and had to write polemical +essays. The result has been that friend and +foe alike are now working on the lines which +he has laid down; most of the ideas which +he was the first to conceive, and to formulate +by inventing a scientific terminology for +them, have become important branches, or +even disciplines, of the science.</p> + +<p>Most morphologists of the younger generations +now take these terms for granted, without +remembering the name of their founder. +It is, therefore, perhaps not quite superfluous +to mention some of them:</p> + +<p><i>Phylum</i>, or stem, the sum total of all those +organisms which have probably descended +from one common lower form. He distinguished +eight such phyla—Protozoa, +Cœlenterata, Helminthes or Vermes, Tunicata, +Mollusca, Articulata, and Vertebrata. +The phyla are more or less analogous to +'super-classes,' large branches or 'circles,' or +principal groups of other zoologists.</p> + +<p><span class="pagenum"><a name="Page_106" id="Page_106">[Pg 106]</a></span></p> + +<p><a name="Footnote_43" id="Footnote_43"></a><a href="#FNanchor_43"><i>Phylogeny</i></a>, +the history of the <a name="Footnote_48" id="Footnote_48"></a><a href="#FNanchor_48">development</a> of the various <a name="Footnote_52" id="Footnote_52"></a><a href="#FNanchor_52">phyla</a>, classes, orders, +families,and species.</p> + +<p><i>Ontogeny</i>, the history or study of the +development of the individual, generally +called embryology. In reality the scope of +embryology is the ontogenetic study of the +various species, and this branch of developmental +study alone can be checked by direct, +'exact' observation, for the simple reason +that the individuals alone are entities, while +the species, genera, families, etc., are abstract +ideas.</p> + +<p>The <i>ontogenesis of any given living organism +is a short, condensed recapitulation of its +ancestral history or of its phylogenesis</i>. This +is Haeckel's 'fundamental biogenetic law.'</p> + +<p>A complete proof of the phylogeny of any +creature would be given by the preservation +of an unbroken series of all its fossil ancestors. +Such a series will in most cases, for obvious +reasons, always remain a desideratum. In a +few cases, however, the desideratum is nearly<span class="pagenum"><a name="Page_107" id="Page_107">[Pg 107]</a></span> +met: for example, the ancestral line of the +one-toed digitigrade horse from a four-or +five-toed plantigrade and still very generalized +Ungulate is approaching completion.</p> + +<p>Phylogenetic study has to rely upon other +help. This is afforded by comparative +anatomy and by the study of ontogeny. +If the latter were a faithful, unbroken recapitulation +of all the stages through which +the ancestors have passed, the whole matter +would be very simple; but we know for +certain that in the individual development +many stages are left out (or, rather, are +hurried through, and are so condensed by +short-cuts being taken that we cannot +observe them), while other features which +have been introduced obscure, and occasionally +modify beyond recognition, the original +course.</p> + +<p>Again, the sequence of the appearance +of the various organs is frequently upset +(<i>heterochronism</i>). Some organs are accelerated +in their development, while others,<span class="pagenum"><a name="Page_108" id="Page_108">[Pg 108]</a></span> +which we know to be phylogenetically older, +are retarded in making their reappearance in +the embryo.</p> + +<p>These disturbing or distorting newly introduced +features or factors show themselves +chiefly in connection with the embryonic conditions +of growth—for example, yolk-sac, +placenta, amnion. They all come within the +category of <i>cænogenesis</i>: they are cænogenetic, +while the true, undisturbed recapitulation is +<i>palingenetic</i>.</p> + +<p>Lastly, some features, so-called rudimentary +or vestigial organs, instead of disappearing, +are most tenacious in their recurrence, while +others of originally fundamental importance +scarcely leave recognisable traces, and are, so +to speak, only hinted at during the embryonic +growth of the creature we happen to study. +Hence arises the philosophical study of +'Dysteleology.'</p> + +<p>Among other terms invented by Haeckel, +and now in general use, are <i>Metamere</i>, +<i>Metamerism</i>, <i>Cœlom</i>, <i>Gonochorism</i>, <i>Gastrula</i>,<span class="pagenum"><a name="Page_109" id="Page_109">[Pg 109]</a></span> +<i>Metazoa</i>, <i>Gnathostomata</i>, <i>Acrania</i>, <i>Craniota</i>, +and <i>Amniota</i>.</p> + +<p>Hitherto we have dealt with his general +work only, a résumé of which he gave for +many years in a course of thirty lectures +before an audience composed of 'all sorts +and conditions of men.' Students of biology +and of medicine side by side with theologians, +incipient and ordained, jurists, political economists, +and philosophers, crowded his lecture-room +during the 'seventies to hear the master +explaining the 'natural history of creation' or +the mysteries of anthropogenesis. Another +course of eighty lectures during the winter +semester was, and still is, devoted to a +systematic treatment of zoology, while practical +classes are reserved for the more select.</p> + +<p>His winning personality and fascinating +eloquence, combined with a clear and concise +delivery, have gained the enthusiastic admiration +of many a student who went to the quiet +University town in order to learn with his +own ears and eyes.</p> + +<p><span class="pagenum"><a name="Page_110" id="Page_110">[Pg 110]</a></span></p> + +<p><i>List of Separate Publications by Professor +Haeckel.</i></p> + +<p>'Biologische Studien. I.: Studien ueber +die Moneren und andere Protisten.' Leipzig, +1870 (out of print). He was the first to +make observations on the natural history of +the Monera, living bits of protoplasm, devoid +even of a nucleus—<i>e.g.</i>, <i>Protogenes primordialis</i>, +<i>Protomyxa aurantiaca</i>.</p> + +<p>'Monographie der Radiolarien.' Berlin, +1862-88. With 171 plates.</p> + +<p>'Entwicklungsgeschichte der Siphonophoren.' +Utrecht, 1869.</p> + +<p>'Plankton-Studien. Vergleichende Untersuchungen +ueber die Bedeutung und +Zusammensetzung der pelagischen Fauna +und Flora.' Jena, 1880.</p> + +<p>'Metagenesis und Hypogenesis von +Aurelia aurita.' Jena, 1881.</p> + +<p>'Monographie der Geryoniden oder +Ruesselquallen.' Leipzig, 1865.</p> + +<p>'Generelle Morphologie der Organismen.' +2 vols. Berlin, 1866.</p> + +<p><span class="pagenum"><a name="Page_111" id="Page_111">[Pg 111]</a></span></p> + +<p>'Anthropogenie oder Entwicklungsgeschichte +des Menschen,' 1874; 4th edition, +1891.</p> + +<p>'Natuerliche Schoepfungs-Geschichte.' 2 +vols. Berlin, 1st edition, 1868; 9th edition, +1898. This work has been translated into +most European languages (the first edition in +English, under the title 'Natural History of +Creation' in 1873; the eighth in 1892).</p> + +<p>'Monographie der Kalkschwaemme.' 3 +vols. Berlin, 1872 (out of print). With the +subtitle, 'An Attempt to solve analytically +the Problem of the Origin of Species.' In +this work, illustrated by sixty plates, he +showed that the Calcispongia are individually +so yielding, so adaptive to external influences, +that it is practically impossible to break up +the whole group into anything like satisfactory +species or genera. According to +predilection, we can distinguish either 1 genus +with only 3 species, or 3, 21, 43 genera, with +21, 111, 181, or 289 species respectively.</p> + +<p>In this work, in 1872, Haeckel established<span class="pagenum"><a name="Page_112" id="Page_112">[Pg 112]</a></span> +the homology of the two primary layers, ecto- +and endoderm, throughout the Metazoa. +The attempt to do the same for the four +secondary layers, as made in the second part +of his 'Gastræa-theory,' failed. It caused +an enormous amount of research, hitherto +without a satisfactory solution of the problem.</p> + +<p>'Studien zur Gastræa-Theorie.' Jena, +1874. The transformation of the single +primitive egg-cell by cleavage into a globular +mass of cells (Morula)—which latter, becoming +hollow (and then known as the Blastula), +turns ultimately by invagination or by delamination +into the Gastrula—is a series of +processes which applies to all Metazoa. The +Gastrula is, therefore, the ancestral form of +the Metazoa; and the Gastræa-theory, +founded by Haeckel, throws light, on the one +hand, upon the mystery of the phyletic connection +of the various animal groups, while, +on the other hand, it connects the Metazoa, +or multicellular organisms, with the lowest +Protozoa. We come to this conclusion because<span class="pagenum"><a name="Page_113" id="Page_113">[Pg 113]</a></span> +the Gastrula arises from and passes +through stages which exist as independent, +permanent organisms among the Protozoa.</p> + +<p>Needless to say this Gastræa-theory has +been violently attacked in detail, with the +result that various modifications of the Gastrula, +until then undreamed of, have become +known.</p> + +<p>'Monographie der Medusen.' Jena, 1879-81. +With 72 coloured plates.</p> + +<p>'Reports on the Scientific Results of the +Voyage of H.M.S. <i>Challenger</i>.' With 230 +plates:</p> + +<blockquote> +<p>1. Deep-sea Medusæ. 1881.<br /> +2. Radiolaria. 1887.<br /> +3. Siphonophoræ. 1888.<br /> +4. Deep-sea Keratosa. 1889.<br /> +</p></blockquote> + +<p>A short holiday spent on the coasts of the +Red Sea produced the volume 'Arabische +Korallen' (Berlin, 1876); and a longer trip +to Ceylon has been described in 'Indische +Reisebriefe,' of which the third edition<span class="pagenum"><a name="Page_114" id="Page_114">[Pg 114]</a></span> +appeared in 1893. The English translation +(1883) is entitled 'A Visit to Ceylon.'</p> + +<p>'Monism as connecting Religion and +Science: the Confession of Faith of a Man +of Science.' 1894.</p> + +<p>Haeckels latest work is the 'Systematische +Phylogenie' (Berlin, 1896), three volumes +dealing with Protistæ and Plants, Invertebrata +and Vertebrata. They contain the author's +views on the natural system of the organic +world, both living and extinct. Notable in +the work are the many reconstructions of +ancestral forms which, provided Evolution is +true, must have existed—hypothetical until +they, or something like them, are found in a +fossil state. Everybody who works systematically, +and upon the basis of Evolution, +does, sometimes unconsciously, reconstruct +such links, although he may perhaps not see +the necessity, or have the courage to fix +his vision, by assigning to it all those attributes +or characters which are indicated by +deductions from comparative anatomy, palæontology, +and embryology.</p> + +<p><span class="pagenum"><a name="Page_115" id="Page_115">[Pg 115]</a></span></p> + +<hr class="chap"/> +<div class="chapter-beginning"/> +<h2>THEORY OF CELLS.</h2> + + +<p>The vegetable cell was discovered by +<i>Schleiden</i>, Professor of Botany at Jena, in +1838. Next year <i>Schwann</i> found the animal +cell.</p> + +<p>In 1844 <i>Koelliker</i> discovered that the egg +cell, by division and multiplication, becomes +an aggregation—a heap of new cells.</p> + +<p>In 1849 <i>Huxley</i> found the two primary +layers (observed long before by <i>Pander</i> and +<i>Baer</i> in the chick) also in certain Invertebrata, +the Medusæ; and he called these layers +'ectoderm' and 'endoderm' respectively.</p> + +<p>In 1851 <i>Remak</i>, in his 'Untersuchungen +über die Entwicklung der Thiere,' showed +the egg to be a simple cell, and that from it, +by repeated division or multiplication, arise<span class="pagenum"><a name="Page_116" id="Page_116">[Pg 116]</a></span> +the germinal layers, and that by differentiation +of the cells of these layers are formed +all the tissues of the body.</p> + +<p><i>Kowalevsky</i>, of St. Petersburg, found the +two primary germinal layers also in Worms, +Echinoderms, Articulata, and other animals.</p> + +<p><i>Haeckel</i>, in 1872, found the same in the +Sponges. He stated that these two germinal +layers occur in all animals, except in the +Protozoa; and that they are homologous, +or equivalent, in all the groups of animals, +from the Sponges up to Man. In 1873, in +his 'Gastræa-theorie,' he explained the +phylogenetic significance, and tried to show +the homology, of the four secondary germinal +layers.</p> + +<p><span class="pagenum"><a name="Page_117" id="Page_117">[Pg 117]</a></span></p> + +<hr class="chap"/> +<div class="chapter-beginning"/> +<h2>FACTORS OF EVOLUTION.</h2> + + +<p>An organism, as living matter, does not +stand in opposition to, or outside of, the rest +of the world. It is part of the world. It +receives matter from its surroundings, and +gives some back; therefore it is influenced +by its surroundings. It is acted upon, and +it reacts upon the latter, and if these change +(and they are nowhere and never strictly the +same) the organism also <i>varies</i>. It <i>adapts</i> +itself, and if it does not, or, rather, cannot, +do so, it dies, because it is unfit to live in the +world, or, rather, in those particular surroundings +and conditions in which it happens to be. +That organism which yields most easily, accommodates +itself most quickly, has the best +chance of existence—<i>survival of the fittest</i>.<span class="pagenum"><a name="Page_118" id="Page_118">[Pg 118]</a></span> +'Fitness' in this case does not mean fitness +to live, but rather a particular condition which +happens to fit into the new circumstances.</p> + +<p>Adaptation and variation are simultaneous: +they are fundamentally the same. If there +were no adaptability and no variability, +those simplest of organisms which we suppose +to have sprung into existence in the +pre-Cambrian period would long ago have +ceased to exist.</p> + +<p>It is the physiological momentum which +models the organism, and, by causing its +adaptations, has produced its organs by +change of function. Gegenbaur illustrates +this most important fundamental truth by +an excellent example. Suppose that, in an +absolutely simple organism, all the parts of +its exterior are under the same functional +conditions, so that each part of the surface +can take in food, and that this is digested, +assimilated, in the interior. There is, in +this condition, not yet any definite organ. +If this organism sinks to the bottom and<span class="pagenum"><a name="Page_119" id="Page_119">[Pg 119]</a></span> +becomes sessile, this part is excluded from +taking in nourishing matter, while the +opposite surface alone remains, or becomes +more, fit for this function. Thus, a simple +variation and adaptation has been produced, +and if the same organism continues in this +position, its bottom cells will estrange themselves +from their original function, while +those on the top will convey the food into +the interior, where a cavity will be formed, +ultimately with a permanent opening, the +primitive gut and mouth, both very different +from the 'foot.'</p> + +<p>Thus, by adaptation and variation the +organism acquires new functions, organs, +features, and it gives up and eventually loses +others. Its offspring is like it. Like produces +like. This is the principle of <i>heredity</i>. +Adaptation, when going on generation after +generation on the same lines in the same +direction, becomes continuous, and has an +intensifying, <i>cumulative</i> effect. By always +weeding out from a flock of pigeons those birds<span class="pagenum"><a name="Page_120" id="Page_120">[Pg 120]</a></span> +which possess more dark feathers than the +rest, we ultimately produce an entirely white +race. We hurry on what Nature does slowly.</p> + +<p>The inheritance of acquired characters +becomes very obvious in the following +example: The Monera are the lowest living +organisms known; they consist of a mass of +protoplasm, and are still devoid of even a +nucleus. They multiply simply by division; +each half is like the other, and like the parent +(which by this process has ceased to exist), +except that each is smaller and has to grow. +A certain Moneron, <i>Protomyxa aurantiaca</i>, +is orange-coloured, and its offspring is from +the beginning of the same colour, and this +colour has been acquired by that kind of +Monera-like protoplasm which thereby has +become the species called Aurantiaca. We +have no reason for assuming that there +existed from the beginning of life not only +colourless, but also red, orange, and other +kinds of protoplasm. In these simplest of +organisms the whole process of heredity<span class="pagenum"><a name="Page_121" id="Page_121">[Pg 121]</a></span> +seems very obvious; but in the higher ones, +in those which propagate by eggs, the +problem is infinitely more complicated. It +is true that the egg is, strictly, nothing but a +small part of the parental organism, and we +know from everyday experience that this +single egg-cell has in it all the attributes and +characteristics of the parent; but these attributes +and characteristics make their appearance +successively, just as the egg cell of a +chick has neither wings nor feathers, not +even a backbone, but develops these organs +because its parents have them.</p> + +<p>The theory that acquired characters are +hereditary has often been vigorously attacked; +but the champions of the negative position +have not given us anything satisfactory +instead. They question, also, the principle +of adaptation as a factor in Evolution, and +substitute 'variation,' coupled with 'natural +selection.'</p> + +<p>They point to Darwin's argument: (1) It +is a fact that animals and plants produce a<span class="pagenum"><a name="Page_122" id="Page_122">[Pg 122]</a></span> +much greater number of young than in their +turn grow up to propagate the race; (2) no +two of the frequently many individuals of +the same breed are exactly alike, although +the differences may be hidden to our perception +(this is quite true, because no two +entities can live in absolutely the same place +and conditions); (3) through heredity the +offspring takes over the faculties and features +of the parents; (4) what decides which of +the many individuals (each one possessing +some aberration or variation) are to live and +to propagate the race?—obviously those +individual variations which happen to make +the lucky possessors most fit for the struggle +for life.</p> + +<p>So far, well; but the 'Neo-Darwinians' +imagine that 'adaptation' is not the cause, but +the result, the effect, of the formation of +species. According to them, the species are +neither adapted by, nor do they adapt themselves +to, their surroundings. Adaptation is to +them an accomplished fact, a condition which a<span class="pagenum"><a name="Page_123" id="Page_123">[Pg 123]</a></span> +species happens to be in because its particular +variation is the one which, to the exclusion +of others, suits or fits into its surroundings. +Such a view simply takes variation for +granted, and stipulates it as a something +<i>a priori</i>, without raising the further necessary +question, why there should be any +variations at all. Why, indeed, unless they +are caused by external influences? Haeckel +elucidated this by the conception of adaptation +as explained in the foregoing pages.</p> + +<p>These and kindred speculations have produced +some rather curious discussions, which +not infrequently end in conundrums. If we +speak of a case of adaptation as a condition, a +fact, we easily run the risk of getting into confusion +about cause and effect. For example: Is +the stag swift because he has long and slender +legs, or are his legs long because he is swift? +In reality, swiftness and length of legs are +cause and effect in one. His legs have been +so modified as to make him swift, because he +has put them continuously to whatever was<span class="pagenum"><a name="Page_124" id="Page_124">[Pg 124]</a></span> +his full speed, which in his thick-footed +ancestors was probably a very slow one. +The above question reads, therefore, more +sensibly as follows: Has the stag become +swift because his legs have become long and +slender, or have his legs become long and +slender because he has attained swiftness? +Now, we see that both halves of the double +question are practically the same and instantly +suggest the answer.</p> + +<p>A fundamental difference between artificial +machines and living organisms is that the +former are worn out by use, while the latter +not only repair the loss caused by use, but are +also stimulated to further increase. On the +other hand, organs which are not put into +function, or are not used, <i>degenerate</i>. The +various cells of the organ react upon external +stimuli by increased activity. Why this should +be so is another question—perhaps because +those which do not would soon be not fit to +survive. Each cell has a function; the more +specialized the more intense it is. Every<span class="pagenum"><a name="Page_125" id="Page_125">[Pg 125]</a></span> +external stimulus, every contact with the +outer surroundings, is an insult, necessarily +of detrimental effect, as it disturbs the equilibrium +of the cell body. It must, therefore, +be of advantage to the cells' well-being to +return as soon as possible to the <i>status quo +ante</i>, and this can only be done by increased +activity.</p> + +<p>In the present state of our knowledge, +we can approach only the simplest cases of +acquisition of characteristics. Mostly they +are so complicated, subject to so many unthought-of +conditions, that we do not know +from which end to approach the problem. +Frequently the supposed use of certain +obvious features is the merest guesswork. +This applies especially to features to which +we are not accustomed (although wrongly +so) to assign a function—for example, coloration. +A green tree-frog will with predilection +rest on green leaves. The advantages +of concealment are obvious, and in this case +he 'adapts himself' to the surroundings by<span class="pagenum"><a name="Page_126" id="Page_126">[Pg 126]</a></span> +making for green localities: if he did not +he would be eaten up sooner than his more +circumspect comrades. But this making for, +and sitting in, the green has not <i>necessarily</i> +made him of that colour. Extreme advocates +of one view would argue as follows: +Once upon a time there were among the +offspring of ancestral tree-frogs some which, +among other colours, exhibited green, not +much, perhaps not even perceptible to our +eyes. The occurrence of this colour, according +to them, was spontaneous, a freak—as if +in reality there were anything spontaneous +in the sense of being causeless. The +descendants of these more greenish creatures, +provided they did not pair with frogs of the +ordinary set, became still greener (by accumulative +inheritance), and so on, until the green +was pronounced sufficient to be of advantage +when competition could set in.</p> + +<p>With this view there is always the difficulty +of understanding how the initial very +small changes can be useful, unless we have<span class="pagenum"><a name="Page_127" id="Page_127">[Pg 127]</a></span> +to deal with extremely simple organisms. Is +it likely in the case of our frogs that an +almost imperceptible variation in colour makes +them more fit to live? We have to assume +that 'luck' or chance kept them for generations +out of harm's reach, until the accumulation +of green, hitherto quite ineffective, +neither harmful nor useful, became strong +enough to be effective. Such cases undoubtedly +happen.</p> + +<p>But we can also argue out this problem +in a somewhat different way, which goes +nearer to the root of the whole process. The +original slight, imperceptible change in pigmentation +is not a spontaneous freak; it was +caused by the direct influence of the surroundings +in which the particular frogs +happened to live, be this factor light or +temperature or food. Thus it stands to +reason that the offspring, living under similar +conditions, will be acted upon in the same +way. That factor which has added green to +the parents will add green to the children,<span class="pagenum"><a name="Page_128" id="Page_128">[Pg 128]</a></span> +until by accumulative inheritance a more +decidedly green race is produced.</p> + +<p>The offspring of green plants do not +become green when grown in the dark; the +young plants inherit not the green, but the +capacity of becoming green when acted upon +by sunlight. This as an instance of direct +influence of the surroundings on a substance +(chlorophyll), which has not yet performed a +function. But the kittens of a pair of black +cats produce black hair before they are born, +and we have no reason to doubt that the +black pigment in their tegumentary structures +is ultimately referable to the action of the +sunlight. In many instances creatures living +for generations in darkness become white, +pigmentless, and they regain it when exposed +to light. For example, the white, colourless +Proteus from the caves of Adelsberg becomes +clouded grey, and ultimately jet black, when +kept in a tank whence light is not strictly +excluded.</p> + +<p>Blindness is a very general characteristic<span class="pagenum"><a name="Page_129" id="Page_129">[Pg 129]</a></span> +of creatures which dwell in darkness. There +are all stages between total blindness and +weak eyes. Now, do these blind creatures +live in darkness because they are blind, or +have they become first weak-eyed and then +blind because of the continuous disuse of +their eyes? The former explanation has +actually been suggested! Individuals not +smitten, but spontaneously, as a freak, born +with sore eyes, have crept into the darkness +for relief and have produced a blind race! +To carry such a notion to the bitter end leads +to absurdities. Anyhow, it is not understandable +where the benefit of losing the +eyesight arises. It can be explained only +by continued disuse: witness <i>Spalax typhlus</i>, +the blind mole, and, above all, the Endoparasites.</p> + +<p>Let us now take an example to explain the +influence of a tangible external stimulus. +Repeated pressure produces callosities. +Although they are not exactly beneficial +in the shape of corns on our toes, they are<span class="pagenum"><a name="Page_130" id="Page_130">[Pg 130]</a></span> +so on our hands. At any rate, the morphologist +can trace the development of the +footpads, nails, hoofs, and horns, step by +step from small beginnings. The cells of +the Malpighian stratum, of the inner, active +portion of our epidermis, are excited to extra +activity, and by continually producing more +horn cells than peel off the surface of the +skin in the normal process of wear and tear +cause the formation of the pad. It need +scarcely be mentioned that hypertrophic +growths are not necessarily useful; they are +often harmful, and in that case pathological.</p> + +<p>Lastly, a few words about the very difficult +question of <i>teleology</i>. In trying to explain +Evolution in a mechanical—sometimes called +monistic, but in reality natural—way, we +exclude anything like a set purpose, a goal, +or ideal, a final condition which the organism +strives to attain. Unknown, however, to +many morphologists, especially embryologists, +their writings are full of this teleological +notion. Indeed, there are many cases<span class="pagenum"><a name="Page_131" id="Page_131">[Pg 131]</a></span> +in which an organism becomes changed, and +quickly, too, in a way which cannot but be +called reasonable. It starts modifications, be +they outgrowths, alterations in shape or colour, +or the making good of injuries received, +which by 'short-cuts' produce the only +advantageous result that can reasonably +satisfy the new requirement or altered circumstances.</p> + +<p>Trees growing in precarious positions, +after part of the supporting rock has slipped +away, throw out new roots, and rearrange some +of the old ones in the only way which could +save the tree. In animals which have lost part +of a limb the wound closes up, and what is left +is turned into a serviceable stump—for +example, in water-tortoises (creatures in which +reproduction of lost limbs does not happen). +In frogs and newts the lost part is reproduced, +not correctly, but in a good semblance. +Tortoises which have had their shell smashed +can throw off an astonishingly large portion +and renew the bone as well as the over<span class="pagenum"><a name="Page_132" id="Page_132">[Pg 132]</a></span>lapping +scutes; but this mending is not neatly +done. It serves the requirement, but it is +patchwork; the new shell is such as no +tortoise ever possessed before.</p> + +<p>Mammals transported into colder countries, +or subjected to continued exposure, grow a +thicker coat; and the same kind of tree +which in a sheltered valley is tall, large-leaved, +and soft-wooded, assumes a very +different aspect, although perhaps growing +into a healthy specimen, when planted on a +wind-exposed hill.</p> + +<p>There is no room, or, rather, no time, to +apply to these cases the principle of many +variations or the long-continued accumulation +of infinitely small changes. The thing is to +be done quickly, or not at all. Nor can we +explain the mending of a wound, which +implies an activity of countless cells, simply +as a case of, or similar to, the reproduction +of a lost part; against such an +explanation militates the almost absolute +unlikelihood of that precise injury having<span class="pagenum"><a name="Page_133" id="Page_133">[Pg 133]</a></span> +happened before to any of the creature's +ancestors.</p> + +<p>Still, I think we are brought near the solution +of the mystery by such considerations. +We see no difficulty in the regeneration of a +few cells, or in the making good of the disturbance +suffered by one of the most simple +organisms; but we become suspicious when +we see that countless cells, not of one kind, +but of the most varied tissues and parts of +the body, make common cause in remedying +a defect in a serviceable way.</p> + +<p>We must assume that since the beginning +of life organisms have been subjected to +countless insults. We can scarcely speak of +a wound in an Amæba; but these insults +have always been made good, and whenever +this was not the case, that particular organism +came to an end. As these organisms developed +into more complicated ones, the +possible insults became more serious, more +complicated; and the organisms took adaptive +measures so as to be superior to them. This<span class="pagenum"><a name="Page_134" id="Page_134">[Pg 134]</a></span> +action, I have no hesitation in declaring, +became by heredity a habit. The whole +creature became so thoroughly 'imbued' (for +want of a better word) with the finding of +ways and means for meeting sudden, serious +conditions, that it now acts directly, and +produces by a short-cut, with the least amount +of time and with the smallest possible waste +of material, that which meets the occasion, +thereby saving the life of the individual and +that of the race. This we cannot but call +reasonable and to the purpose, although it is +all carried out by <i>causæ efficientes</i> without +there being any <i>causæ finales</i>.</p> + +<p><span class="pagenum"><a name="Page_135" id="Page_135">[Pg 135]</a></span></p> + +<hr class="chap"/> +<div class="chapter-beginning"/> +<h2>GEOLOGICAL TIME AND EVOLUTION.</h2> + + +<p>One million years is a stretch of time beyond +our conception. We can arrive at a more or +less adequate understanding of what a million +individuals or concrete things means. Several +Continental nations can put more than a +million men into the field. We can gaze at +a building which contains as many bricks; +and we know that our own body is composed +of millions of millions of cells. No +such help applies to time, because that itself +is an entirely relative, abstract conception. +We can imagine what one hundred years are +like—a span of time seemingly short to the +hale and hearty octogenarian, enormous to +the child, totally inapplicable to certain<span class="pagenum"><a name="Page_136" id="Page_136">[Pg 136]</a></span> +animals whose whole life is crowded into one +single day.</p> + +<p>Astronomers have long ceased to reckon +distances by miles or any other understandable +unit. They express the distances +between us and the stars and nebulæ by +'years of light.' Try to imagine a unit of +length equal to that which is passed through +by light (186,000 miles per second) in one +year. Not so very long ago the enormous +distances resulting from astronomical calculations +were looked upon as the most serious +objection to the correctness of the astronomers' +views as to the distances which separate our +globe from the nearest fixed stars. We have +not yet accustomed ourselves to reckoning +time by some similar broadly-conceived +standard—say æons of so many thousand +years each.</p> + +<p>Unfortunately, we possess no data whatever +for calculating the age of the successive +geological strata. Thanks to Lyell, the +theory of violent universal cataclysms has<span class="pagenum"><a name="Page_137" id="Page_137">[Pg 137]</a></span> +been done away with. It is more probable +that the same agencies have acted which are +now changing the aspect of the globe; and +these changes are slow, as far as we know +them—at least, as far as the formation of +sedimentary strata is concerned, and these +alone we have to deal with. Various calculations +have been made, based upon the +denudation of the mountains, the filling up of +the valleys by the débris, the formation of +deltas, etc. The results give enormous +stretches of time, but all of them unsatisfactory, +because the methods are so very local in +their application.</p> + +<p>The least objectionable attempt is that +which, based upon astronomical calculations, +tried to fix the height of the last Glacial +epoch<a name="FNanchor_27_27" id="FNanchor_27_27"></a><a href="#Footnote_27_27" class="fnanchor">[27]</a> at about 200,000 years ago, and +asserted that since its beginning in the +Pliocene epoch as many as 270,000 years +have elapsed. The duration of the whole<span class="pagenum"><a name="Page_138" id="Page_138">[Pg 138]</a></span> +Tertiary period has by the same authorities +been fixed approximately at 3,000,000 to +4,000,000 years. Beyond this we cannot venture +without the wildest speculation; but we +know to a certain extent the thickness of the +various sedimentary strata, which amount in +all to from 100,000 to 175,000 feet—on the +average perhaps 130,000 feet, or about twenty +miles.</p> + +<p>Unless we prefer giving up all attempt +at calculation as absolutely hopeless, and +thus resign the whole problem, we must at +least try to arrive at some results, and then +see if these cannot reasonably be made use of.</p> + +<p>Neither geologist nor physicist, and no +zoologist, would accept the suggestion that +these 130,000 feet of stratified rocks have +been deposited within only as many years, +although the average rate of deposit would +in that case be not more than 1 foot per +year. On the other hand, an indignant protest +is raised against the assumption of +1,000,000,000 years.</p> + +<p><span class="pagenum"><a name="Page_139" id="Page_139">[Pg 139]</a></span></p> + +<p>Lord Kelvin<a name="FNanchor_28_28" id="FNanchor_28_28"></a><a href="#Footnote_28_28" class="fnanchor">[28]</a> has come to the conclusion +(from data which various other authorities +regard as very unsatisfactory) that not +much more than 100,000,000 years can have +elapsed since the molten globe acquired a +consolidated crust. Further time must have +passed before the surface had become stable +and cool enough to allow the temperature of +the collecting oceans to fall below boiling-point, +and it is obvious that life cannot +possibly have begun until after this had +happened.</p> + +<p>Wallace, in his 'Island Life,' by making +use of Professor A. Geikie's results as to the +rate of denudation of matter by rivers from +the area of their basins, and estimating the +average rate of deposition, concludes that +'the time required to produce this thickness +of rock [Professor Haughton's maximum of +177,000 feet] at the present rate of denudation +and deposition is only 28,000,000 years.'<span class="pagenum"><a name="Page_140" id="Page_140">[Pg 140]</a></span> +Our lower assumption of 130,000 feet thickness +would give only 20,000,000 years—a +rate of 1 foot in 154 years.</p> + +<p>Again, if we prefer round numbers to start +with, we have only to assume that the age of +the whole Tertiary period, with its 3,000 feet +thickness, is 3,000,000 years (<i>i.e.</i>, 1,000 feet +in 1,000,000 years, or 1 foot in 1,000 years, +surely an excessively slow rate); then +130,000,000 years would bring us to the +bottom of the Laurentian or pre-Cambrian +deposits. Of course, it is a pure assumption +that the same rate of destruction and sedimentation +applies to the whole of the strata; +but we know nothing to the contrary, especially +if we consider the average periods, the +quick periods of extra activity, taken with the +slow periods or those of standstill.</p> + +<p>Dana estimated the length of the whole +Tertiary period at one-fifteenth of the Mesozoic +and Palæozoic combined. If we take +the duration of the Tertiary period, as before, +as 3,000,000 to 4,000,000 years, the total<span class="pagenum"><a name="Page_141" id="Page_141">[Pg 141]</a></span> +will amount to from 45,000,000 to 60,000,000 +years.</p> + +<p>Lastly, Walcott<a name="FNanchor_29_29" id="FNanchor_29_29"></a><a href="#Footnote_29_29" class="fnanchor">[29]</a> has estimated the duration +of the Palæozoic, Mesozoic, and Cænozoic +or Tertiary epochs at about 17,000,000, +7,000,000 and 3,000,000 years respectively, +giving 27,700,000 years from the beginning +of the Cambrian; and Williams<a name="FNanchor_30_30" id="FNanchor_30_30"></a><a href="#Footnote_30_30" class="fnanchor">[30]</a> has calculated +the relative duration of the smaller +epochs. See the table on p. 149.</p> + +<p>The results of all these calculations fall +surprisingly well within the limits of Lord +Kelvin's allowance. Of course they are +based upon assumptions, but none of them +is inherently unreasonable; and it was my +purpose to draw attention to the surprising +coincidence in the closeness of these results, +perhaps too good to be true. Such calculations +are considered close enough if they +range within a few multiples of each other.</p> + +<p><span class="pagenum"><a name="Page_142" id="Page_142">[Pg 142]</a></span></p> +<p>Zoologists have fallen into the habit of +requiring enormous lengths of time for the +evolution of the animal kingdom. We know +that Evolution is at best a slow process, and +the conception of the changes necessary to +evolve man from monkey-like creatures, these +from the lowest imaginary mammals, these +from some reptilian stock, thence descending +to Dipnoan fish-like creatures, and so on +back into Invertebrata, down to the simple +Monera—this conception is indeed gigantic. +Innumerable, almost endless, slow changes +require seemingly unlimited time, and as time +is endless, why not draw upon it <i>ad libitum</i>?</p> + +<p>Huxley pointed out that it took nearly the +whole of the Tertiary epoch to produce the +horse out of the four-toed Eohippos, and +that, if we apply this rate to the rest of +its pedigree, enormous times would be required. +This is, however, a very misleading +statement, which necessitates considerable +reduction, in conformity with our increased +palæontological knowledge. Animals of the<span class="pagenum"><a name="Page_143" id="Page_143">[Pg 143]</a></span> +genus Equus—namely, Ungulata, with one +toe, and with a certain tooth pattern—from +the Upper Miocene of India are now known. +Moreover, it is not simply a question of the +gradual loss of the side-toes. The change +from the fox-sized little Eohippos and Hyracotherium, +so far as skull, teeth, vertebral +column, and limbs are concerned (about the +soft parts we know next to nothing), is a +very great one indeed.</p> + +<p>Elephants and mammoths seem to have +developed very rapidly. None are known +from Eocene strata; but towards the end +of the Miocene they had spread over Asia, +Europe, and North America, and that in +great numbers. The Eocene Amblypoda +are still so different that we hesitate to connect +them ancestrally with the elephants.</p> + +<p>The Pinnipedia (seals and walruses) are +strongly modified fissiped Carnivora, and have +existed since at least the Upper Miocene; +the transformation must have been accomplished +within the Miocene period.</p> + +<p><span class="pagenum"><a name="Page_144" id="Page_144">[Pg 144]</a></span></p> + +<p>We cannot shut our eyes to the fact that +various groups have from the time of their +first appearance burst out into an exuberant +growth of modifications in form, size, and +numbers, into all possible—and one might +almost say impossible—shapes; and they +have done this within comparatively short +periods, after which they have died out not +less rapidly. It seems almost as if these go-ahead +creatures had, by accepting every +possible modification and carrying the same +to the extreme, too quickly exhausted their +plasticity—which, after all, must have limits—thereby +becoming unable to meet successfully +the requirements of further changes in their +surroundings. The slowly developing groups, +keeping within main lines of Evolution, and +not being tempted into aberrant side-issues, +had, after all, a much better chance of onward +evolution.</p> + +<p>A good example of the former are the +Dinosaurs. We do not know their ancestors; +but we have here to deal only with their<span class="pagenum"><a name="Page_145" id="Page_145">[Pg 145]</a></span> +range of transformation. The oldest known +forms occur in the Upper Trias; they attain +their most stupendous development in the +Upper Jurassic and in the Wealden; and +they have died out with the Cretaceous epoch. +But already some of their earliest forms had +assumed bipedal gait, and the Oolitic Compsognathus +had developed almost bird-like hind-limbs.</p> + +<p>On the other hand, there are many +instances of extremely slow development—facts +which raise the difficult question of +'persistent types.' Are these due to a state of +perfection which cannot be improved upon? +Or are they due to a kind of morphological +consolidation (not necessarily specialization) +which can no longer yield easily, so that therefore +through changes in their surroundings +they may come to an end sooner than more +plastic groups?</p> + +<p>Struthio, the ostrich; Orycteropus, the +Cape ant-eater; Tapirus, and many others, +existed in the Miocene age practically as<span class="pagenum"><a name="Page_146" id="Page_146">[Pg 146]</a></span> +they are now; but pre-Pliocene dolphins, +cats, monkeys, stags, all belong to closely-allied +and well-defined 'genera,' but different +from the living forms.</p> + +<p>Alligators and crocodiles are known from +the Upper Chalk; Tomistoma since the +Miocene; Gavialis since the Pliocene.</p> + +<p>The oldest surviving reptile is Sphenodon, +the Hatteria of New Zealand, a fair representative +of what generalized reptiles of the +later Triassic period seem to have been like; +and to the same period belongs Ceratodus, +the Australian mud-fish, hitherto the oldest +known surviving genus of a very ancient and +low type so far as Vertebrata are concerned.</p> + +<p>Now let us see if the above estimates of +geological time are so utterly inapplicable to +animal evolution. On purpose we take one +of the lowest estimates, about 28,000,000 +years, and apportion them equally to the +various strata or epochs.</p> + +<p>The original owner of the famous Trinil +skull, a <i>Pithecanthropus erectus</i>, lived,<span class="pagenum"><a name="Page_147" id="Page_147">[Pg 147]</a></span> +according to some, in the Late Pliocene, +according to others in the Early Plistocene, +period—that is to say, somewhere about +the beginning of our last Glacial epoch, +some 270,000 years ago. Assuming that +he and his like reached puberty at sixteen +to twenty years of age, about 17,000 generations +would lie between him and ourselves, +or, to put it more forcibly, between +him and the lowest living human races—say +the Ceylonese Veddahs. Only 250 generations, +at twenty years, carry us back to +3000 <span class="smcap">B.C.</span> (<i>i.e.</i>, beyond the ken of history); and +if it be objected that the differences between +the oldest inhabitants of Egypt, the Naquada, +and the present Fellahin are very slight, +we are welcome to multiply these differences +sixty or seventy fold, in order to arrive at the +Pithecanthropus level. But these Naquada +had no metal implements, and there cannot be +the slightest doubt that the development of +the human race went on by leaps and bounds +after certain discoveries had been made—to<span class="pagenum"><a name="Page_148" id="Page_148">[Pg 148]</a></span> +wit, the use of implements and that of fire. +That creature which first took up a stone or +a branch and wielded it thereby got such an +enormous advantage over his fellow-creatures +that his mental and bodily development went +on apace. The same applies to the improvement +of speech. We assume the single, +monophyletic origin of mankind at one place, +in one district; and the differences between +some of the races of man are great enough +to constitute what we might call species. +Compare the Venus of Milo, that noble expression +of the ancient Greeks' notion of +female beauty, with the 'products of art' of +the Veddahs or the dwarfs of Central Africa, +or think of the beau-idéal which a Michael +Angelo could possibly have evolved if he had +never seen any but such people.</p> + +<p><span class="pagenum"><a name="Page_149" id="Page_149">[Pg 149]</a></span></p> + +<div style="line-height:90%"> +<table id="tae" summary="time" cellpadding="1" cellspacing="0" rules="cols" frame="box"> +<tr style="border:1px solid black;"> + <td class="tdc">I.</td> + <td class="tdc">II.</td> + <td class="tdc" >III.</td> + <td class="tdc" >IV.</td> + <td class="tdc" >V.</td> + <td class="tdc" >VII.</td> + <td class="tdc">VII.</td> +</tr> +<tr> + <td class="tdl">Recent</td> + <td class="tdl">}</td> + <td class="tdl" ></td> + <td class="tdl" ></td> + <td class="tdl" >Adam and Eve</td> + <td class="tdr" ></td> + <td class="tdr">250</td> +</tr> +<tr> + <td class="tdl"> Plistocene</td> + <td class="tdl">} 5</td> + <td class="tdl" >}</td> + <td class="tdl" >}</td> + <td class="tdl" >Man, contemp-</td> + <td class="tdr" ></td> + <td class="tdr">3,500</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" >} 270,000</td> + <td class="tdl" > orary with Reindeer</td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl"></td> + <td class="tdl" >}</td> + <td class="tdl" >}</td> + <td class="tdl" > in France</td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Pliocene -</td> + <td class="tdl">}</td> + <td class="tdl" >} 3,000,000</td> + <td class="tdl" ></td> + <td class="tdl" >Pithecanthropus</td> + <td class="tdr" >16</td> + <td class="tdr">17.000</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" >} 600,000</td> + <td class="tdl" > erectus</td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Miocene -</td> + <td class="tdl">}10</td> + <td class="tdl" >}</td> + <td class="tdl" ></td> + <td class="tdl" >Anthropoid</td> + <td class="tdr" >10</td> + <td class="tdr">60,000</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">}</td> + <td class="tdl">}</td> + <td class="tdl" >} 2,100,000</td> + <td class="tdl" > Apes</td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Eocene -</td> + <td class="tdl">}</td> + <td class="tdl" ></td> + <td class="tdl" >}</td> + <td class="tdl" >Lemurs</td> + <td class="tdr" >5</td> + <td class="tdr">420,000</td> +</tr> +<tr> + <td class="tdl">Cretaceous -</td> + <td class="tdl"> 10</td> + <td class="tdl" >}</td> + <td class="tdl" > 3,600,000</td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Jurassic -</td> + <td class="tdl"> 5</td> + <td class="tdl" >}</td> + <td class="tdl" > 1,800,000</td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Rhætic -</td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" >}</td> + <td class="tdl" >Prototheria, or</td> + <td class="tdr" >3</td> + <td class="tdr"> 1,800,000</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" >}</td> + <td class="tdl" > first Mammalia</td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">}</td> + <td class="tdl" >} 7,200,000</td> + <td class="tdl" >}</td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Keuper -</td> + <td class="tdl">} 5</td> + <td class="tdl" >}</td> + <td class="tdl" >}1,800,000</td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Muschelkalk -</td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" >}</td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">New Red</td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" >}</td> + <td class="tdl" >Theomorpha</td> + <td class="tdr" >4</td> + <td class="tdr">425,000</td> +</tr> +<tr> + <td class="tdl"> Sandstone </td> + <td class="tdl"></td> + <td class="tdl" ></td> + <td class="tdl" ></td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Magnesian</td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" >}</td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl"> Limestone</td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" >}</td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Lower Red</td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" >}</td> + <td class="tdl" >Proreptilia</td> + <td class="tdr" >4</td> + <td class="tdr">250,000</td> +</tr> +<tr> + <td class="tdl"> Sandstone</td> + <td class="tdl">}15</td> + <td class="tdl" >}</td> + <td class="tdl" >}4,000,000</td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Coal-measures</td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" >}</td> + <td class="tdl" >Eotetrapoda</td> + <td class="tdr" >4</td> + <td class="tdr">500,000</td> +</tr> +<tr> + <td class="tdl">Mountain</td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" >}</td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl"> Limestone</td> + <td class="tdl">}</td> + <td class="tdl" >}17,500,000</td> + <td class="tdl" >}</td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> + +<tr> + <td class="tdl">Devonian -</td> + <td class="tdl"> 15</td> + <td class="tdl" >}</td> + <td class="tdl" >4,000,000</td> + <td class="tdl" >Dipnoi and</td> + <td class="tdr" >5</td> + <td class="tdr">1,000,000</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl"></td> + <td class="tdl" >}</td> + <td class="tdl" ></td> + <td class="tdl" > Crossopterygii</td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Silurian -</td> + <td class="tdl"> 10</td> + <td class="tdl" >}</td> + <td class="tdl" >2,700,000</td> + <td class="tdl" >First fishlike</td> + <td class="tdr" >3</td> + <td class="tdr">900,000</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" ></td> + <td class="tdl" > creatures</td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Ordovician -</td> + <td class="tdl"> 10</td> + <td class="tdl" >}</td> + <td class="tdl" >2,700,000</td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Cambrian -</td> + <td class="tdl"> 15</td> + <td class="tdl" >}</td> + <td class="tdl" > 4,000,000</td> + <td class="tdl" >Sum total of</td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Laurentian -</td> + <td class="tdl"></td> + <td class="tdl" ></td> + <td class="tdl" ></td> + <td class="tdl" > generations</td> + <td class="tdr" ></td> + <td class="tdr">————</td> +</tr> +<tr> + <td class="tdl">Archean or</td> + <td class="tdl"></td> + <td class="tdl" ></td> + <td class="tdl" ></td> + <td class="tdl" > (about)</td> + <td class="tdr" ></td> + <td class="tdr">5,375,000</td> +</tr> +<tr> + <td class="tdl"> Metamorphic</td> + <td class="tdl"></td> + <td class="tdl" ></td> + <td class="tdl" ></td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +</table> +</div> +<p><span class="pagenum"><a name="Page_150" id="Page_150">[Pg 150]</a></span></p> + +<p><span class="smcap">Explanation of the Table on p. 149.</span></p> + +<blockquote> + +<p>Column I. contains the names of the successive sedimentary +strata.</p> + +<p> " II. contains the percentage of the duration of the +various epochs, according to <i>Williams</i>, the +time from the Cambrian until recent times +being taken as 100.</p> + +<p> " III. gives the estimated duration in years of the +Palæozoic, Mesozoic, and Cænozoic periods, +according to <i>Walcott</i>.</p> + +<p> " IV. gives in years the duration of the various +smaller epochs, as computed from Walcott and +Williams' statements.</p> + +<p> " V. Representatives of stages of the ancestral line of +man. The names stand in the level of the +stratum in which they have made their first +appearance.</p> + +<p> " VI. contains the number of years which, in the present +calculation, have been assumed necessary for +the animal to reach puberty.</p> + +<p> " VII. contains the number of generations which can +have elapsed from stage to stage. For example, +60,000 generations separate the earliest known +anthropoid apes from Pithecanthropus.</p> +</blockquote> + +<p>Let us follow the descent of man further +back. The next stage, reckoning backwards, +is that from Pithecanthropus to <i>bonâ-fide</i> +anthropoid apes. They are represented in +the Miocene by various genera—<i>e.g.</i>, Pliopithecus +and Dryopithecus. According to +Croll and Wallace, 850,000 years ago carry us<span class="pagenum"><a name="Page_151" id="Page_151">[Pg 151]</a></span> +into the Miocene epoch. Assuming that +these apes lived about 600,000 years before +Pithecanthropus, namely, in the later half of +the Miocene, and taking puberty at ten years +of age, a high estimate, we get not less than +60,000 generations.</p> + +<p>2. From Apes back to lowest Lemurs in +the lowest Eocene. The date of Eocene +being fixed at 3,000,000, we have about +2,100,000 years for this stage; assuming as +much as five years for puberty, this results in +420,000 generations.</p> + +<p>3. From Lemures to Prototheria. The +earliest known mammalian remains come +from the Rhætic, or top formation of the +Triassic epoch; allowing for the Rhætic +only 100,000 years, we have to add the +whole of the Jurassic and Cretaceous, in all +about 5,500,000 years. Assuming three +years for a generation, we get 1,800,000 +generations.</p> + +<p>4. From Prototheria to something like the +Theromorpha at the bottom of the Triassic<span class="pagenum"><a name="Page_152" id="Page_152">[Pg 152]</a></span> +strata. A duration of 1,700,000 years divided +by four gives 425,000 generations.</p> + +<p>5. From Theromorpha to Proreptilia, +represented by Eryops and Cricotus from +the Lower Permian of Texas. Allowing +1,000,000 years, each generation at four +years, we obtain 250,000 generations.</p> + +<p>6. From Proreptilia to Eotetrapoda, the +first terrestrial Vertebrata, represented by +something like the Stegocephali, the earliest +of which are known from the Coal-measures. +Assuming them to have come into existence +at the bottom of the Coal-measures, for the +duration of which we may guess 2,000,000 +years, we get, with four years' allowance for +puberty, 500,000 generations.</p> + +<p>7. From Eotetrapoda to a not yet separated +or differentiated group of Crossopterygian +and Dipnoan fishes, both of which +are known from Devonian strata. The +duration of the latter has been computed at +4,000,000 years, which, with 1,000,000 for +the Mountain Limestone formation, gives us<span class="pagenum"><a name="Page_153" id="Page_153">[Pg 153]</a></span> +5,000,000 for this stage. Assuming, for the +sake of round numbers, as much as five +years for a generation, we get 1,000,000 +generations.</p> + +<p>8. Earliest stage, down to the first fish-like +creatures. Teeth and spines indicating the +existence of fishes are known from the Upper +Silurian. By carrying the earliest fishes down +to the bottom of the Silurian, with 2,700,000 +years' duration, and allowing three years for +attaining puberty, the calculation results in +900,000 generations.</p> + +<p>Further back we cannot go. We do not +know of any Vertebrate remains from the +Ordovician and Cambrian, which together +represent 6,700,000 years, enough for at least +half as many generations of Prochordate +creatures. The pre-Cambrian or Laurentian +epoch lies quite beyond the reach of calculation, +nor have we any trustworthy fossil +remains of living matter from these strata, to +which, however, Haeckel and others refer the +first beginnings of life.</p> + +<p><span class="pagenum"><a name="Page_154" id="Page_154">[Pg 154]</a></span></p> + +<p>All the above calculations are, of course, +only approximate. What we do know is +the existence of representatives of the stages, +our proofs being the fossils; but when we refer +the origin of the Eotetrapoda, for example, to +the bottom and not somewhere to the middle +of the Coal-measures, we are guessing +merely. Alterations in the levels assumed +for the various stage-representatives will, of +course, alter the result of the number of +generations; but the leading idea, as a +whole, is not thereby upset. The fact +remains that in the Upper Silurian we have +fishes; from the Coal-measures onwards, fishes +and Amphibia; since the Permian, fishes, +Amphibia, and reptiles; since the end of the +Trias these three classes and the Mammalia; +and lastly, at least since the Plistocene, man +himself. If Evolution is true at all, the +transformation from early fish-like creatures +to man has come about within these epochs. +Being able to assign a time of duration to +each of them, with an approximate total of<span class="pagenum"><a name="Page_155" id="Page_155">[Pg 155]</a></span> +21,000,000 years, we are also able to put +the whole ancestral series to a test by expressing +each great stage in generations. The +result is very satisfactory. The whole enormous +stretch from the lowest fish-like creatures +to man has been resolved into more +than 5,000,000 successive generations, and +each of these means a little step forwards in +onward Evolution.</p> + +<p>Nothing is to be gained for the understanding +of our problem of Evolution if we +multiply this enormous number of generations +by ten or any other multiple. We +are not able to conceive changes so small +as those which necessarily have existed +between Pithecanthropus and man if the +whole striking difference is analysed into +17,000 steps. Every one of these stages in +the modifications of the muscles, the skeletal +framework, increase of brain, shortening of +the trunk, lengthening of the legs, improvement +of the hands, loss of the hairy coat, etc., +is truly microscopical, imperceptible, just as<span class="pagenum"><a name="Page_156" id="Page_156">[Pg 156]</a></span> +the Evolutionist imagines the whole process +to have been. Again, where is the difficulty +implied by the change from an air-breathing, +in many structural points half-amphibian, fish +into a primitive land-crawling four-footed +creature, if we are allowed to resolve the +transformation into 1,000,000 stages? So far +from there being any difficulty, rather does it +appear questionable if so many infinitely small +changes have been necessary to bring about +this result.</p> + +<p>One thousand years make apparently no +difference in the evolution of animals, nor +does one second change the aspect of the +hands on the face of a clock, nor did Julius +Cæsar's commission of scientific men appreciate +the error of about eleven minutes in +the length of the year beyond its real value; +but now the Russians are, owing to this +neglect, nearly two weeks behind the civilized +nations.</p> + + +<p class="center">THE END.<br /> + +<small>BILLING AND SONS, PRINTERS, GUILDFORD.</small></p> + +<p><span class="pagenum"><a name="Page_157" id="Page_157">[Pg 157]</a></span></p> +<hr class="chap"/> +<div class="chapter-beginning"/> +<p class="center">By PROFESSOR ERNST HAECKEL</p> + +<p class="center"><big>MONISM</big>;<br /> +<small>OR</small>,<br /> +The Confession of Faith of a Man of Science.</p> + +<p class="center"> Translated from the German by J. D. F. GILCHRIST.</p> + +<p class="center"><i>Crown 8vo., cloth. Price 1s. 6d. net.</i> +</p> + +<p>'We may readily admit that Professor Haeckel has stated his case +with the clearness and courage which we should expect of him, and +that his lecture may be regarded as a fair and authoritative statement +of the views now held by a large number of scientifically educated +people.'—<i>Times.</i></p> + +<p>'The Monism, which is the substance of his faith, is thus defined by +him: "Our conviction that there lives one spirit in all things, and that +the whole cognizable world is constituted, and has been developed, in +accordance with one common fundamental law." As the confession of +a distinguished man of science, this little work deserves to be read.'—<i>North +British Daily Mail.</i></p> + +<p>'This "Confession of Faith" was delivered by the great German +scientist, its author, as an extemporaneous address at Altenburg rather +more than two years ago. There are, no doubt, a large number of +English readers who will welcome a translation, for this "connecting of +religion and science" has long troubled many earnest students of +modern science.'—<i>Publisher's Circular.</i></p> + +<p>'This is a little book of great daring, an example of the wild speculative +flights of one of the very ablest and greatest of our contemporary +men of science.'—<i>Aberdeen Free Press.</i></p> + +<p>'The address, whatever we may think of its conclusions, is, however, +most interesting reading, and is admirably done into English by the +translator.'—<i>Literary World.</i></p> + + +<p class="center">LONDON: ADAM & CHARLES BLACK, SOHO SQUARE.</p> + +<p><span class="pagenum"><a name="Page_158" id="Page_158">[Pg 158]</a></span></p> +<hr class="tb"/> + +<p class="center"> <i>Demy 8vo., price 7s. 6d. net.</i></p> + +<p class="center"><big>SOURCES OF THE APOSTOLIC CANONS.</big></p> + +<p class="center"> <i>With a Treatise on the Origin of the Readership and other Lower Orders.</i></p> + +<p class="center"> By Professor ADOLF HARNACK.</p> + +<p class="center"> Translated by LEONARD A. WHEATLEY.</p> + +<p class="center"> <i>With an Introductory Essay on the Organization of the Early Church + and the Evolution of the Reader.</i></p> + +<p class="center"> By the Rev. <span class="smcap">John Owen</span>, Author of 'Evenings with the Skeptics.' +</p> + +<p>'Dr. Adolf Harnack is at the present time undoubtedly the leading liberal +authority in Germany on matters connected with early Christian history.'—<i>The +Times.</i></p> + +<p>'Those who are interested in early Church history know how to prize anything +from the pen of Prof. Harnack. They will not be disappointed with the present +paper, in which, with his accustomed learning and acute criticism, he annotates +and comments upon the fragments of primitive church law which partly form the +basis of the Apostolic Canons.'—<i>British Weekly.</i></p> + +<p>'The wide circulation of this volume would be of the happiest augury for a +more scientific and worthy conception of the organization of the primitive +Church.'—Dr. <span class="smcap">Marcus Dods</span> in <i>The Bookman</i>.</p> + + +<hr class="tb"/> +<p class="center"> <i>Crown 8vo., cloth, price 1s. 6d. net.</i></p> + +<p class="center"><big>CHRISTIANITY AND HISTORY.</big></p> + +<p class="center"> By ADOLF HARNACK.</p> + +<p class="center"> Translated, with the Author's sanction, by THOMAS BAILEY + SAUNDERS, with an Introductory Note. +</p> + +<p>'It is highly interesting and full of thought. The short introductory note with +which Mr. Saunders prefaces it is valuable for its information and excellent in its +tone.'—<i>Athenæum.</i></p> + +<p>'A singularly able exposition and defence of Christianity, as seen in the newer +light, by one of the most learned and acute "evangelical" critics of Germany. +The essay is a masterly one.'—<i>Glasgow Herald.</i></p> + +<p>' ... We hope the lecture will be widely read.'—<i>Primitive Methodist +Quarterly Review.</i></p> + +<p>'The lecture itself is weighty in its every word, and should be read and re-read +by those desiring to have in a nutshell the central positions of modern Christianity.'—<i>Christian +World.</i></p> + +<p class="center">LONDON: ADAM & CHARLES BLACK, SOHO SQUARE.</p> +<p><span class="pagenum"><a name="Page_159" id="Page_159">[Pg 159]</a></span></p> +<hr class="tb"/> + +<p class="center"> <i>Third Edition. Crown 8vo., cloth, price 5s.</i></p> + +<p class="center"><big>SKETCH OF THE HISTORY OF ISRAEL AND JUDAH.</big></p> + +<p class="center"> By J. WELLHAUSEN,<br /> +<small>PROFESSOR AT MARBURG.</small> +</p> + +<p>'This work is now issued for the third time as an independent +treatise. It admirably epitomizes the subject, and exhibits on almost +every page evidences of Professor Wellhausen's profound study.'—<i>Publishers' +Circular.</i></p> + +<p>'We would only say that those who differ from his critical views +will yet do well to study them, and to read this history in which +he applies them. Its separate publication, in a handy form and at +a moderate price, makes it generally accessible.'—<i>North British +Daily Mail.</i></p> + +<p>'The publication in a separate form of Professor Wellhausen's +article in the "Encyclopædia Britannica" on "Israel" will be very +warmly welcomed by many readers.'—<i>Manchester Guardian.</i></p> + +<p>'We are very glad to welcome an edition of Professor Wellhausen's +"Sketch of the History of Israel and Judah" in a convenient +and handy form. This is the first time it has appeared in +a separate form. It is already known to students; it ought now +to become popular. It is based on the learned author's studies in +Hebrew literature and history, and, though not controversial in form, +it differs totally from orthodox presentations of the subject.'—<i>Westminster +Review.</i></p> + +<p>'A sketch which has created such widespread and profound +interest as this could not be kept in the pages of a voluminous +encyclopædia. Wellhausen's words necessarily have exceptional +importance, even in the esteem of those who differ from him <i>toto +cœlo</i>.'—<i>Baptist Magazine.</i></p> + +<p>'The profound scholarship of the author does not elevate his +writing above the interest of the general reader, and a vivid idea +of the involved Jewish history is obtainable from this volume.'—<i>Christian +Advocate.</i></p> + +<p class="center">LONDON: ADAM & CHARLES BLACK, SOHO SQUARE.</p> +<p><span class="pagenum"><a name="Page_160" id="Page_160">[Pg 160]</a></span></p> +<hr class="tb"/> +<p class="center"> <i>Demy 8vo., boards, price 3s. 6d. net.</i></p> + +<p class="center"><big>A CLASSIFICATION OF VERTEBRATA,</big><br /> + RECENT AND EXTINCT.</p> + +<p class="center"> With Diagnoses and Definitions, a Chapter on Geographical + Distribution, and an Etymological Index.</p> + +<p class="center"> By HANS GADOW, M.A., <span class="smcap">Ph.D.</span>, F.R.S.,</p> + +<p class="center"><small>STRICKLAND CURATOR AND LECTURER ON ZOOLOGY TO THE UNIVERSITY, + CAMBRIDGE.</small> +</p> + +<p>'At the end of his work Dr. Gadow adds a useful chapter on the geographical +distribution of the Vertebrata, with a table showing the approximate number of +the known recent species. He also gives a fanciful though striking calculation +to show how some groups are still in the ascendant, while others are distinctly +declining. The little volume is indeed a welcome addition to the biological +student's library, and it deserves the wide circulation which its author's eminence +is likely to ensure for it.'—<i>Natural Science.</i></p> + +<p>'It is a book, it need hardly be said, for the student; it is simply a list of the +principal sub-divisions of backboned animals, with just as much definition as is +needed. It may be regarded as an exceedingly concentrated extract of a full +text-book of the vertebrates.'—<i>Daily Chronicle.</i></p> + +<p class="center">LONDON: ADAM & CHARLES BLACK, SOHO SQUARE.</p> +<hr class="tb"/> + + +<p class="center"> <i>Demy 8vo., cloth, price 21s.</i></p> + +<p class="center"><big>IN NORTHERN SPAIN.</big></p> + +<p class="center"> By Dr. HANS GADOW, M.A., <span class="smcap">Ph.D.</span>, F.R.S.</p> + +<p class="center"> <i>Containing Map and 89 Illustrations.</i> +</p> + +<p>'Some years back "Wild Spain," one of the best books of its kind, made you +desirous of knowing more of the country. And Hans Gadow has deepened this +feeling in his excellent volume "In Northern Spain," and that to an enormous +extent. Dwelling at inn or farm, or in their own tent, they saw the country as +it has been seen but rarely, and they came to know the inhabitants as they can +be known in no other fashion.'—<i>Black and White.</i></p> + +<p>'To persons visiting the provinces with which the author deals, this book will +be invaluable, and will do more to point their attention to objects of interest than +existing guide-books of Spain, most of which are out of date.'—<i>The Field.</i></p> + +<p>'About the best book of European travel that has appeared these many +years.'—<i>Literary World.</i></p> + +<p class="center">LONDON: ADAM & CHARLES BLACK, SOHO SQUARE.</p> + + +<div class="footnotes"><h3>FOOTNOTES:</h3> + +<div class="footnote"> + +<p><a name="Footnote_1_1" id="Footnote_1_1"></a><a href="#FNanchor_1_1"><span class="label">[1]</span></a> See note,p.<a name="FNanchor_40" id="FNanchor_40"></a><a href="#Footnote_40">80.</a> </p> + +<p><a name="Footnote_2_2" id="Footnote_2_2"></a><a href="#FNanchor_2_2"><span class="label">[2]</span></a> See note, p.<a name="FNanchor_41" id="FNanchor_41"></a><a href="#Footnote_41">89.</a></p> + +<p><a name="Footnote_3_3" id="Footnote_3_3"></a><a href="#FNanchor_3_3"><span class="label">[3]</span></a> +See notes, p. <a name="FNanchor_42" id="FNanchor_42"></a><a href="#Footnote_42">102</a>, <a name="FNanchor_43" id="FNanchor_43"></a><a href="#Footnote_43">106</a>. </p> + +<p><a name="Footnote_5_5" id="Footnote_5_5"></a><a href="#FNanchor_5_5"><span class="label">[5]</span></a> +See note, p. <a name="FNanchor_44" id="FNanchor_44"></a><a href="#Footnote_44">80.</a> </p> + +<p><a name="Footnote_6_6" id="Footnote_6_6"></a><a href="#FNanchor_6_6"><span class="label">[6]</span></a> <i>Perfect</i>, in the sense of highest stage of evolution, may +seem a <i>petitio principii</i>. Leaving aside the consideration +that no living creature is absolutely perfect, in the sense that +its organization cannot become more efficient or proficient, +we have here to deal with relative perfection of the whole +organization. A fish or a snake is in its way more specialized +than a mammal; but specialization does not necessarily +mean height of development: it generally means life in a +comparatively narrow groove. The acts of giving birth and +nourishing the young with the mother's milk is a much +higher stage than the act of laying eggs and letting them +run their chance. The development of a hairy coat goes +along with heightened temperature of the blood, subsequent +greater independence of the surrounding temperature, and +increased steady activity of the brain and other nerve-centres. +The brain of the Mammalia, in its minute structure, +is much more complex. This rule applies to some of +the principal sense organs, chiefly the nose and the ear. +The skeleton, not so much as a whole as in the various bones +and joints, is more neatly finished, and built up more in +conformity with 'scientific principles,' than is the case even +with birds, in spite of their marvellous specialization. The +same is the case with the vascular system, notably the heart +and the veins, and with the excretory organs. In all of these +many imperfections, still to be found in the other classes, +have been corrected in Mammalia. The Primates take an +easy first by their hands, and among them the apes and man +himself by their brains.</p> + +<p><a name="Footnote_7_7" id="Footnote_7_7"></a><a href="#FNanchor_7_7"><span class="label">[7]</span></a> 'Die menschenähnlichen Affen und ihre Organisation +im Vergleich zur menschlichen.' 1883.</p> + +<p><a name="Footnote_8_8" id="Footnote_8_8"></a><a href="#FNanchor_8_8"><span class="label">[8]</span></a> G. Schwalbe, 'In wiefern ist die menschliche Ohrmuschel ein +rudimentäres Organ?'—In what Respects is the Human Outer Ear a +Rudimentary Organ? (<i>Archiv f. Anatomie und Physiologie</i>, 1889).</p> + +<p><a name="Footnote_9_9" id="Footnote_9_9"></a><a href="#FNanchor_9_9"><span class="label">[9]</span></a> Wiedersheim, 'Der Bau des Menschen als Zeugniss für +seine Vergangenheit.' Freiburg, 1888. Translated: 'The +Structure of Man an Index to his Past History.' London, +1895.</p> + +<p><a name="Footnote_10_10" id="Footnote_10_10"></a><a href="#FNanchor_10_10"><span class="label">[10]</span></a> <i>Pithecanthropus erectus.</i> 'Eine menschenähnliche +Uebergangsform aus Java' ('A Human-like Transitional +Form'). Batavia, 1894.</p> + +<p><a name="Footnote_11_11" id="Footnote_11_11"></a><a href="#FNanchor_11_11"><span class="label">[11]</span></a> On the day after the delivery of this address Dr. Dubois +exhibited the cranium of Pithecanthropus, from which he had +removed the stony matrix which filled the inside, in order to +examine the impression left by the cerebral convolutions. +He was able to show that they also are very human, and +more highly developed than those of the recent apes.</p> + +<p><a name="Footnote_12_12" id="Footnote_12_12"></a><a href="#FNanchor_12_12"><span class="label">[12]</span></a> L. Manouvier: 'Deuxième étude sur le Pithecanthropus erectus +comme précurseur présumé de l'homme.' (<i>Bulletins de la Soc. +d'Anthropologie de Paris</i>, 1895.)</p> + +<p><a name="Footnote_13_13" id="Footnote_13_13"></a><a href="#FNanchor_13_13"><span class="label">[13]</span></a> +See notes, p. <a name="FNanchor_45" id="FNanchor_45"></a><a href="#Footnote_45">93.</a> </p> + +<p><a name="Footnote_14_14" id="Footnote_14_14"></a><a href="#FNanchor_14_14"><span class="label">[14]</span></a> +See notes, p. <a name="FNanchor_46" id="FNanchor_46"></a><a href="#Footnote_46">87.</a> </p> + +<p><a name="Footnote_15_15" id="Footnote_15_15"></a><a href="#FNanchor_15_15"><span class="label">[15]</span></a> +</p> + +<blockquote> + +<p><span class="smcap">F. Ameghino</span>: 'Contribucion al conocimiento de los +mamÃferos de la república Argentina.' In <i>Actas de +la Academia nacional de Sciencias en Cordoba</i>, +1889.—Another article in <i>Revista Argentina de Historia +natural</i>. Buenos Aires, 1891. +</p> +<p> +<span class="smcap">A. Gaudry</span>: 'Animaux fossiles et géologie de l'Attique.' +1862.—'Le Dryopithèque.' <i>Mém. Soc. géol. de +France</i>: 'Paléontologie.' 1890. +</p> +<p> +<span class="smcap">O. Marsh</span>: 'Introduction and Succession of Vertebrate +Life in America.' Address, Amer. Assoc. Adv. Sci., +Nashville, 1887. +</p> +<p> +<span class="smcap">H. F. Osborn</span>: 'The Rise of the Mammalia in North +America.' Address, Amer. Assoc. Adv. Sci., Madison, +1893. +</p> +<p> +<span class="smcap">L. Ruetimeyer</span>: 'Ueber die Herkunft unserer Thierwelt,' +Basel, 1867. +</p> +<p> +<span class="smcap">C. S. Forsyth Major</span>: 'Fossil Monkeys from Madagascar.' +<i>Geological Magazine</i>, 1896. +</p> +<p> +<span class="smcap">M. Schlosser</span>: 'Ueber die Beziehungen der ausgestorbenen +Saeugethierfaunen und ihr Verhaeltniss zur Saeugethierfauna +der Gegenwart.' Biolog. Centralblatt, 1888.</p> +</blockquote> + +<p><a name="Footnote_16_16" id="Footnote_16_16"></a><a href="#FNanchor_16_16"><span class="label">[161</span></a> +See notes, p. <a name="FNanchor_47" id="FNanchor_47"></a><a href="#Footnote_47">102</a>, <a name="FNanchor_48" id="FNanchor_48"></a><a href="#Footnote_48">106</a>. </p> + +<p><a name="Footnote_17_17" id="Footnote_17_17"></a><a href="#FNanchor_17_17"><span class="label">[171</span></a> +See note, p. <a name="FNanchor_49" id="FNanchor_49"></a><a href="#Footnote_49">97</a>.</p> + +<p><a name="Footnote_18_18" id="Footnote_18_18"></a><a href="#FNanchor_18_18"><span class="label">[18]</span></a> Wilhelm Bischoff of Munich: works on the history +of the development of the rabbit, dog, guinea-pig, roe-deer. +1840-1854.</p> + +<p><a name="Footnote_19_19" id="Footnote_19_19"></a><a href="#FNanchor_19_19"><span class="label">[191</span></a> +See note, p. <a name="FNanchor_50" id="FNanchor_50"></a><a href="#Footnote_50">96</a>. </p> + +<p><a name="Footnote_20_20" id="Footnote_20_20"></a><a href="#FNanchor_20_20"><span class="label">[20]</span></a> 'Ueber die Entwicklung der einfachen Ascidien,' Mém. +Acad. St. Petersbourg, vii. ser., tome x. (1866). Other +papers in 'Archiv f. Mikroskop. Anatomie,' vii. (1871); xiii. +(1877).</p> + +<p><a name="Footnote_21_21" id="Footnote_21_21"></a><a href="#FNanchor_21_21"><span class="label">[21]</span></a> +See notes, p. <a name="FNanchor_51" id="FNanchor_51"></a><a href="#Footnote_51">102</a>, <a name="FNanchor_52" id="FNanchor_52"></a><a href="#Footnote_52">106</a>.</p> + +<p><a name="Footnote_22_22" id="Footnote_22_22"></a><a href="#FNanchor_22_22"><span class="label">[22]</span></a> Similar conditions seem to have prevailed among the +Proreptilia; but in those of their descendants which have +specialized into Reptiles and Birds the basi-occipital element +becomes more and more predominant in that formation +which ultimately leads to the apparently single condyle. +Hence it is misleading to divide the Tetrapoda into the two +main groups of Amphi-and Mono-condylia, and therefrom +to conclude that the two-condyled Mammalia are more +closely related to the likewise amphicondylous Amphibia +than to the so-called monocondylous Reptiles.</p> + +<p><a name="Footnote_23_23" id="Footnote_23_23"></a><a href="#FNanchor_23_23"><span class="label">[23]</span></a> 'Ergebnisse naturwissenschaftlicher Forschungen auf +Ceylon,' vols. 4 and 5. (With an atlas of 84 plates; 1893.)</p> + +<p><a name="Footnote_24_24" id="Footnote_24_24"></a><a href="#FNanchor_24_24"><span class="label">[24]</span></a> 'Principles of Biology': 'The Factors of Organic Evolution'; +'The Inadequacy of Natural Selection.'</p> + +<p><a name="Footnote_25_25" id="Footnote_25_25"></a><a href="#FNanchor_25_25"><span class="label">[25]</span></a> Abridged from Haeckel's 'Systematische Phylogenie +der Vertebraten,' § 14.</p> + +<p><a name="Footnote_26_26" id="Footnote_26_26"></a><a href="#FNanchor_26_26"><span class="label">[26]</span></a> That this great work is now comparatively rare, although +still in the second-hand market, may perhaps be urged in +excuse of the fact of so many attempts made by many authors, +both professional and amateur, to find fault with or to +explain the principles of adaptation, variation, heredity, +cænogenesis, phylogeny, etc., in complete ignorance that +all these and many more fundamental questions were fully +discussed more than thirty years ago in the 'Generelle Morphologie.'</p> + +<p><a name="Footnote_27_27" id="Footnote_27_27"></a><a href="#FNanchor_27_27"><span class="label">[27]</span></a> James Croll: 'On Geological Time, and the Probable +Date of the Glacial and Upper Miocene Period,' <i>Philos. +Magazine</i>, xxxv., 1868, pp. 363-384; xxxvi., pp. 141-154; +362-386.</p> + +<p><a name="Footnote_28_28" id="Footnote_28_28"></a><a href="#FNanchor_28_28"><span class="label">[28]</span></a> William Thomson: 'On the Secular Cooling of the +Earth,' <i>Transact. R. S. Edinb.</i>, xxiii., 1864, pp. 157-169.</p> + +<p><a name="Footnote_29_29" id="Footnote_29_29"></a><a href="#FNanchor_29_29"><span class="label">[29]</span></a> 'Geological Time as indicated by the Sedimentary +Rocks of North America.' <i>Proc. Amer. Assoc. Adv. Sci.</i>, +xlii., 1893, pp. 129-169.</p> + +<p><a name="Footnote_30_30" id="Footnote_30_30"></a><a href="#FNanchor_30_30"><span class="label">[30]</span></a> Henry Shaler Williams, 'Geological Biology.' New +York, 1895.</p> +</div> +</div> + +<p class= "transnote"> +Transcriber's Notes<br /> + + Variations in spelling, punctuation and hyphenation have been retained + except in obvious cases of typographical errors. + Inconsistent hyphenation and spelling are as in the original. + The layout of the chart Ancestral Tree of The Mammalia has been changed + from the original to enhance clarity, the essential relationships have + been preserved. + The second reference to footnote 3, in the same paragraph as the first, + has been left blind as it is redundant. +</p> + +<div>*** END OF THE PROJECT GUTENBERG EBOOK 44541 ***</div> +</body> +</html> diff --git a/44541-h/images/cover.jpg b/44541-h/images/cover.jpg Binary files differnew file mode 100644 index 0000000..dd90753 --- /dev/null +++ b/44541-h/images/cover.jpg diff --git a/44541-h/images/i_0231.jpg b/44541-h/images/i_0231.jpg Binary files differnew file mode 100644 index 0000000..52420cd --- /dev/null +++ b/44541-h/images/i_0231.jpg diff --git a/44541-h/images/i_0331.jpg b/44541-h/images/i_0331.jpg Binary files differnew file mode 100644 index 0000000..263fc4b --- /dev/null +++ b/44541-h/images/i_0331.jpg diff --git a/LICENSE.txt b/LICENSE.txt new file mode 100644 index 0000000..6312041 --- /dev/null +++ b/LICENSE.txt @@ -0,0 +1,11 @@ +This eBook, including all associated images, markup, improvements, +metadata, and any other content or labor, has been confirmed to be +in the PUBLIC DOMAIN IN THE UNITED STATES. + +Procedures for determining public domain status are described in +the "Copyright How-To" at https://www.gutenberg.org. + +No investigation has been made concerning possible copyrights in +jurisdictions other than the United States. Anyone seeking to utilize +this eBook outside of the United States should confirm copyright +status under the laws that apply to them. diff --git a/README.md b/README.md new file mode 100644 index 0000000..512b093 --- /dev/null +++ b/README.md @@ -0,0 +1,2 @@ +Project Gutenberg (https://www.gutenberg.org) public repository for +eBook #44541 (https://www.gutenberg.org/ebooks/44541) diff --git a/old/44541-8.txt b/old/44541-8.txt new file mode 100644 index 0000000..5aaf0b0 --- /dev/null +++ b/old/44541-8.txt @@ -0,0 +1,3418 @@ +The Project Gutenberg EBook of The Last Link, by Ernst Haeckel + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: The Last Link + Our Present Knowledge of the Descent of Man + +Author: Ernst Haeckel + +Commentator: Hans Gadow + +Release Date: December 29, 2013 [EBook #44541] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK THE LAST LINK *** + + + + +Produced by Chris Curnow, Les Galloway and the Online +Distributed Proofreading Team at http://www.pgdp.net (This +file was produced from images generously made available +by The Internet Archive) + + + + + + + THE LAST LINK + + OUR PRESENT KNOWLEDGE OF THE + DESCENT OF MAN + + BY + + ERNST HAECKEL + (JENA) + + WITH NOTES AND BIOGRAPHICAL SKETCHES + + BY + + HANS GADOW, F.R.S. + (CAMBRIDGE) + + + LONDON + ADAM AND CHARLES BLACK + 1898 + + + +CONTENTS + + + PAGE + THE LAST LINK + + INTRODUCTORY 1 + + COMPARATIVE ANATOMY 8 + + PALÆONTOLOGY 20 + + OTHER EVIDENCE 42 + + STAGES RECAPITULATED 47 + + BIOGRAPHICAL SKETCHES: + + LAMARCK, SAINT-HILAIRE, CUVIER, BAER, + MUELLER, VIRCHOW, COPE, KOELLIKER, GEGENBAUR, + HAECKEL 80 + + THEORY OF CELLS 115 + + FACTORS OF EVOLUTION 117 + + GEOLOGICAL TIME AND EVOLUTION 135 + + + + NOTE + + +The address I delivered on August 26 at the Fourth International +Congress of Zoology at Cambridge, 'On our Present Knowledge of the +Descent of Man,' has, I find, from the high significance of the theme +and the general importance of the questions connected with it, excited +much interest, and has led to requests for its publication. Hence this +volume, edited by my friend Dr. H. Gadow, my pupil in earlier days, +who has not only revised the text, but has also enriched it by many +valuable additions and notes. + + ERNST HAECKEL. + +_Jena, December, 1898._ + + + + + THE LAST LINK + + +At the end of the nineteenth century, the age of 'natural science,' the +department of knowledge that has made most progress is zoology. From +zoology has arisen the study of transformism, which now dominates the +whole of biology. Lamarck[1] laid its foundation in 1809, and forty +years ago Charles Darwin obtained for it a recognition which is now +universal. It is not my task to repeat the well-known principles of +Darwinism. I am not concerned to explain the scientific value of the +whole theory of descent. The whole of our biological study is pervaded +by it. No general problem in zoology and botany, in anatomy and +physiology, can be discussed without the question arising, How has this +problem originated? What are the real causes of its development? + + [1] See note, p. 80. + +This question was almost unknown seventy years ago, when Charles +Darwin, the great reformer of biology, began his academical career at +Cambridge as a student of theology. In the same year, 1828, Carl Ernst +von Baer[2] published in Germany his classical work on the embryology +of animals, the first successful attempt to elucidate by 'observation +and reflection' the mysterious origin of the animal body from the +egg, and to explain in every respect the 'history of the growing +individuality.' Darwin at that time had no knowledge of this great +advance, and he could not divine that forty years later embryology +would be one of the strongest supports of his own life's work--of that +very theory of transformism which, founded by Lamarck in the year of +Darwin's birth, was accepted with enthusiasm by Charles's grandfather +Erasmus. There is no doubt that of all the celebrated naturalists of +the nineteenth century Darwin achieved the greatest success, and we +should be justified in designating the last forty years as the Age of +Darwin. + + [2] See note, p. 89. + +In searching for the causes of this unexampled success, we must clearly +separate three sets of considerations: first, the comprehensive reform +of Lamarck's transformism, and its firm establishment by the many +arguments drawn from modern biology; secondly, the construction of the +new theory of selection, as established by Darwin, and independently +by Alfred Wallace (a theory called Darwinism in the proper sense); +thirdly, the deduction of anthropogeny, that most important conclusion +of the theory of descent, the value of which far surpasses all the +other truths in evolution. + +It is the third point of Darwin's theory that I shall discuss here; and +I shall discuss it chiefly with the intention of examining critically +the evidence and the different conclusions which at present represent +our scientific knowledge of the descent of man and of the different +stages of his animal pedigree. + +It is now generally admitted that this problem is the most important +of all biological questions. Huxley was right when in 1863 he called +it the question of questions for mankind. The problem which underlies +all others, and is more deeply interesting than any other, is as +to the place which man occupies in nature and his relations to the +universe of things. 'Whence our race has come; what are the limits of +our power over nature, and of nature's power over us; to what goal are +we tending--these are the problems which present themselves anew and +with undiminished interest to every man born into the world.' This +impressive view was explained by Huxley thirty-five years ago in his +three celebrated essays on 'Evidence as to Man's Place in Nature.' The +first is entitled 'On the Natural History of the Man-like Apes'; the +second, 'On the Relations of Man to the Lower Animals'; the third, 'On +some Fossil Remains of Man.' Darwin himself felt the burden of these +problems as much as Huxley; but in his chief work, 'On the Origin of +Species,' in 1859, he had purposely only just touched them, suggesting +that the theory of descent would shed light upon the origin of man and +his history. Twelve years later, in his celebrated work on 'The Descent +of Man, and Selection in Relation to Sex,' Darwin discussed fully and +ingeniously all the different sides of this 'question of questions' +from the morphological, historical, physiological, and psychological +points of view. As early as 1866 I myself had applied in the _Generelle +Morphologie der Organismen_ the theory of transformism to anthropology, +and had shown that the fundamental law of biogeny claims the same +value for man as for all the other animals. The intimate causal +connection between ontogeny and phylogeny, between the development of +the individual and the history of its ancestors, enables us to gain +a safe and certain knowledge of our ancestral series. I had at that +time distinguished in this series ten chief degrees of vertebrate +organization. I attributed the highest importance to the logical +connection of anthropogeny with transformism. If the latter be true, +the truth of the former is absolute. 'Our theory that man is descended +from lower vertebrates, and immediately from apes or primates, is a +case of special _deduction_ which follows with absolute certainty from +the general _induction_ of the theory of descent.' The full proof and +detailed explanation of this view was afterwards given in my 'History +of Natural Creation,' and especially in my 'Anthropogeny.'[3] Lastly, +it has received an ample scientific and critical foundation in the +third part of my 'Systematic Phylogeny.'[3] + + [3] See notes, pp. 102, 106 + +During the forty years which have elapsed since Darwin's first +publication of his theories an enormous literature, discussing the +_general problems_ of transformism as well as its special application +to man, has been published. In spite of the wide divergence of the +different views, all agree in one main point: the natural development +of man cannot be separated from general transformism. There are only +two possibilities. Either all the various species of animals and +plants have been created independently by supernatural forces (and +in this case the creation of man also is a miracle); or the species +have been produced in a natural way by transmutation, by adaptation +and progressive heredity (and in this case man also is descended from +other vertebrates, and immediately from a series of primates). We are +absolutely convinced that only the latter theory is fully scientific. +To prove its truth, we have to examine critically the strength of the +different arguments claimed for it. + + + + + I. + + +First, we have to consider the relative place which comparative +anatomy concedes to man in the 'natural system' of animals, for the +true value of our 'natural classification' is based upon its meaning +as a pedigree. All the minor and major groups of the system--the +classes, legions, orders, families, genera, and species--are only +different branches of the same pedigree. For man himself, his place +in the pedigree has been fixed since Lamarck,[4] in 1801, defined the +group of vertebrates. The most perfect[5] of these are the Mammalia; +and at the head of this class stands the order of Primates, in which +Linnæus, in 1735, united four 'genera'--Homo, Simia, Lemur, and +Vespertilio. If we exclude the last-named, the Chiroptera of modern +zoology, there remain three natural groups of Primates--the Lemures, +the Simiæ, and the Anthropi or Hominidæ. This is the classification of +the majority of zoologists; but if we compare man with the two chief +groups of monkeys--the Eastern monkeys (or Catarrhinæ) and the Western +or American monkeys (Platyrrhinæ)--there can be no doubt that the +former group is much more closely related to man than is the latter. +In the natural order of the Catarrhinæ we find united a long series +of lower and higher forms. The lowest, the Cynopitheci, appear still +closely related to the Platyrrhinæ and to the Lemures; while, on the +other hand, the tailless apes (Anthropomorphæ) approach man through +their higher organization. Hence one of our best authorities on the +Primates, Robert Hartmann,[6] proposed to subdivide the whole order of +the Simiæ into three groups: (1) Primarii, man together with the other +Anthropomorphæ, or tailless apes; (2) Simiæ, all the other monkeys; (3) +Prosimiæ, or Lemurs. This arrangement has received strong support from +the interesting discovery by Selenka that the peculiar placentation +of the human embryo is the same as in the great apes, and different +from that of all the other monkeys. Our choice between these different +classifications of Primates is best determined by the important thesis +of Huxley, in which, in 1863, he carried out a most careful and +critical comparison of all the anatomical gradations within this order. +In my opinion, this ingenious thesis--which I have called the Huxleyan +Law, or the 'Pithecometra-thesis of Huxley'--is of the utmost value. +It runs as follows: 'Thus, whatever system of organs be studied, the +comparison of their modifications in the ape-series leads to one and +the same result--that the structural differences which separate man +from the gorilla and the chimpanzee are not so great as those which +separate the gorilla from the lower apes.' If we accept the Huxleyan +law without prejudice, and apply it to the natural classification of +the Primates, we must concede that man's place is within the order +of the Simiæ. On examining this relation with care, and judging +with logical persistence, we may even go a step further. Instead of +the wider conception of 'Simiæ,' we must use the restricted term of +Catarrhinæ, and our Pithecometra-thesis has then to be formulated +as follows: _The comparative anatomy of all organs of the group of +Catarrhine Simiæ leads to the result that the morphological differences +between man and the great apes are not so great as are those between +the man-like apes and the lowest Catarrhinæ_. In fact, it is very +difficult to show why man should not be classed with the large apes in +the same zoological family. We all know a man from an ape; but it is +quite another thing to find differences which are absolute and not of +degree only. Speaking generally, we may say that man alone combines the +four following features: (1) Erect walk; (2) extremities differentiated +accordingly; (3) articulate speech; (4) higher reasoning power. Speech +and reason are obviously relative distinctions only--the direct result +of more brains and more brain-power, the so-called mental faculties. +The erect walk is not an absolutely distinguishing characteristic: the +large apes likewise walk on their feet only, supporting their bodies +by touching the ground with the backs of their hands--in fact, with +their knuckles--and this is a mode of progression very different from +that of the tailed monkeys, which walk upon the palms of their hands. +There are, however, two obvious differences in the development of the +muscles. In man alone the gastrocnemius and the soleus muscle are thick +enough to form the calf of the leg, and the glutæus maximus is enlarged +into the buttocks. A fourth glutæal muscle occurs occasionally in +man, while it is constantly present in apes as the so-called musculus +scansorius. Concerning the muscles of the whole body, we cannot do +better than quote Testut's summary: 'The mass of recorded observations +upon the muscular anomalies in man is so great, and the agreement of +many of these with the condition normal in apes is so marked, that the +gap which usually separates the muscular system of man from that of the +apes appears to be completely bridged over.' + + [4] See note, p. 80. + + [5] _Perfect_, in the sense of highest stage of evolution, may seem a + _petitio principii_. Leaving aside the consideration that no living + creature is absolutely perfect, in the sense that its organization + cannot become more efficient or proficient, we have here to deal with + relative perfection of the whole organization. A fish or a snake is in + its way more specialized than a mammal; but specialization does not + necessarily mean height of development: it generally means life in a + comparatively narrow groove. The acts of giving birth and nourishing + the young with the mother's milk is a much higher stage than the act + of laying eggs and letting them run their chance. The development of + a hairy coat goes along with heightened temperature of the blood, + subsequent greater independence of the surrounding temperature, and + increased steady activity of the brain and other nerve-centres. The + brain of the Mammalia, in its minute structure, is much more complex. + This rule applies to some of the principal sense organs, chiefly the + nose and the ear. The skeleton, not so much as a whole as in the + various bones and joints, is more neatly finished, and built up more + in conformity with 'scientific principles,' than is the case even with + birds, in spite of their marvellous specialization. The same is the + case with the vascular system, notably the heart and the veins, and + with the excretory organs. In all of these many imperfections, still + to be found in the other classes, have been corrected in Mammalia. The + Primates take an easy first by their hands, and among them the apes and + man himself by their brains. + + [6] 'Die menschenähnlichen Affen und ihre Organisation im Vergleich zur + menschlichen.' 1883. + +There are, for example, the muscles of the ear. In most people the +majority, or even all of them, are no longer movable at will, while in +the apes they are still in use. The important point, however, is that +these muscles are still present in man, although often in a reduced +condition. They are the following: (1) Musculus auricularis anterior +or attrahens auris, which is frequently much reduced and no longer +reaches the ear at all, being then absolutely useless; (2) Musculus +auricularis superior or attollens auris, more constant than the former; +(3) Musculus auricularis posterior or retrahens auris, likewise often +functional. Occasionally smaller slips differentiated from these +three muscles are present, and as so-called intrinsic muscles are +restricted to the ear itself; their function is, or was, that of +curling up or opening the external ear. + +[Illustration: OUTLINES OF THE LEFT EAR OF-- + +1. _Lemur macaco_; 2. _Macacus rhesus_, the Rhesus monkey; 3. +Cercopithecus, a macaque; 4. human embryo of six months; 5. man, with +Darwin's point well retained: the dotted outline is that of the ear of +a baboon; 6. orang-utan (after G. Schwalbe):[7] ^x the original tip of +the ear; 7. human ear with the principal muscles. + + [7] G. Schwalbe, 'In wiefern ist die menschliche Ohrmuschel ein + rudimentäres Organ?'--In what Respects is the Human Outer Ear a + Rudimentary Organ? (_Archiv f. Anatomie und Physiologie_, 1889).] + +In connection with the ear, I may touch upon another interesting +and most suggestive little feature which is present in many +individuals--namely, 'Darwin's point.' This is the last remnant of the +original tip of the ear, before the outer, upper, and hinder rim became +doubled up or folded in. It is a feature quite useless, and absolutely +impossible of interpretation, excepting as the vestige of such previous +ancestral conditions as are normal in the monkeys. + +In some cases the reduction of muscles has proceeded further in apes +than in man--for example, the muscles of the little toe. Another +instance is afforded by the coccyx or vestige of the tail; this is +still furnished with muscles which are now in man, as well as in +the apes, quite useless, and vary considerably with every sign of +degeneration, most so in the orang-utan. + +Darwin has mentioned the frequent action of the 'snarling muscle,' by +which, in sneering, our upper canine teeth are exposed, like those of a +dog prepared to fight. + +Monkeys and apes possess vocal sacs, especially large in the +orang-utan; survivals of them, although no longer used, persist in man +in the shape of a pair of small diverticula, the pouches of Morgagni, +between the true and the false vocal cords. + +'In the native Australians, the dental formula appears least removed +from the hypothetical original type, for in it are still found complete +rows of splendid teeth, with powerfully-developed canines and molars, +the latter being either uniform, or even increasing in size, as we +proceed backwards, in such a way that the wisdom tooth is the largest +of the series. This is decidedly a pithecoid characteristic which is +always found in apes. The upper incisors of the Malay, apart from their +prognathous disposition, have occasionally a distinctly pithecoid +form, their anterior surface being convex, and their lingual surface +slightly concave. The ancestors of Europeans seem to have had the same +form of teeth, for the oldest existing fragments of skulls from the +Mammoth age (_e.g._, the jaws from La Naulette, in Belgium) reveal +tooth-forms which must be classed with those of the lowest races of +to-day.'[8] + + [8] Wiedersheim, 'Der Bau des Menschen als Zeugniss für seine + Vergangenheit.' Freiburg, 1888. Translated: 'The Structure of Man an + Index to his Past History.' London, 1895. + +Now we are able to apply this fundamental Pithecometra-thesis directly +to the classification of the Primates and to the phylogeny of man, +which is intimately connected with it, because in this order, as in +all the other groups of animals, the natural system is the clear +expression of true phylogenetic affinity. Four results follow from our +thesis: (1) The Primates, as the highest legion or order of mammals, +form one natural, monophyletic group. All the Lemures, Simiæ, and +Homines descend from one common ancestral form, from a hypothetical +'Archiprimas.' (2) The Lemures are the older and lower of the natural +groups of the Primates; they stand between the oldest Placentalia +(Prochoriata) and the true Simiæ. (3) All the Catarrhinæ, or Eastern +Simiæ, form one natural monophyletic group. Their hypothetical +common ancestor, the Archipithecus, may have descended directly or +indirectly from a branch of the Lemures. (4) Man is descended directly +from one series of extinct Catarrhine ancestors. The more recent +ancestors of this series were tailless anthropoids (similar to the +Anthropopithecus), with five sacral vertebræ. The more remote ancestors +were tailed Cercopitheci, with three or four sacral vertebræ. + +These four theses possess, in my opinion, absolute certainty. +They are independent of all future anatomical, embryological, and +palæontological discoveries which may possibly throw more light upon +the details of our phyletic anthropogenesis. + + + + + II. + + +The next question is, how the facts of palæontology agree with these +most important results of comparative anatomy and ontogeny. The fossils +are the true historical 'medals of creation,' the palpable evidence of +the historical succession of all those innumerable organic forms which +have peopled the globe for many millions of years. Here the question +arises, If the known fossil specimens of Mammalia, and particularly +of Primates, give proof of these Pithecometra-theses, do they confirm +directly the descent of man from ape-like creatures? The answer to this +question is, in my opinion, affirmative. + +It is true that the gaps in the palæontological evidence, here as +elsewhere, are many and keenly felt. In the order of the Primates +they are greater than in many other orders, chiefly because of the +arboreal life of our ancestors. The explanation is very simple. It is +really due to a long chain of favourable coincidences if the skeleton +of a vertebrate, covered as it was with flesh and skin, and containing +still more perishable viscera, is petrified at all. The body may be +devoured by other creatures, and its bones scattered about; or it rots +away and crumbles to pieces. Many animals hide in thick undergrowth +when death approaches them; and, leading an almost entirely arboreal +life, the Primates are especially likely to disappear without being +fossilized. It is only when the body is quickly covered with sand, or +is embedded in suitable lime or silica containing mud, that the process +of petrifaction can come to pass. Even then it is only by great good +luck that we come across such a fossil. Very few countries have been +searched systematically, and the areas that have been searched amount +to little in comparison with the whole surface of the land, even if we +leave out of account the fact that more than two-thirds of the globe +are covered by water. + +These deplorable deficiencies of empirical palæontology are balanced +on the other side by a growing number of positive facts, which possess +an inestimable value in human phylogeny. The most interesting and most +important of these is the celebrated fossil _Pithecanthropus erectus_, +discovered in Java in 1894 by Dr. Eugène Dubois.[9] Three years ago +this now famous ape-like man provoked an animated discussion at the +third International Zoological Congress at Leyden. I may therefore +be allowed to say a few words as to its scientific significance. +Unfortunately, the fossil remains of this creature are very scanty: the +skull-cap, a femur, and two teeth. It is obviously impossible to form +from these scanty remains a complete and satisfactory reconstruction of +this remarkable Pliocene Primate. + +[9] _Pithecanthropus erectus._ 'Eine menschenähnliche Uebergangsform +aus Java' ('A Human-like Transitional Form'). Batavia, 1894. + +The more important points are the following: The remains in question +rested upon a conglomerate which lies upon a bed of marine marl and +sand of Pliocene age. Together with the bones of Pithecanthropus were +found those of Stegodon, Leptobos, Rhinoceros, Sus, Felis, Hyæna, +Hippopotamus, Tapir, Elephas, and a gigantic Pangolin. It is remarkable +that the first two of these genera are now extinct, and that neither +hippopotamus nor hyæna exists any longer in the Oriental region. If we +may judge from these fossil remains, the bones of Pithecanthropus are +not younger than the oldest Pleistocene, and probably belong to the +upper Pliocene. The teeth are like those of man. The femur, also, is +very human, but shows some resemblances to that of the gibbons. Its +size, however, indicates an animal which stood when erect not less +than 5 feet 6 inches high. The skull-cap also is very human, but with +very prominent eyebrow ridges, like those of the famous Neanderthal +cranium. It is certainly not that of an idiot. It had an estimated +cranial capacity of about 1,000 cubic centimetres--that is to say, much +more than that of the largest ape, which possesses not more than 600 +c.c. The crania of female Australians and Veddahs measure not more than +1,100, some even less than 1,000 c.c.; but, as these Veddah women stand +only about 4 feet 9 inches high, the computed cranial capacity of the +much taller Pithecanthropus is comparatively very low indeed.[10] + + [10] On the day after the delivery of this address Dr. Dubois exhibited + the cranium of Pithecanthropus, from which he had removed the stony + matrix which filled the inside, in order to examine the impression left + by the cerebral convolutions. He was able to show that they also are + very human, and more highly developed than those of the recent apes. [ + Illustration: The upper figure represents the outlines + of the skull of Pithecanthropus, as restored by Manouvier.[11] The + lower figure shows the comparative size and shape of Pithecanthropus, + the Neanderthal skull, a specimen of the Cro-Magnon race of neolithic + France, and a Young Chimpanzee before the full development of the + supraorbital crests.] + + [11] L. Manouvier: 'Deuxième étude sur le Pithecanthropus erectus comme + précurseur présumé de l'homme.' (_Bulletins de la Soc. d'Anthropologie + de Paris_, 1895.) + +The final result of the long discussion at Leyden was that, of twelve +experts present, three held that the fossil remains belonged to a low +race of man; three declared them to be those of a man-like ape of great +size; the rest maintained that they belonged to an intermediate +form, which directly connected primitive man with the anthropoid +apes. This last view is the right one, and accords with the laws of +logical inference. _Pithecanthropus erectus_ of Dubois is truly a +Pliocene remainder of that famous group of highest Catarrhines which +were the immediate pithecoid ancestors of man. He is, indeed, the +long-searched-for 'missing link,' for which, in 1866, I myself had +proposed the hypothetical genus Pithecanthropus, species Alalus. + +It must, however, be admitted that this opinion is still strongly +combated by some distinguished authorities. At the Leyden Congress it +was attacked by the illustrious pathologist Rudolf Virchow.[12] He, +however, is one of the minority of leading men of science who set +themselves to refute the theory of Evolution in every possible way. For +thirty years he has defended the thesis: 'It is quite certain that man +is not a descendant of apes.' He declares any intermediate form to be +unimaginable save in a dream. + + [12] See Notes, p. 93. + +Virchow went to the Leyden Congress with the set purpose of disproving +that the bones found by Dubois belonged to a creature which linked +together apes and man. First, he maintained that the skull was that +of an ape, while the thigh belonged to man. This insinuation was at +once refuted by the expert palæontologists, who declared that without +the slightest doubt the bones belonged to one and the same individual. +Next, Virchow explained that certain exostoses or growths observable on +the thigh proved its human nature, since only under careful treatment +the patient could have healed the original injury. Thereupon Professor +Marsh, the celebrated palæontologist, exhibited a number of thigh-bones +of wild monkeys which showed similar exostoses and had healed without +hospital treatment. As a last argument the Berlin pathologist declared +that the deep constriction behind the upper margin of the orbits +proved that the skull was that of an ape, as such never occurred in +man. It so happened that a few weeks later Professor Nehring of Berlin +demonstrated exactly the same formation on a human prehistoric skull +received by him from Santos, in Brazil. + +Virchow was, in fact, just as unlucky in Leyden in his fight with our +pliocene ancestor as he had been unfortunate in his opinion on the +famous skulls of Neanderthal, Spy, La Naulette, etc., every one of which +he explained as a pathological abnormality. It would be a very curious +coincidence indeed if all these and other fossil human remains were +those of idiots or otherwise abnormal individuals, provided they are +old and low enough in their organization to be of phylogenetic value to +the unbiassed zoologist. + +As the sworn adversary of Evolution, transformism, and Darwinism in +particular, but a believer in the constancy of species, the great and +renowned pathologist has been driven to the incredible contention that +all variations of organic forms are pathological. + +Four years ago, as honorary president of the Anthropological Congress +at Vienna, he attacked Darwinism in the severest manner, and declared +that 'man may be as well descended from the elephant or from the sheep +as from the ape.' Such attacks on the theory of transformism indicate a +failure to understand the principles of the theory of Evolution and to +appreciate the significance of palæontology, comparative anatomy, and +ontogeny. + +The thousands of other objections which have been made during the last +forty years (chiefly by outsiders) may be passed over in silence. They +do not require serious refutation. In spite of, or perhaps because of, +these attacks, the theory of Evolution stands established more firmly +than ever. + +It is easy for the outsider to exult over the difficulties which our +problem implies--difficulties which we who have given our lives to the +study understand likewise, and try our best not only to bridge over, +but also to point out. Anyhow, we do not conceal them; while those who +reject the explanation offered by Evolution make the most of the gaps, +and pass silently over the far more numerous points favourable to our +theory. + +How fruitful during the last thirty years the astonishing progress in +our palæontological knowledge has been for our Pithecometra-thesis is +best shown by a short glance at the growth of our knowledge of fossil +Primates. Cuvier,[13] the founder of palæontology, continued up to the +time of his death, in 1832, to assert that fossil remains of monkeys +and lemurs did not exist. The only skull of a fossil lemuroid which +he described (namely, Adapis) he declared to be that of an ungulate. +Not until 1836 were the first fragments of extinct monkeys found in +India; it was two years later, near Athens, that the skeleton of +_Mesopithecus penthelicus_ was discovered. Other remains of lemurs were +found in 1862. But during the last twenty years the number of fossil +Primates has been augmented by the remarkable discoveries of Gaudry, +Filhol, Milne Edwards, Seeley, Schlosser, and others in Europe; of +Marsh, Cope, Osborn, Leidy, Ameghino, in South America; and Forsyth +Major in Madagascar.[14] These tertiary remains, chiefly of Eocene and +Miocene date, fill many gaps between existing genera of Primates, and +afford us quite a clear insight into the phyletic development of this +order during the millions of years of the Cænozoic age. + + [13] See notes, p. 87. + + [14] + F. AMEGHINO: 'Contribucion al conocimiento de los mamíferos + de la república Argentina.' In _Actas de la Academia nacional de + Sciencias en Cordoba_, 1889.--Another article in _Revista Argentina de + Historia natural_. Buenos Aires, 1891. + + A. GAUDRY: 'Animaux fossiles et géologie de l'Attique.' + 1862.--'Le Dryopithèque.' _Mém. Soc. géol. de France_: + 'Paléontologie.' 1890. + + O. MARSH: 'Introduction and Succession of Vertebrate Life in + America.' Address, Amer. Assoc. Adv. Sci., Nashville, 1887. + + H. F. OSBORN: 'The Rise of the Mammalia in North America.' + Address, Amer. Assoc. Adv. Sci., Madison, 1893. + + L. RUETIMEYER: 'Ueber die Herkunft unserer Thierwelt,' Basel, + 1867. + + C. S. FORSYTH MAJOR: 'Fossil Monkeys from Madagascar.' + _Geological Magazine_, 1896. + + M. SCHLOSSER: 'Ueber die Beziehungen der ausgestorbenen + Saeugethierfaunen und ihr Verhaeltniss zur Saeugethierfauna der + Gegenwart.' Biolog. Centralblatt, 1888. + +The most important difference between the two groups of existing +monkeys is indicated by their dentition. Adult man possesses, like +all the other Catarrhine Simiæ, thirty-two teeth, whilst the American +monkeys (the Platyrrhinæ) have thirty-six teeth--namely, one pair of +premolars more in the upper and lower jaws. Comparative odontology +leads us to the phylogenetic conclusion that this number has been +produced by reduction from a still older form with forty-four teeth. +This typical dental formula (three incisors, one canine, four +premolars, and three molars, in each half-jaw) is common to all those +most important older mammals which in the beginning of the Eocene +period constituted the four large groups of Lemuravida, Condylarthra, +Esthonychida, and Ictopsida. These are the four ancestral groups +of the four main orders of Placentalia--namely, of the Primates, +Ungulata, Rodentia, and Carnassia. They seem to be so closely related +by their primitive organization that they may be united in one common +super-order, Prochoriata. + +With a considerable degree of probability, we are led to formulate +the further hypothesis that all the orders of Placentalia--from the +lowest Prochoriata upwards to man--have descended from some unknown +common ancestor living in the Cretaceous period, and that this oldest +placental form originated from some Jurassic group of marsupials. + +Among these numerous fossil Lemures which have been discovered within +the last twenty years, there exist, indeed, all the connecting forms +of the older series of Primates, all the 'missing links' sought for by +comparative odontology. + +The oldest Lemures of the tertiary age are the Eocene Pachylemures, +or Hyopsodina. They possess the complete dentition of the +Prochoriata--namely, forty-four teeth (3.1.4.3/3.1.4.3). Then follow +the Eocene Palæolemures, or Adapida, with forty teeth, they having lost +one pair of incisors in each jaw. To these are attached the younger +Autolemures, or Stenopida, with thirty-six teeth, they thus possessing +already the same dentition as the Platyrrhinæ. The characteristic +dentition of the Catarrhinæ is derived from this formula by the loss of +another premolar. + +These relations are so clear and so closely connected with a +gradual transformation of the whole skull, and with the progressive +differentiation of the Primate-form, that we are justified in saying +that the pedigree of the Primates, from the oldest Eocene Lemures +upwards to man, is now so well known, its principal features so firmly +fixed within the Tertiary age, that there is no missing link whatever. + +Quite different, and much more incomplete, is the palæontological +evidence, if we go further back into the Secondary or Mesozoic age, +and look there for the older ancestors of the mammalian series. There +we meet everywhere with wide gaps, and the scarce fragments of fossil +Mesozoic mammals (excessively rare in the Cretaceous formation) are too +poor to permit definite conclusions as to their systematic position. +Indeed, comparative anatomy and ontogeny lead us to the hypothesis +that the oldest Cretaceous Mammalia--the Prochoriata--are descended +from Jurassic marsupials, and these again from Monotremes. We may +also suppose with high probability that among the unknown Cretaceous +Prochoriata there have been Lemuravida and forms intermediate between +these and the Jurassic Amphitheriidæ, and that these marsupials in +their turn are descendants of Pantotheria or similar monotreme-like +creatures of the Triassic age. Any certain evidence for these +hypotheses is at present still wanting. One important fact, however, +is established--namely, that these interesting and oldest Mammalia--the +Pantotheria of Marsh, the Triassic Dromatheriidæ, and the Jurassic +Triconodontidæ of Osborn--were small insectivorous mammals with a very +primitive organization. Probably they were Monotremes, and may be +derived directly from Permian Sauromammalia, an ill-defined mixture of +Mammalia and Reptilia. + +This generalized characteristic supports our view that _the whole +class of Mammalia is monophyletic_, and that all its members, from +the oldest Monotremes upwards to man, have descended from one common +ancestor living in the older Triassic, or perhaps in the Permian, +age. To acquire full conviction of this important conception, we have +only to think of the hair and the glands of our human skin, of our +diaphragm, the heart and the blood corpuscles without a nucleus, our +skull with its squamoso-mandibular articulation. All these singular +and striking modifications of the vertebrate organization are common +to mammals, and distinguish them clearly from the other Craniota. This +characteristic combination and correlation proves that they have been +developed only _once_ in the history of the vertebrate stem, and that +they have been transferred by heredity from one common ancestor to all +the members of the class of Mammalia. + +The next step, as we trace our human phylogeny to its origin, leads us +further back into the lower Vertebrata, into that obscure Palæozoic +age the immeasurable length of which (much greater than that of the +Mesozoic) may, according to one of the newest geological calculations, +have comprised about one thousand millions of years.[15] + + [15] See note, 'Geological Time and Evolution' p. 134. + +The first important fact we have to face here is the complete absence +of mammalian remains. Instead of these we find in the later Palæozoic +period, the Permian, air-breathing _reptiles_ as the earliest +representatives of Amniota. They belong to the most primitive order +of that class, the Tocosauria; and besides them there were the +Theromorpha, which approach the Mammalia in a remarkable manner. These +reptiles in turn were preceded, in the Carboniferous period, by true +Amphibia, most of them belonging to the armour-clad Stegocephali. +These interesting Progonamphibia were the oldest Tetrapoda, the first +vertebrates which had adapted themselves to the terrestrial mode of +life; in them the swimming fin of fishes and Dipneusta was transformed +into the pentadactyle extremities characteristic of quadrupeds. + +To appreciate the high importance of this metamorphosis, we need only +compare the skeleton of our own human limbs with that of the living +Amphibia. We find in the latter the same characteristic composition as +in man: the same shoulder and pelvic girdle; the same single bone, the +humerus or the femur, followed by the same pair of bones in the forearm +and leg; then the same skeletal elements composing the wrist and the +ankle regions; and, lastly, the same five fingers and toes. + +The arrangement of these bones, peculiar and often complicated, but +everywhere essentially the same in all the Tetrapoda, is a striking +evidence that man is a descendant from the oldest pentadactyle Amphibia +of the Carboniferous period. In man the pentadactyle type has been +better preserved by constant heredity than in many other Mammalia, +notably the Ungulata. + +The oldest Carboniferous Amphibia, the armour-clad Stegocephali, and +especially the remarkable Branchiosauri discovered by Credner, are +now regarded by all competent zoologists as the indubitable common +ancestral group of all Tetrapoda, comprising both Amphibia and Amniota. +But whence this most remote group of Tetrapoda? That difficult question +is answered by the marvellous progress of modern palæontology, and +the answer is in complete harmony with the older results arrived +at by comparative anatomy and ontogeny. Thirty-four years ago Carl +Gegenbaur,[16] the great living master of comparative anatomy, had +demonstrated in a series of works how the skeletal parts of the various +classes of Vertebrata, especially the skull and the limbs, still +represent a continuous scale of phyletic gradations. Apart from the +Cyclostomes, there are the fishes, and among them the Elasmobranchi +(sharks and rays), which have best preserved the original structure in +all its essential parts of organization. Closely connected with the +Elasmobranchi are the Crossopterygii, and with these the Dipneusta or +Dipnoi. Among the latter the highest importance attaches to the ancient +Australian Ceratodus. Its organization and development is now, at last, +becoming well known. This transitional group of Dipnoi, 'fishes with +lungs' but without pentadactyle limbs, is the morphological bridge +which joins the Ganoids and the oldest Amphibia. With this chain +of successive groups of Vertebrata, constructed anatomically, the +palæontological facts agree most satisfactorily. Selachians and Ganoids +existed in the Silurian times, Dipnoi in the Devonian, Amphibia in the +Carboniferous, Reptilia in the Permian, Mammalia in the Trias. These +are historical facts of first rank. They connote in the most convincing +manner that remarkable ascending scale in the series of vertebrates +for our knowledge of which we are indebted to the works of Cuvier and +Blainville, Meckel, Johannes Mueller and Gegenbaur, Owen and Huxley. +The historical succession of the classes and orders of the Vertebrata +in the course of untold millions of years is definitely fixed by the +concordance of those leading works, and this invaluable acquisition is +much more important for the foundation of our human pedigree than would +be a complete series of all possible skeletons of Primates. + + [16] See note, p. 97. + +Greater and more frequent difficulties arise if we penetrate further +into the most remote part of the human phylogeny, and attempt to derive +the vertebrate stem from an older stem of invertebrate ancestors. None +of those had a skeleton which could be petrified; and the same remark +applies to the lowest classes of Vertebrata--to the Cyclostomes and +the Acrania. Palæontology, therefore, can tell us nothing about them; +and we are limited to the other two great documents of phylogeny--the +results of comparative anatomy and ontogeny. The value of their +evidence is, however, so great that every competent zoologist can +perceive the most important features of the most remote portion of our +phylogeny. + +Here the first place belongs to the invaluable results which modern +comparative ontogeny has gained by the aid of the biogenetic law or +the theory of recapitulation. The foundation-stones of vertebrate +embryology had been laid by the works of Von Baer, Bischoff,[17] Remak, +and Koelliker;[18] but the clearest light was thrown upon it by the +famous discoveries of Kowalevsky[19] in 1866. He proved the identity +of the first developmental stages of Amphioxus and the Ascidians, and +thereby confirmed the divination of Goodsir, who had already announced +the close affinity of Vertebrates and Tunicates. The acknowledgment of +this affinity has proved of increasing importance, and has abolished +the erroneous hypothesis that the Vertebrata may have arisen from +Annelids or from other Articulata. Meanwhile, from 1860 to 1872, I +myself had been studying the development of the Spongiæ, Medusæ, +Siphonophora, and other Coelenterata. Their comparison led me to the +statements embodied in the 'Gastræatheorie,' the first abstract of +which was published in 1872 in my monograph of the Calcispongiæ. + + [17] Wilhelm Bischoff of Munich: works on the history of the + development of the rabbit, dog, guinea-pig, roe-deer. 1840-1854. + + [18] See note, p. 96. + + [19] 'Ueber die Entwicklung der einfachen Ascidien,' Mém. Acad. St. + Petersbourg, vii. ser., tome x. (1866). Other papers in 'Archiv f. + Mikroskop. Anatomie,' vii. (1871); xiii. (1877). + +These ideas were carried on and expanded during the subsequent ten +years by the help of many excellent embryologists--first of all by E. +Ray Lankester and Francis Balfour. The most fruitful result of these +widely extended researches was the conclusion that the first stages of +embryonic development are essentially the same in all the different +Metazoa, and that we may derive from these facts certain views on +the common descent of all from one ancestral form. The unicellular +egg[20] repeats the stage of our Protozoan ancestors; the Blastula +is equivalent to an ancestral coenobium of Magosphæra or Volvox; +the Gastrula is the hereditary repetition of the Gastræa, the common +ancestor of all the Metazoa. + + [20] See note, p. 115--Theory of cells. + +Man agrees in all these respects with the other vertebrates, and must +have descended with them from the same common root. + +Particularly obscure is that part of our phylogeny which extends from +the Gastræa to Amphioxus. The morphological importance of this last +small creature had been perceived by Johannes Mueller, who in 1842 +gave the first accurate description of it. It would not, of course, be +correct to proclaim the modern Amphioxus the common ancestor of all the +vertebrates; but he must be regarded as closely related to them, and +as the only survivor of the whole class of Acrania. If the Amphioxidæ +had through some unfortunate accident become extinct, we should not +have been able to gain anything like a positive glimpse at our most +remote vertebrate ancestor. On the one hand, Amphioxus is closely +connected with the early larva of the Cyclostomes, which are the +oldest Craniota, and the pre-Silurian ancestors of the fishes. On the +other hand, the ontogeny of Amphioxus is in harmony with that of the +Ascidians, and if this agreement is not merely coincidental, but due to +relationship, we are justified in reconstructing for both Ascidians +and Amphioxus one common ancestral group of chordate animals, the +hypothetical _Prochordonia_. The modern Copelata give us a remote idea +of their structure. The curious Balanoglossus, the only living form of +Enteropneusta, seems to connect these Prochordonia with the Nemertina +and other Vermalia, which we unite in one large class--Frontonia. + +No doubt these pre-Cambrian Vermalia, and the common root of all +Metazoa, the Gastræades, were connected during the Laurentian period +by a long chain of intermediate forms, and probably among these +were some older forms of Rotatoria and Turbellaria; but at present +it is not possible to fill this wide gap with hypotheses that are +satisfactory, and we have to admit that here indeed are many missing +links in the older history of the Invertebrata. Still, every zoologist +who is convinced of the truth of transformism, and is accustomed to +phylogenetic speculations, knows very well that their results are most +unequal, often incomplete. + + + + +III. + + +Let us now recapitulate the ancestral chain of man, as it is set forth +in the accompanying diagram (p. 55), which represents our present +knowledge of our descent. For simplicity's sake the many side-issues +or branches which lead to groups not in the main line of our descent +have been left out, or have been indicated merely. Many of the stages +are of course hypothetical, arrived at by the study of comparative +anatomy and ontogeny; but an example for each of them has been taken +from those living or fossil creatures which seem to be their nearest +representatives. + +1. The most remote ancestors of all living organisms were living beings +of the simplest imaginable kind, organisms without organs, like +the still existing _Monera_. Each consisted of a simple granule of +protoplasm, a structureless mass of albuminous matter or plasson, like +the recent Chromaceæ and Bacteriæ. The morphological value of these +beings is not yet that of a cell, but that of a cytode, or cell without +a nucleus. Cytoplasm and nucleus were still undifferentiated. + +I assume that the first Monera owe their existence to spontaneous +creation out of so-called anorganic combinations, consisting of carbon, +hydrogen, oxygen, and nitrogen. An explanation of this hypothesis I +have given in my 'Generelle Morphologie.' + +The Monera probably arose early in the Laurentian period. The oldest +are the Phytomonera, with vegetable metabolism. They possessed the +power (characteristic of plants) of forming albumin by synthesis from +carbon, water, and ammonia. From some of these plasma-forming Monera +arose the plasmophagous Zoomonera with animal metabolism, living +directly upon the produce of their plasmodomous or plasma-forming +sisters. This is the first instance of the great principle of division +of labour. + +2. The second stage is that of the _simple and single cell_, a bit +of protoplasm with a nucleus. Such unicellular organisms are still +very common. The _Amoebæ_ are their simplest representatives. The +morphological value of such beings is the same as that of the egg +of any animal. The naked egg cells of the sponges creep about in an +amoeboid fashion, scarcely distinguishable from Amoeba. The same +remark applies to the egg-cell of man himself in its early stages +before it is enclosed in a membrane. The first unicellular organisms +arose from Monera through differentiation of the inner nucleus from the +outer protoplasm. + +3. Repeated division of the unicellular organism produces the +_Synamoebium_, or community of Amoebæ, provided the divisional +products, or new generations of the original cell, do not scatter, +but remain together. The existence of such a _Coenobium_, a number +of equal and only loosely-connected cells, as a separate stage in the +ancestral history of animals, is made highly probable by the fact that +the eggs of all animals undergo after fertilization such a process of +repeated self-division, or 'cleavage,' until the single egg cell is +transformed into a heap of cells closely packed together, not unlike a +mulberry (_morula_)--hence _morula_ stage in ontogeny. + +4. The morula of most animals further changes into a _Blastula_, a +hollow ball filled with fluid, the wall being formed by a single layer +of cells, the blastoderm or germinal layer. This modification is +brought about by the action of the cells--they conveying nourishing +fluid into the interior of the whole cell colony and thereby +being themselves forced towards the surface. The Blastula of most +Invertebrata, and even that of Amphioxus, is possessed of fine ciliæ, +or hair-like processes, the vibrating motion of which causes the whole +organism to rotate and advance in the water. Living representatives of +such Blastæads, namely, globular gelatinous colonies of cells enclosing +a cavity, are Volvox and Magosphæra. + +5. The Blastula of most animals assumes a new larval form called +_Gastrula_, in which the essential characteristics are that a portion +of the blastoderm by invagination converts the Blastula into a cup +with double walls, enclosing a new cavity, the primitive gut. This +invagination or bulging-in obliterates the original inner cavity of +the Blastula. The outer layer of the Gastrula is the ectoderm, the +inner the endoderm; both pass into each other at the blastoporus, or +opening of the gut cavity. The Gastrula is a stage in the embryonic +development of the various great groups of animals, and some such +primitive form as ancestral to all Metazoa is thus indicated. This +hypothetical _Gastræa_ is still very essentially represented by the +lower Coelenterates--_e.g._, Olynthus, Hydra. + +6. The sixth stage--that of the _Platodes_, or flat-worms--is very +hypothetical. They are bilateral gastræads, with a flattened oblong +body, furnished with ciliæ, with a primitive nervous system, simple +sensory and reproductive organs, but still without appendages, body +cavity, vent, and blood-vessels. The nearest living representatives of +such creatures are the acoelous Turbellarians--_e.g._, Convoluta, a +free-swimming, ciliated creature. + +7. The next higher stage is represented by such low animals as the +_Gastrotricha_--_e.g._, Chætonotus among the Rotatoria, which differ +from the rhabdocoelous Turbellarians chiefly by the formation of +a vent and the beginnings of a coelom, or cavity, between gut and +body wall. The addition of a primitive vascular system and a pair of +nephridia, or excretory organs, is first met with in the _Nemertines_. + +8. These, together with the _Enteropneusta_ (Balanoglossus), are +comprised under the name of Frontonia, or Rhynchelminthes, and form the +highest group of the Vermalia. + +The Enteropneusta especially fix our attention, because they alone, +although essentially 'worms,' exhibit certain characteristics which +make it possible to bridge over the gulf which still separates the +Invertebrata from the vertebrate phylum. The anterior portion of the +gut is transformed into a breathing apparatus--hence Gegenbaur's +term of Enteropneusta, or Gut-breathers. Moreover, Balanoglossus and +Cephalodiscus possess another modification of the gut--namely, a +peculiar diverticulum, which, in the present state of our knowledge, +may be looked upon as the forerunner of the chorda dorsalis. + +9. Stage of _Prochordonia_, as indicated by the larval form, called +Chordula, which is common to the Tunicata and all the Vertebrata. +These two groups possess three most important features: (_a_) A chorda +dorsalis, a stiff rod lying in the long axis of the body, dorsally from +the gut and below the central nervous system. This latter, for the +first time in the animal kingdom, appears in the shape of a spinal +cord. (_b_) The use of the anterior portion of the gut for respiratory +purposes. (_c_) The larval development of the Tunicata is essentially +the same as that of the Vertebrata in its early stages. Only the +free-swimming Copelata or Appendicularia among the Tunicates retain +most of these features. The others, which become sessile--namely, the +Ascidiæ, or sea-squirts--degenerate and specialize away from the main +line. + +10. Stage of the _Acrania_, represented by Amphioxus. The early +development of this little marine creature agrees closely with +that of the Tunicates; but one important feature is added to its +organization--namely, metamerism, segmentally arranged mesoderm. +Amphioxus still possesses neither skull nor vertebræ, neither ribs +nor jaws, and no limbs. But it is a member of the Vertebrata if we +define these as follows: Bilateral symmetrical animals with segmentally +arranged mesoderm, with a chorda dorsalis between the tubular nervous +system and the gut, and with respiratory organs which arise from the +anterior portion of the gut. We do not assume that Amphioxus stands +in the direct ancestral line; it is probably much specialized, partly +degenerated, and represents a side-branch; but it is, nevertheless, +the only creature, hitherto known, which satisfactorily connects the +Vertebrata with their invertebrate ancestors. Many other efforts have +been made to solve the mystery of the origin of the Vertebrata--all +less satisfactory than the present suggestion, or even absolutely +futile. This remark applies especially to the attempts to derive them +from either Articulata or Echinoderms. The other great and highly +developed phylum, the Mollusca, is quite out of the question. We have +to go back to a level at which all these principal phyla meet, and +there we find the Vermalia, the lower of which alone permit connection +in an upward direction with the higher phyla. + + ANCESTRAL TREE OF THE VERTEBRATA. + + _Abridged from 'Systemat. Phylogenie,' § 15._ + + Names underlined refer to hypothetical groups. + + _Mammalia_ + _Aves_ | + | _Reptilia_ | + | | | + +----------------+ | + | | + +--------------+ + | + _Proreptilia_ + | _Amphibia_ + _Pisces_ | | + | | +----------+ + | | | + | | | _Dipnoi_ + | _Stegocephali_ | + | | | + | +---------------+ + | | + +---------------+ + | _Cyclostomata_ + _Proselachii_ | + | | + _Tunicata_ | +--------+ + | | | + | *_Archicrania_* + | | _Acrania_ + | | | + | *_Prospondylia_*------+ + | | + +----------+ | + | | + *_Prochordonia_* + + +11. Stage of _Cyclostomata_. This now small group of Lampreys and +Hagfishes represents the lowest Craniota; and although much specialized +as a side-branch of the main-stem from which the other Craniota have +sprung, they give us an idea of what the direct ancestors of the latter +must have been like:--still without visceral arches, without jaws and +without paired limbs; with a persistent pronephros; the ear with one +semicircular canal only; mouth suctorial; cranium very primitive; +and the metamerism of the vertebral column indicated only by little +blocks of cartilage in the perichordal sheath. Such creatures must +have existed at least as early as the Lower Silurian epoch; but until +1890 fossil Cyclostomes were unknown. Their life in the mud, or as +endoparasites of fishes, coupled with their soft structure, makes them +very unfit for preservation. This gives all the greater importance to +Traquair's discovery, in 1890, of many little creatures, called by him +_Palæospondylus gunni_, in the Old Red Sandstone of Caithness, which +seem to be very closely allied to Cyclostomata. + +12. The _Elasmobranchi_ (sharks and skates), with their immediate +forerunners, the Acanthodi of the Devonian and Carboniferous age, +are the first typical fishes. That they existed as far back as the +Silurian age is proved by many enamelled spines of the dermal armour, +chiefly from the dorsal fins. This higher stage is characterized by the +possession of typical jaws, by visceral or gill-bearing arches, and by +two pairs of limbs. None of the Elasmobranchs, fossil or recent, stands +in the direct ancestral line; but they are the lowest Gnathostomata, +jaw-and-limb-possessing creatures, known. + +13. Closely connected with the Elasmobranchs in a wider sense are the +_Crossopterygii_, which begin in the Devonian age as a large group, but +have left only two survivals, the African Polypterus and Calamoichthys. +They are possessed of dermal bones and other ossifications, and are +characterized by their lobate paired fins, which have a thick axis +beset with biserial fin rays. Their gill-clefts are covered by an +operculum, and they have a well-developed air-bladder. Whilst they +are in many respects more highly developed than the Elasmobranchs, +and are intimately connected with the typical Ganoids and other +bony fishes (all of which form a great, manifold side-branch of the +general vertebrate stem), they stand in many other respects (notably, +the structure of the paired fins, the vertebral column, and the +air-bladder) nearer the main-stem of our own ancestral line. + +14. This is shown by their intimate relation to the _Dipnoi_, which +are still represented by the Australian, African, and South American +mud-fishes: Ceratodus, Protopterus, and Lepidosiren. The genus +Ceratodus existed in the Upper Trias, whence various other unmistakably +dipnoous forms lead down through the Carboniferous (_e.g._, Ctenodus) +to the Devonian strata--_e.g._, Dipterus. They are characterized as +follows: The paired fins still retain the archipterygial form (namely, +one axis with biserial rays); the heart is already trilocular, and +receives blood which is mixed arterial and venous, owing to the gills +being retained, while the air-bladder has been modified into a lung. In +fact, the generalized Dipnoi form the actual link between fishes and +_Amphibia_. + +15. _Amphibia._ The earliest amphibian fossils occur in +the Carboniferous strata. They alone--the Stegocephali or +Phractamphibia--stand in the ancestral line, while the Lissamphibia, to +which all the recent forms belong, are side-branches. The Stegocephali +are the earliest Tetrapoda, the archipterygial paired fins having been +transformed into the pentadactyle fore and hind limbs, which are so +characteristic of all the higher Vertebrata. The cranium is roofed +over by dermal bones, of which, besides others, supra-occipitals, +supra-orbitals, and supra-temporals are always present. The lowest +members (Branchiosauri) still retained gills besides the lungs, while +others (Microsauri) have lost the gills. Be it remembered that all +the recent Amphibia still undergo the same metamorphosis during their +ontogenetic development. + +In the very important Temnospondyli, a subgroup of the +Stegocephali--_e.g._, Trimerorhachis of the Lower Red Sandstone or +Lower Permian--the component cartilaginous or bony units which compose +the vertebræ still remained in a separate, unfused state, showing at +the same time an arrangement whence has arisen that which is typical +of the Amniota. The same applies to the limbs and their girdles. In +fact, the Stegocephali, taken as a whole, lead imperceptibly to the +_Proreptilia_. + +16. _Proreptilia_ are represented by the Permian genera Eryops and +Cricotus. Until quite recently these and many other fossils from +the Carboniferous strata were looked upon as Amphibia, while many +undoubted fossil Amphibia were mistaken for reptiles, as indicated by +the frequent termination '-saurus' in their names. + +The nearest living representative of these extinct Proreptilia is +the New Zealand reptile Hatteria, or Sphenodon, close relations +of which are known from the Upper Trias; while others--_e.g._, +Palæohatteria--have been discovered in the Permian. Anyhow, Sphenodon +is the reptile which stands nearest to the main stem of our ancestry. + +The most important characteristics of the Reptilia, which mark a higher +stage or level, are (1) The entire suppression of the gills--although +during the embryonic development the gill-clefts still appear in all +reptiles, birds, and mammals; (2) The development of an amnion and an +allantois, both for the embryonic life only, but so characteristic +that all these animals are comprised under the name of Amniota; +(3) The articulation of the skull with the first neck vertebræ by +well-developed condyles, either single (really triple) or double (such +a condylar arrangement begins with the Amphibia, but only the two +lateral condyles are developed, while the middle portion, belonging to +the basi-occipital element, remains rudimentary[21]); (4) The formation +of centra, or bodies of the vertebræ, mainly by a ventral pair of the +original quadruple constituents, or arcualia. + + [21] Similar conditions seem to have prevailed among the Proreptilia; + but in those of their descendants which have specialized into Reptiles + and Birds the basi-occipital element becomes more and more predominant + in that formation which ultimately leads to the apparently single + condyle. Hence it is misleading to divide the Tetrapoda into the two + main groups of Amphi-and Mono-condylia, and therefrom to conclude that + the two-condyled Mammalia are more closely related to the likewise + amphicondylous Amphibia than to the so-called monocondylous Reptiles. + +17. Between the Proreptilia and the Mammalia, which latter occur in +the Upper Triassic epoch, we have necessarily to intercalate a group +of very low reptiles, which are still so generalized that their +descendants could branch off either into the Reptilia proper or into +the Mammalia. The changes concerned chiefly the brain and the heart; +of the skeleton, the skull and the pelvis; and, of the tegumentary +structures, the formation of a hairy covering. Many such creatures +existed in the Triassic epoch--namely, the _Theromorpha_--some of which +indeed possess so many characteristics which otherwise occur in the +Mammalia only, that these creatures have been termed _Sauro-Mammalia_. +However, it has to be emphasized that none of the Theromorpha hitherto +discovered fulfils all the requirements which would entitle them to +this important linking position. They only give us an approximate idea +of what this link was like. + +18. Stage of the _Promammalia_, or _Prototheria_. The only surviving +members are the famous duck-bill, Ornithorhynchus, and the spiny +ant-eaters, Echidna and Proechidna, of the Australian region. These +few genera, however, differ so much from one another in various +important respects that they cannot but be remnants of an originally +much larger group. Indeed, many fossils from the Upper Triassic and +from the Jurassic strata have without much doubt to be referred to the +Prototheria. The Prototheria are typical mammals, because they possess +the following characteristics: The heart is completely quadrilocular; +the blood is warm, and its red corpuscles have, owing to the loss +of their nucleus, been modified from biconvex into biconcave discs; +they have a hairy coat and sweat glands, and two occipital condyles; +the ilio-sacral connection is preacetabular; the ankle-joint is +cruro-tarsal; the quadrate bone of the Reptilia has ceased to carry the +under jaw, which now articulates directly with the squamosal portion +of the skull. Their low position is shown by the retention of the +following reptilian features: Complete coracoid bones and a T-shaped +interclavicle; a cloaca, or common chamber for the passage of the +fæces, the genital and the urinary products; they are still oviparous; +the embryo develops without a chorion, and is therefore not nourished +through a placenta. Even the milk glands, which are absolutely +peculiar to the Mammalia, are still in a very primitive stage, and do +not yet produce milk proper; and there is only a temporary shallow +marsupium. + +19. Stage of _Metatheria_, or _Marsupialia_, are direct descendants of +Prototheria; but they show higher development by the reduction of the +coracoid bones and the interclavicle. The original cloaca is divided +into a rectal chamber and a uro-genital sinus, completely separated, +at least in the males; they are viviparous; the young are received +into a permanent marsupium, in the walls of which are formed typical +milk glands and nipples, but the embryo is still devoid of a placenta, +although some recent marsupials show indications of such an organ. The +corpus callosum in the brain is still very weak. + +Most of the marsupials are extinct. They occur from the Upper Trias +onwards, and had in the Jurassic epoch attained a wide distribution +both in Europe and in America. Since the Tertiary epoch they have +been restricted to America and to the Australian region, and are now +represented by about 150 species. + +20. Stage of _Prochoriata_, or early _Placentalia_: a further +development of the Metatheria by the development of a placenta, loss +of the marsupium and the marsupial bones, complete division by the +perineum of the anal and uro-genital chambers, stronger development of +the corpus callosum, or chief commissure of the two hemispheres of the +brain. + +Placentalia must have come into existence during the Cretaceous +epoch. Up to that time all the Mammalia seem to have belonged to +either Prototheria or to Metatheria; but in the early Eocene we can +distinguish the main groups of Placentalia--namely, (1) Trogontia, now +represented by the rodents; (2) Edentata, or sloths, armadilloes, etc.; +(3) Carnassia, or Insectivora and Carnivora; (4) Chiroptera, or bats; +(5) Cetomorpha, or whales and dugongs; (6) Ungulata; (7) Primates. +Of these groups, the first and second, third and fourth, fifth and +sixth, can perhaps, to judge from palæontological evidence, be combined +into three greater groups, as indicated by the fossil Esthonychida, +Ictopsida, and Condylarthra, in addition to the ancestral Primates, +or Lemuravida, as the fourth large branch of the ancestral-tree where +this has reached the placental level. Among none of the first three +branches can we look for the ancestors of the Primates. The Lemuravida, +therefore, represent a branch equivalent to the three other branches. + +21. Stage of _Lemures_, or _Prosimiæ_, comprising the older members of +the Primates, consequently approaching most nearly to the Lemuravida. +The limbs are modified into pentadactyle hands and feet of the arboreal +type, and are protected by nails. The dentition is of the frugivorous +or omnivorous type, with an originally complete series of teeth, with +milk teeth and with permanent. The orbit is surrounded by a complete +bony ring, posteriorly by a fronto-jugal arch, but still widely +communicating with the temporal fossa. The placenta is diffuse and +non-deciduous. + + ANCESTRAL TREE OF THE MAMMALIA. + + _'Systematische Phylogenie,' § 386._ + + _Perissodactyla_ _Homo_ _Carnivora_ + | (_Litopterna_) | | _Pinnipedia_ + | | | | | + +-------+ _Anthropoidae_ +------+ + _Artiodactyla_ | | | + | | | _Carnassia_ + +----------+ _Catarhinæ_ | + | | _Chiroptera_ | + _Proboscidea_ | | | _Insectivora_ | + | | _Platyrhinæ_ | | | + (_Amblypoda_) | | | | +-------+ + | | | | | | _Rodentia_ + +-------+ | _Simiæ_ +-------+ | + | | | | (_Tillodontia_) + +--+ | | | + _Cetacea_ | | | _Trogontia_ + | _Sirenia_ | _Lemures_ _*Ictopsales*_ | _Edentata_ + | | | | | | | + _Cetomorpha_ | _Hyracoidea_ | | _*Esthonychales*_ + | | | | | | + +---_?_---+------+ | | | + | _*Lemuravidæ*_ | | + _*Condylarthrales*_ | +-------+ | + | | | | + +--------Eutheria s. Placentalia------------------+ + | + | _Marsupialia polyprotodontia_ + _Marsupialia diprotodontia_ | | + | | | + +-------------Metatheria--------------+ + | + | _Monotremata_ + | | (_Allotheria_) + | | | + | +-----------------+ + | | + Prototheria-----+ + | + | + _*Hypotheria s.*_ _*Promammalia*_ + + _Names in brackets indicate extinct groups. + Names *underlined* indicate hypothetical groups or combinations._ + +22. Stage of _Simiæ_. Orbit completely separated from the temporal +fossa by an inward extension of the frontal and malar bones meeting the +alisphenoid. Placenta consolidated into a disc, and with a maternal +deciduous portion. Mammæ pectoral only. The dental formula is 2.1.3.3. +All the fingers and toes are protected by flat nails. The tail is long. +The American prehensile-tailed monkeys are a lower side-branch. + +23. Stage of _Catarrhinæ Cercopithecidæ_. The dental formula is +2.1.2.3, owing to the loss of one pair of premolars in each jaw. +The frontal and alisphenoid bones are in contact, separating the +parietal from the malar bone; this feature is correlated with the +enlarged brain. The internarial septum is narrow, and the nostrils +look forwards and downwards instead of sidewards--hence the term +'Catarrhinæ.' The external auditory meatus is long and bony. The tail +is long, with the exception of _Macacus inuus_. The body is covered +with a thick coat of furry hair. Catarrhine monkeys have existed, we +know with certainty, since the Miocene. + +24. Stage of _Catarrhinæ Anthropoidæ_, or _Apes_. Now represented by +the large apes--namely, the Hylobates or gibbon of South-Eastern Asia, +_Simia satyrus_, the orang-utan of Sumatra and Borneo, _Troglodytes +gorilla_, _T. niger_ and _T. calvus_, the gorilla and the chimpanzees +from Western Equatorial Africa. Of fossils are to be mentioned +Pliopithecus and Dryopithecus from European Miocene, and _Troglodytes +sivalensis_ from the Pliocene of the Punjaub. The tail is reduced +to a few caudal vertebræ, which are transformed into a coccyx, not +visible externally; but in the embryos of apes and man the tail is +still a conspicuous feature. The walk is semierect; in adaptation +to the prevailing arboreal life, the arms are longer than the legs. +The hair of the body is considerably more scanty than in the tailed +monkeys. _Troglodytes calvus_, a species or variety of chimpanzee, is +bald-headed. None of the recent genera of apes can lay claim to a place +in the ancestry of mankind. + +25. Stage of _Pithecanthropi_. Hitherto the only known representative +is _Pithecanthropus erectus_, from the Upper Pliocene of Java. In +adaptation to a more erect gait, the legs have become stronger and the +hind-hand has been turned into a flat-soled walking 'foot.' The brain +is considerably enlarged. Presumably it is still devoid of so-called +articulate speech; this is indicated by the fact that children have +to learn the language of their parents, and by the circumstance that +comparative philology declares it impossible to reduce the chief human +languages to anything like one common origin. + +26. _Man._ Known with certainty to have existed as an implement-using +creature in the last Glacial epoch. His probable origin cannot, +therefore, have been later than the beginning of the Plistocene. The +place of origin was probably somewhere in Southern Asia. + +Whilst we have to admit that there are great defects in the older +(invertebrate) portion of our pedigree, we have all the more reason to +be satisfied with the positive results of our investigation of the more +recent (vertebrate) part of it. All modern researches have confirmed +the views of Lamarck, Darwin, and Huxley, and they allow of no doubt +that the nearest vertebrate ancestors of mankind were a series of +Tertiary Primates. + +Particularly valuable are the admirable attempts of the two zoologists, +Paul and Fritz Sarasin,[22] to throw light upon the human phylogeny by +painstaking comparison of all the skeletal parts of man with those of +the anthropoid apes. They have shown that among the lower races of man +the primitive Veddahs of Ceylon approach the apes most nearly, and that +among the latter the chimpanzee stands nearest to man. + + [22] 'Ergebnisse naturwissenschaftlicher Forschungen auf Ceylon,' vols. + 4 and 5. (With an atlas of 84 plates; 1893.) + +The direct descent of man from some extinct ape-like form is now beyond +doubt, and admits of being traced much more clearly than the origin +of many another mammalian order. The pedigrees of the Elephants, the +Sirenia, the Cetacea, and, above all, of the Edentata, for example, +are much more obscure and difficult to explain. In many parts of their +organization--for example, in the number and structure of his five +digits and toes--man and monkeys have remained much more primitive than +most of the Ungulata. + +The immense significance of this positive knowledge of the origin of +man from some Primate does not require to be enforced. Its bearing +upon the highest questions of philosophy cannot be exaggerated. Among +modern philosophers no one has perceived this more deeply than Herbert +Spencer.[23] He is one of those older thinkers who before Darwin were +convinced that the theory of development is the only way to solve +the 'enigma of the world.' Spencer is also the champion of those +evolutionists who lay the greatest weight upon _progressive heredity_, +or the much combated _heredity of acquired characters_. From the first +he has severely attacked and criticised the theories of Weismann, who +denies this most important factor of phylogeny, and would explain +the whole of transformism by the 'all-sufficiency of selection.' In +England the theories of Weismann were received with enthusiastic +acclamation, much more so than on the Continent, and they were called +'Neo-Darwinism,' in opposition to the older conception of Evolution, +or 'Neo-Lamarckism.' Neither of those expressions is correct. Darwin +himself was convinced of the fundamental importance of progressive +heredity quite as much as his great predecessor Lamarck; as were also +Huxley and Spencer. + + [23] 'Principles of Biology': 'The Factors of Organic Evolution'; 'The + Inadequacy of Natural Selection.' + +Three times I had the good fortune to visit Darwin at Down, and on each +occasion we discussed this fundamental question in complete harmony. +I agree with Spencer in the conviction that progressive heredity is +an indispensable factor in every true monistic theory of Evolution, +and that it is one of its most important elements. If one denies with +Weismann the heredity of acquired characters, then it becomes necessary +to have recourse to purely mystical qualities of germ-plasm. I am of +the opinion of Spencer, that in that case it would be better to accept +a mysterious creation of all the various species as described in the +Mosaic account. + +If we look at the results of modern anthropogeny from the highest point +of view, and compare all its empirical arguments, we are justified in +affirming that _the descent of man from an extinct Tertiary series of +Primates is not a vague hypothesis, but an historical fact_. + +Of course, this fact cannot be proved _exactly_. We cannot explain all +the innumerable physical and chemical processes, all the physiological +mutations, which have led during untold millions of years from the +simplest Monera and from the unicellular Protista upwards to the +chimpanzee and to man. But the same consideration applies to all +historical facts. We all believe that Aristotle, Cæsar, and King Alfred +did live; but it is impossible to give a proof within the meaning of +modern exact science. We believe firmly in the former existence of +these and other great heroes of thought, because we know well the works +they have left behind them, and we see their effects in the history +of human culture. These indirect arguments do not furnish stronger +evidence than those of our history as vertebrates. We know of many +Jurassic mammals only a single bone, the under jaw. We all believe that +these mammals possessed also an upper jaw, a skull, and other bones. +But the so-called 'exact school,' which regards the transformation of +species as a hypothesis not proven, must suppose that the mandibula was +the only bone in the body of these curious animals. + +Looking forward to the twentieth century, I am convinced that it will +universally accept our theory of descent, and that future science +will regard it as the greatest advance made in our time. I have no +doubt that the influence of the study of anthropogeny upon all other +branches of science will be fruitful and auspicious. The work done in +the present century by Lamarck and Darwin will in all future times be +considered one of the greatest conquests made by thinking man. + + EVOLUTIONARY STAGES OF THE PRINCIPAL GROUPS OF VERTEBRATA.[24] + + STAGES OF THE CLASSES. STAGES OF THE HEART. + PAIRED LIMBS. + + { 1. _Acrania._ I. _Leptocardia._ + I. _Adactylia_ { Cold-blooded; heart + s. _Impinnata_. { with one chamber; + Without jaws { without lungs. + and limbs. { + { 2. _Cyclostomata._ } II. _Ichthyocardia._ + } Cold-blooded; heart + } two-chambered, with + } one atrium and one + } ventricle; heart + } containing venous + } blood only; without + II. _Polydactylia_ { 3. _Pisces._ } lungs. + s. _Pinnata_. { + With two { } III. _Amphicardia._ + pairs of fins. { 4. _Dipnoi._ } Cold-blooded; heart + } with three complete + } chambers, namely, with + } two atria and one + } ventricle, or (Reptilia) + { 5. _Amphibia._ } two ventricles with still + { } incomplete septum; heart + { } containing mixed venous + { } and arterialized + III. _Pentadactylia_ { 6. _Reptilia._ } blood; with lungs. + s. _Tetrapoda_. { + With two pairs { { IV. _Thermocardia._ + of pentadactyle { { Warm-blooded; heart + limbs (unless { 7. _Aves._ { with four complete + they have { { chambers, namely, two + been lost by { { auricles and two + reduction). { { ventricles; right half + { { of the heart with venous, + { { left half with + { { arterialized, blood; with + { 8. _Mammalia._ { lungs. + + + [24] Abridged from Haeckel's 'Systematische Phylogenie der + Vertebraten,' § 14. + + + + + BIOGRAPHICAL SKETCHES + + +JEAN BAPTISTE DE MONET, CHEVALIER DE LAMARCK, was born on +August 1, 1744, in Picardy, where his father owned land. Originally +educated for the Church, he soon enlisted, and distinguished himself +in active service. Owing to an accident affecting his health, the +young Lieutenant gave up the military career, and, without means, +studied medicine and natural sciences at Paris. In 1778 appeared his +'Flore française.' In 1793 he was appointed to a Chair of Zoology at +the newly-formed Musée d'Histoire Naturelle. He had the misfortune to +become gradually blind, and the last years of his life were spent amid +straitened circumstances. He died in 1829. + +In 1794 Lamarck divided the whole animal kingdom into vertebrate and +invertebrate animals, and founded successively the groups of Crustacea, +Arachnida, Annelida, and Radiata. Between 1816 and 1822 he published +his celebrated 'Histoire naturelle des Animaux sans Vertèbres.' + +His most famous work is the 'Philosophie zoologique,' 1809. + +Assuming the spontaneous origin of life, he propounded the doctrine +that all animals and plants have arisen from low forms through +incessant modifications and changes. In this respect he was in absolute +opposition to Cuvier, who upheld the immutability of species, and did +his best by absolute silence to suppress the spread of the new doctrine. + +Lamarck has explained his views of transformism chiefly in the seventh +chapter of the first volume of his 'Philosophie zoologique.' + +Organisms strive to accommodate or adapt themselves to new +circumstances, or to satisfy new requirements--_e.g._, climate, mode +of procuring food, escape from enemies. The continued function of +parts of an organism changes the old and produces new organs. The +acquirements are inherited by the offspring, and thus are produced the +more complicated from simpler organisms. Continued disuse brings about +degeneration and ultimate loss of an organ. + +Lamarck consequently sees in the adaptability, or power of adaptation, +which he assumes for all living matter the ultimate cause of variation; +and, as he was certainly the first to point out that acquired +characters are inherited by the progeny, he has given a working +explanation of Evolution. + +But his doctrine did not spread--partly because he was misunderstood. +His theory, that a new want, by making itself felt, exacts from the +animal new exertions, perhaps from parts hitherto not used, until the +want is satisfied--this way of putting it sounds too teleological +to explain the yearned-for change in a mechanical or natural way. +Moreover, many of his examples lacked the exact basis of experiment +and observation necessary for their acceptance. Witness that of the +neck of the giraffe,--a never-failing source of ridicule to men who +cannot see the deeper purpose underlying the well-meant attempt at +an explanation, which failed from want of complete knowledge of the +intricate circumstances. + +However, the theory of transformism was, so to speak, in the air; +and various authors have written on the subject, filling the gap +between Lamarck and Darwin, especially Goethe, Treviranus, Leopold +von Buch, and Herbert Spencer. But it is Darwin's immortal merit to +have opened our eyes by his theory of natural selection, which is, at +least, the first attempt to explain some of the causes and incidents +of organic Evolution in a natural mechanical way. Moreover, he was +the first clearly to express the fundamental principles of the theory +of descent, to elaborate what had been at best a general sketch of an +ill-defined problem, and to enter into detail, supported by a host +of painstaking observations, the making of which had taken him half a +lifetime. Darwin, without going further than cursorily into the causes +of variation, argued as follows: We know that variations do occur +in every kind of living creatures. Some of these variations lead to +something, while others do not. An enormously greater number of animals +and plants are born than reach maturity and can in their turn continue +the race. What is the regulating factor? His answer is, The struggle +for existence--in other words, the weeding out of the less fit, or +rather of the owners of those variations which are not so well adapted +to their surroundings. + +For 'adapted' we had better read 'adaptable,' because a variation which +does not answer, which cannot be made use of, or, still more notably, +is a hindrance or disadvantage, does not become an adapted feature. +There is often a confusion between adaptation as an accomplished +fact, a feature, or resultant condition, and adaptation as the mode +of fitting the organism to, or making the best of, the prevailing +surroundings or circumstances. + +ÉTIENNE GEOFFROY SAINT-HILAIRE was born in 1772 at Étampes, +Seine-et-Oise. He was originally brought up for the Church; but when +already ordained he attended lectures on natural science and medicine +in Paris. He managed to get the place of assistant in the Musée +d'Histoire Naturelle; he became Professor of Zoology in 1793, and took +the opportunity of encouraging young Cuvier. Later he became Professor +of Zoology of the Faculté des Sciences, and in 1818 he published his +remarkable 'Philosophie anatomique.' He died in 1844. + +He had conceived the 'unity of organic composition,' meaning that there +is only one plan of construction,--the same principle, but varied in +its accessory parts. In 1830, when Geoffroy proceeded to apply to the +Invertebrata his views as to the uniformity of animal composition, +he found a vigorous opponent in Cuvier. Geoffroy, like Goethe, held +that there is in Nature a law of compensation, or balancing of growth, +so that if one organ take on an excess of development, it is at the +expense of another part; and he maintained that, since Nature takes no +sudden leaps, even organs which are superfluous in any given species, +if they have played an important part in other species of the same +family, are retained as rudiments, which testify to the permanence +of the general plan of creation. It was his conviction that, owing +to the conditions of life, the same forms had _not_ been perpetuated +since the origin of all things, although it was not his belief that +existing species were becoming modified. Cuvier, on the other hand, +maintained the absolute invariability of species, which, he declared, +had been created with regard to the circumstances in which they were +placed, each organ contrived with a view to the function it had +to fulfil,--thus putting the effect for the cause ('Encyclopædia +Britannica,' 9th edition, vol. xxi., p. 171). + +GEORGE CUVIER was born in 1769 at Montbéliard, in the department of +Doubs, which at that time belonged to Württemberg. He was educated at +Stuttgart, and studied political economy. While acting as private tutor +to a French family in France he followed his favourite pursuit, the +study of natural sciences. Geoffroy Saint-Hilaire heard of him, and +appointed him assistant in the department of comparative anatomy in the +Musée d'Histoire Naturelle. In 1799 he was elected Professor of Natural +History at the Collège de France, and soon after he became Perpetual +Secretary of the Institut National. In 1831, a year before his death, +Louis Philippe raised him to the rank of a peer of France. + +Cuvier was the first to indicate the true principle upon which the +natural classification of animals should be based--namely, their +structure. It is the study of the anatomy of the creatures and their +comparison which affords the only sound basis of a classification. +The work which had the greatest influence upon the scientific public +is his 'Règne animal distribué d'après son Organisation,' 1817. The +system which he propounded in this book gradually came to have almost +world-wide fame, and, in spite of its many obvious deficiencies, still +lingers in some of our most recent text-books. + +A standard work is his 'Leçons d'Anatomie comparée,' and, in truth, he +is the founder of that kind of comparative anatomy which was brought +to such a high state by his pupil, the late Sir Richard Owen. Cuvier +discovered the law of 'correlation of growth,' and was the first to +apply this law to the reconstruction of animals from fragments: see his +monumental work entitled 'Recherches sur les Ossemens fossiles,' 1812. + +Cuvier, however, as a strict matter-of-fact man, was incapable of +appreciating the speculative conclusions which were drawn by his +contemporaries Saint-Hilaire and Lamarck. On the contrary, he firmly +stuck to the doctrine of the immutability of species; and, in order to +account for the existence of animals whose kind exists no longer, he +invented the famous doctrine of successive cataclysms. + +KARL ERNST VON BAER was born in 1792 in Esthonia, studied at Dorpat +and then at Würzburg, where Döllinger introduced him to comparative +anatomy. For a few years he was a _Privat-docent_ at Berlin; then he +went to Königsberg as Professor of Zoology and Embryology. In 1834 +he became an Academician at St. Petersburg, where for many years he +was occupied with the most varied studies, chiefly geographical and +ethnological. The last years of his long, active life he spent in +contemplative retirement on his paternal estate, and he died at Dorpat +in 1876. + +While still at Würzburg he induced his friend Pander, a young man +of means, to study the development of the chick; and Pander was the +first to start the theory of the germinal layers from which all the +organs arise. Baer, however, continued these researches in Königsberg, +and after nine years' labour produced his epoch-making work, 'Ueber +Entwicklungsgeschichte der Thiere: Beobachtung und Reflexion,' +Königsberg, 1828. Nine years later he completed the second volume. +He established upon a firm basis the theory of the germinal layers, +and by further 'reflexions' arrived at the elucidation of some of the +most fundamental laws of biology. For example, in the first volume +he made the following prophetic statement: 'Perhaps all animals are +alike, and nothing but hollow globes at their earliest developmental +beginning. The farther back we trace their development, the more +resemblance we find in the most different creatures. And this leads to +the question whether at the beginning of their development all animals +are essentially alike, and referable to one common ancestral form. +Considering that the "germ" (which at a certain stage appears in the +shape of a hollow globe or bag) is the undeveloped animal itself, we +are not without reason for assuming that the common fundamental form is +that of a simple vesicle, from which every animal is evolved, not only +theoretically, but historically.' + +This statement is all the more wonderful when we consider that the +cells, the all-composing individual units, were not discovered until +ten years later. + +In 1829 Baer discovered the human egg, and later the chorda dorsalis. +In an address delivered in 1834, entitled 'The Most Universal Law +of Nature in all Development,' he explained that only from a most +superficial point of view can the various species be looked upon as +permanent and immutable types; that, on the contrary, they can be +nothing but passing stages, or series of stages, of development, which +have been evolved by transformation out of common ancestral forms. + +JOHANNES MUELLER, born at Coblenz in 1801, established himself +as _Privat-docent_ at Bonn, where in 1830 he became Professor of +Physiology. In 1833 he accepted the Chair of Anatomy and Physiology at +Berlin, where he died in 1858. + +He was one of the most distinguished physiologists and comparative +anatomists. By summarizing the labours and discoveries already made in +the field of physiology, by reducing them to order, and abstracting the +general principles, he became the founder of modern physiology. But +he was scarcely less distinguished by his researches in comparative +anatomy. His 'Vergleichende Anatomie der Myxinoiden,' in _Abhandlungen +der Berliner Akademie_, 1835-45, and 'Ueber die Grenzen der Ganoiden' +(_ibid._, 1846), are standard works of lasting value. + +Mueller exercised a stimulative influence as a teacher. Many well-known +men--such as Helmholtz, Gegenbaur, Bruecke the physiologist, Guenther +the zoologist, Virchow the pathologist, Koelliker and Haeckel--have +been his pupils. + +RUDOLPH VIRCHOW was born in 1821 at Schievelbein, a small +town in Eastern Pomerania. He studied medicine in Berlin as a pupil +of Johannes Mueller, and went in 1849 to Würzburg, where, under the +influence of Koelliker, and Leydig the pathologist, he laid the +foundation of an entirely new branch of medical science--that of +'cellular pathology.' Since 1856 he has filled the principal Chair of +Pathology at Berlin. In 1892 he received the Copley medal of the Royal +Society. + +'His contributions to the study of morbid anatomy have thrown light +upon the diseases of every part of the body; but the broad and +philosophical view he has taken of the processes of pathology has +done more than his most brilliant observations to make the science of +disease. + +'In pathology, strictly so called, his two great achievements--the +detection of the cellular activity which lies at the bottom of +all morbid as well as normal physiological processes, and the +classification of the important group of new growths on a natural +histological basis--have each of them not only made an epoch in +medicine, but have also been the occasion of fresh extension of science +by other labourers' (Proc. Royal Soc., 1892). + +Virchow has not confined himself to medicine. He takes the keenest +interest in anthropology and ethnology, on which subjects he has +contributed many papers. Together with his colleagues Helmholtz the +physicist, and Du Bois Reymond the physiologist, he has taken a leading +place in the spreading of natural science; but, unfortunately, he +did not take to the doctrine of Evolution, and for the last thirty +years has been its declared antagonist, rarely missing an opportunity +of denouncing everything but descriptive anatomy and zoology as the +unsound speculations of dreamers. This has on more than one occasion +brought him into sharp conflict with Haeckel. His activity is +astonishing, especially if it be remembered that Virchow has for many +years been one of the most conspicuous leaders of the Progressists and +Radicals in the German Parliament and Berlin town-council. + +EDWARD DRINKER COPE was born at Philadelphia, Pa. After studying at +several Continental Universities, especially at Heidelberg, he became +first Professor of Natural Science at Haverford College, and later +Professor of Geology and Mineralogy. He died at an early age in 1897. +As a member of various geological expeditions and other surveys, he +explored chiefly Kansas, Wyoming, and Colorado; and he published many +most suggestive papers on the fossil vertebrate fauna of North America, +and on classification especially of Amphibia and Reptiles. + +Among works of a more general philosophical scope may be mentioned 'The +Origin of the Fittest,' 1887, and his latest work, 'The Primary Factors +of Organic Evolution,' 1896. + +ALBERT VON KOELLIKER, born in 1817, became Professor of Anatomy at +Würzburg. His earlier studies and discoveries contributed considerably +to the systematic development of the cell theory. In 1844 he observed +the division and further multiplication of the original egg cell. Next +year he showed the continuity between nerve cells and nerve fibres in +the Vertebrata; later, that the non-striped or smooth muscular tissue +is composed of cellular elements. He demonstrated that the Gregarinæ +are unicellular creatures. In 1852 he went with his younger friend +Gegenbaur to Messina, where he studied especially the development +of the Cephalopoda (cuttlefishes and allies); and he produced a +magnificent work on Alcyonaria, Medusæ, and other allied forms. He +elucidated the development of the vertebral column, especially with +reference to the notochord. + +In 1848 he founded, together with Th. von Siebold, the famous +_Zeitschrift für wissenschaftliche Zoologie_. + +A standard work on mammalian embryology is his 'Entwicklungsgeschichte +des Menschen und der höheren Thiere,' a text-book of which the second +edition appeared in 1879. + +At the anniversary meeting of 1897 he received the Copley medal, the +highest honour which the Royal Society can bestow. + +CARL GEGENBAUR was born on August 21, 1826, in Bavaria. He studied +medicine and kindred subjects in Würzburg, and as a pupil of Johannes +Mueller in Berlin. + +In 1852 he went with Koelliker to Messina to study the structure and +development of the marine fauna. Important papers on Siphonophora, +Echinoderms, Pteropoda, and, later, Hydrozoa and Mollusca, were the +result. Soon after his return he was offered the chair of Anatomy at +Jena, and at this retired spot he produced his most important works, +devoting himself more and more to the study of the Vertebrata. Since +1875 he has held the Chair of Anatomy at Heidelberg. + +In 1859 he published his 'Principles of Comparative Anatomy'; but in +1870 he remodelled it completely, the theory of descent being the +guiding principle. These 'Grundzüge' were followed by a somewhat more +condensed 'Grundriss,' the second edition of which was published +in 1878, and has been translated into French and English. In the +meantime he had broken new ground by the development and treatment of +certain problems concerning the composition and origin of the limbs, +the shoulder-girdle and the skull, researches which are embodied in +his 'Untersuchungen zur vergleichenden Anatomie der Wirbelthiere,' +1864-65-72. + +In 1883 he brought out a text-book on human anatomy. This also marked +a new epoch, because for the first time, not only the nomenclature, +but also the general treatment of human anatomy, was put upon a firm +comparative anatomical basis. The success of this work is indicated by +the fact that it reached the sixth edition in 1897. + +Lastly, in 1898, appeared the first volume of what may be called his +crowning work, 'Vergleichende Anatomie der Wirbelthiere.' + +Gegenbaur is universally recognised, not only as the greatest living +comparative anatomist, but also as the founder of the modern side of +this science, by having based it on the theory of descent. + +In 1896 he received from the Royal Society the Copley medal 'for +his pre-eminence in the science of comparative anatomy or animal +morphology.' + +His marvellously powerful influence as a teacher and investigator has +made Heidelberg a centre whence many pupils have spread his teaching, +and above all his method of research. + +ERNST HEINRICH HAECKEL was born on February 16, 1834, at Potsdam. He +carried out his academical studies alternately at Berlin and Würzburg, +attracted by such men as Johannes Mueller, Koelliker, and Virchow. +For years he was undecided what his career should be, whether that +of botanist, collector, or geographical traveller. Certainly that of +medicine attracted him least, although in deference to his father's +wishes he qualified and settled down for a year's practice in Berlin. +As he himself has told us, he might perhaps have proved rather +successful as a physician, to judge from the fact that he did not lose +a single patient. But 'I had only three patients all told, and the +reason of this is perhaps that I had given on my plate the hours of +consultation as from 5 to 6 _a.m._' + +During the year 1859 he travelled as medical man and artist in Sicily. +In 1861 he was induced by Gegenbaur, whose acquaintance he had made in +Würzburg, to establish himself as a _Privat-docent_ for comparative +anatomy in Jena. And there he has remained ever since, filling the +Chair of Zoology, and having declined several much more tempting offers +from the Universities of Würzburg, Vienna, Strassburg, and Bonn. + +Within one year, 1865, he wrote the two volumes of his 'Generelle +Morphologie der Organismen,' as he himself relates, in order to master +his sorrow over the loss of his first wife. But he broke down, and went +to the Canaries to recruit health and strength. The 'Morphologie,' +which has long been out of print,[25] made scarcely any impression. It +was ignored, probably because he had placed the old-fashioned study of +zoology and morphology upon a thoroughly Darwinistic basis. + +[25] That this great work is now comparatively rare, although still +in the second-hand market, may perhaps be urged in excuse of the +fact of so many attempts made by many authors, both professional and +amateur, to find fault with or to explain the principles of adaptation, +variation, heredity, cænogenesis, phylogeny, etc., in complete +ignorance that all these and many more fundamental questions were fully +discussed more than thirty years ago in the 'Generelle Morphologie.' + +On the advice of his friend Gegenbaur, he gave a more popularly +written abstract of his 'Generelle Morphologie'--in fact, the +substance of a series of his lectures--in the shape of his 'Natürliche +Schöpfungsgeschichte.' This 'History of Natural Creation,' which +in 1898 has reached the ninth edition (first edition translated +into English in 1873), had the desired effect. So also had his +'Anthropogenie oder Entwicklungsgeschichte des Menschen,' the fourth +edition of which appeared in 1891. + +It was a lucky coincidence that Haeckel had just finished his +preliminary academical studies, was entirely at leisure, and +undetermined to which branch of natural science he should devote his +genius, when Darwin's great work was given to the world. Haeckel +embraced the new doctrine fervently, and, as Huxley was doing in +England, he spread it and fought for it with ever-increasing vigour in +Germany. + +With marvellous vigour and quickness of perception he applied the +principles of Evolution or the theory of descent to the whole organic +world, and not only opened entirely new vistas for the study of +morphology, but also worked them out and fixed them. He was the first +to draw up pedigrees of the various larger groups of animals and +plants, filling the gaps by fossils or with hypothetical forms (the +necessary existence of which he arrived at by logical deductions); +and thus he reconstructed the first universal pedigree, a gigantic +ancestral tree, from the simple unicellular Amoeba to Man. Of course +these pedigrees were entirely provisional, as he himself has over and +over again avowed; but they are, nevertheless, the ideal which all +systematists and morphologists working upon the basis of Evolution have +since been seeking to establish. + +Naturally he was vigorously attacked, not only by anti-Darwinians, +or rather anti-Evolutionists, but also by many of those who, having +accepted the principle of transformism, ought to have known better. +Perhaps they thought they did know better. Imperfections or mistakes in +details of the grand attempt,--and these, naturally, were many,--were +singled out as samples of the whole, which was ridiculed as the romance +of a dreamer. + +In the end, however, this hostility, narrow-minded and unfair in +many respects, has done good to the cause. There has arisen an +ever-increasing school of workers in favour of the new doctrine. Owing +to renewed research, criticism, corrections in all directions, we +now know considerably more about natural classification (and this is +pedigree) than when Haeckel first opened out the whole problem. + +Owing to his fearless mode of exposition, regardless of the indignant +wrath which the new doctrine aroused in certain ecclesiastical +quarters, Haeckel bore the brunt of almost endless attacks, and had to +write polemical essays. The result has been that friend and foe alike +are now working on the lines which he has laid down; most of the ideas +which he was the first to conceive, and to formulate by inventing a +scientific terminology for them, have become important branches, or +even disciplines, of the science. + +Most morphologists of the younger generations now take these terms +for granted, without remembering the name of their founder. It is, +therefore, perhaps not quite superfluous to mention some of them: + +_Phylum_, or stem, the sum total of all those organisms which have +probably descended from one common lower form. He distinguished eight +such phyla--Protozoa, Coelenterata, Helminthes or Vermes, Tunicata, +Mollusca, Articulata, and Vertebrata. The phyla are more or less +analogous to 'super-classes,' large branches or 'circles,' or principal +groups of other zoologists. + +_Phylogeny_, the history of the development of these various phyla, +classes, orders, families, and species. + +_Ontogeny_, the history or study of the development of the individual, +generally called embryology. In reality the scope of embryology +is the ontogenetic study of the various species, and this branch +of developmental study alone can be checked by direct, 'exact' +observation, for the simple reason that the individuals alone are +entities, while the species, genera, families, etc., are abstract ideas. + +The _ontogenesis of any given living organism is a short, condensed +recapitulation of its ancestral history or of its phylogenesis_. This +is Haeckel's 'fundamental biogenetic law.' + +A complete proof of the phylogeny of any creature would be given by +the preservation of an unbroken series of all its fossil ancestors. +Such a series will in most cases, for obvious reasons, always remain a +desideratum. In a few cases, however, the desideratum is nearly met: +for example, the ancestral line of the one-toed digitigrade horse from +a four-or five-toed plantigrade and still very generalized Ungulate is +approaching completion. + +Phylogenetic study has to rely upon other help. This is afforded by +comparative anatomy and by the study of ontogeny. If the latter were +a faithful, unbroken recapitulation of all the stages through which +the ancestors have passed, the whole matter would be very simple; but +we know for certain that in the individual development many stages +are left out (or, rather, are hurried through, and are so condensed +by short-cuts being taken that we cannot observe them), while other +features which have been introduced obscure, and occasionally modify +beyond recognition, the original course. + +Again, the sequence of the appearance of the various organs is +frequently upset (_heterochronism_). Some organs are accelerated in +their development, while others, which we know to be phylogenetically +older, are retarded in making their reappearance in the embryo. + +These disturbing or distorting newly introduced features or factors +show themselves chiefly in connection with the embryonic conditions of +growth--for example, yolk-sac, placenta, amnion. They all come within +the category of _cænogenesis_: they are cænogenetic, while the true, +undisturbed recapitulation is _palingenetic_. + +Lastly, some features, so-called rudimentary or vestigial organs, +instead of disappearing, are most tenacious in their recurrence, +while others of originally fundamental importance scarcely leave +recognisable traces, and are, so to speak, only hinted at during the +embryonic growth of the creature we happen to study. Hence arises the +philosophical study of 'Dysteleology.' + +Among other terms invented by Haeckel, and now in general use, are +_Metamere_, _Metamerism_, _Coelom_, _Gonochorism_, _Gastrula_, +_Metazoa_, _Gnathostomata_, _Acrania_, _Craniota_, and _Amniota_. + +Hitherto we have dealt with his general work only, a résumé of which +he gave for many years in a course of thirty lectures before an +audience composed of 'all sorts and conditions of men.' Students of +biology and of medicine side by side with theologians, incipient and +ordained, jurists, political economists, and philosophers, crowded his +lecture-room during the 'seventies to hear the master explaining the +'natural history of creation' or the mysteries of anthropogenesis. +Another course of eighty lectures during the winter semester was, and +still is, devoted to a systematic treatment of zoology, while practical +classes are reserved for the more select. + +His winning personality and fascinating eloquence, combined with a +clear and concise delivery, have gained the enthusiastic admiration of +many a student who went to the quiet University town in order to learn +with his own ears and eyes. + +_List of Separate Publications by Professor Haeckel._ + +'Biologische Studien. I.: Studien ueber die Moneren und andere +Protisten.' Leipzig, 1870 (out of print). He was the first to +make observations on the natural history of the Monera, living +bits of protoplasm, devoid even of a nucleus--_e.g._, _Protogenes +primordialis_, _Protomyxa aurantiaca_. + +'Monographie der Radiolarien.' Berlin, 1862-88. With 171 plates. + +'Entwicklungsgeschichte der Siphonophoren.' Utrecht, 1869. + +'Plankton-Studien. Vergleichende Untersuchungen ueber die Bedeutung und +Zusammensetzung der pelagischen Fauna und Flora.' Jena, 1880. + +'Metagenesis und Hypogenesis von Aurelia aurita.' Jena, 1881. + +'Monographie der Geryoniden oder Ruesselquallen.' Leipzig, 1865. + +'Generelle Morphologie der Organismen.' 2 vols. Berlin, 1866. + +'Anthropogenie oder Entwicklungsgeschichte des Menschen,' 1874; 4th +edition, 1891. + +'Natuerliche Schoepfungs-Geschichte.' 2 vols. Berlin, 1st edition, +1868; 9th edition, 1898. This work has been translated into most +European languages (the first edition in English, under the title +'Natural History of Creation' in 1873; the eighth in 1892). + +'Monographie der Kalkschwaemme.' 3 vols. Berlin, 1872 (out of print). +With the subtitle, 'An Attempt to solve analytically the Problem of +the Origin of Species.' In this work, illustrated by sixty plates, he +showed that the Calcispongia are individually so yielding, so adaptive +to external influences, that it is practically impossible to break up +the whole group into anything like satisfactory species or genera. +According to predilection, we can distinguish either 1 genus with only +3 species, or 3, 21, 43 genera, with 21, 111, 181, or 289 species +respectively. + +In this work, in 1872, Haeckel established the homology of the two +primary layers, ecto- and endoderm, throughout the Metazoa. The attempt +to do the same for the four secondary layers, as made in the second +part of his 'Gastræa-theory,' failed. It caused an enormous amount of +research, hitherto without a satisfactory solution of the problem. + +'Studien zur Gastræa-Theorie.' Jena, 1874. The transformation of +the single primitive egg-cell by cleavage into a globular mass of +cells (Morula)--which latter, becoming hollow (and then known as the +Blastula), turns ultimately by invagination or by delamination into +the Gastrula--is a series of processes which applies to all Metazoa. +The Gastrula is, therefore, the ancestral form of the Metazoa; and the +Gastræa-theory, founded by Haeckel, throws light, on the one hand, upon +the mystery of the phyletic connection of the various animal groups, +while, on the other hand, it connects the Metazoa, or multicellular +organisms, with the lowest Protozoa. We come to this conclusion +becaues the Gastrula arises from and passes through stages which exist as +independent, permanent organisms among the Protozoa. + +Needless to say this Gastræa-theory has been violently attacked in +detail, with the result that various modifications of the Gastrula, +until then undreamed of, have become known. + +'Monographie der Medusen.' Jena, 1879-81. With 72 coloured plates. + +'Reports on the Scientific Results of the Voyage of H.M.S. +_Challenger_.' With 230 plates: + + 1. Deep-sea Medusæ. 1881. + 2. Radiolaria. 1887. + 3. Siphonophoræ. 1888. + 4. Deep-sea Keratosa. 1889. + +A short holiday spent on the coasts of the Red Sea produced the volume +'Arabische Korallen' (Berlin, 1876); and a longer trip to Ceylon has +been described in 'Indische Reisebriefe,' of which the third edition +appeared in 1893. The English translation (1883) is entitled 'A Visit +to Ceylon.' + +'Monism as connecting Religion and Science: the Confession of Faith of +a Man of Science.' 1894. + +Haeckels latest work is the 'Systematische Phylogenie' (Berlin, 1896), +three volumes dealing with Protistæ and Plants, Invertebrata and +Vertebrata. They contain the author's views on the natural system of +the organic world, both living and extinct. Notable in the work are +the many reconstructions of ancestral forms which, provided Evolution +is true, must have existed--hypothetical until they, or something like +them, are found in a fossil state. Everybody who works systematically, +and upon the basis of Evolution, does, sometimes unconsciously, +reconstruct such links, although he may perhaps not see the necessity, +or have the courage to fix his vision, by assigning to it all those +attributes or characters which are indicated by deductions from +comparative anatomy, palæontology, and embryology. + + + + + THEORY OF CELLS. + + +The vegetable cell was discovered by _Schleiden_, Professor of Botany +at Jena, in 1838. Next year _Schwann_ found the animal cell. + +In 1844 _Koelliker_ discovered that the egg cell, by division and +multiplication, becomes an aggregation--a heap of new cells. + +In 1849 _Huxley_ found the two primary layers (observed long before +by _Pander_ and _Baer_ in the chick) also in certain Invertebrata, +the Medusæ; and he called these layers 'ectoderm' and 'endoderm' +respectively. + +In 1851 _Remak_, in his 'Untersuchungen über die Entwicklung der +Thiere,' showed the egg to be a simple cell, and that from it, by +repeated division or multiplication, arise the germinal layers, and +that by differentiation of the cells of these layers are formed all the +tissues of the body. + +_Kowalevsky_, of St. Petersburg, found the two primary germinal layers +also in Worms, Echinoderms, Articulata, and other animals. + +_Haeckel_, in 1872, found the same in the Sponges. He stated that these +two germinal layers occur in all animals, except in the Protozoa; +and that they are homologous, or equivalent, in all the groups of +animals, from the Sponges up to Man. In 1873, in his 'Gastræa-theorie,' +he explained the phylogenetic significance, and tried to show the +homology, of the four secondary germinal layers. + + + + + FACTORS OF EVOLUTION. + + +An organism, as living matter, does not stand in opposition to, +or outside of, the rest of the world. It is part of the world. It +receives matter from its surroundings, and gives some back; therefore +it is influenced by its surroundings. It is acted upon, and it reacts +upon the latter, and if these change (and they are nowhere and never +strictly the same) the organism also _varies_. It _adapts_ itself, and +if it does not, or, rather, cannot, do so, it dies, because it is unfit +to live in the world, or, rather, in those particular surroundings +and conditions in which it happens to be. That organism which yields +most easily, accommodates itself most quickly, has the best chance of +existence--_survival of the fittest_. 'Fitness' in this case does not +mean fitness to live, but rather a particular condition which happens +to fit into the new circumstances. + +Adaptation and variation are simultaneous: they are fundamentally the +same. If there were no adaptability and no variability, those simplest +of organisms which we suppose to have sprung into existence in the +pre-Cambrian period would long ago have ceased to exist. + +It is the physiological momentum which models the organism, and, by +causing its adaptations, has produced its organs by change of function. +Gegenbaur illustrates this most important fundamental truth by an +excellent example. Suppose that, in an absolutely simple organism, all +the parts of its exterior are under the same functional conditions, +so that each part of the surface can take in food, and that this is +digested, assimilated, in the interior. There is, in this condition, +not yet any definite organ. If this organism sinks to the bottom and +becomes sessile, this part is excluded from taking in nourishing +matter, while the opposite surface alone remains, or becomes more, fit +for this function. Thus, a simple variation and adaptation has been +produced, and if the same organism continues in this position, its +bottom cells will estrange themselves from their original function, +while those on the top will convey the food into the interior, where +a cavity will be formed, ultimately with a permanent opening, the +primitive gut and mouth, both very different from the 'foot.' + +Thus, by adaptation and variation the organism acquires new functions, +organs, features, and it gives up and eventually loses others. Its +offspring is like it. Like produces like. This is the principle of +_heredity_. Adaptation, when going on generation after generation on +the same lines in the same direction, becomes continuous, and has an +intensifying, _cumulative_ effect. By always weeding out from a flock +of pigeons those birds which possess more dark feathers than the rest, +we ultimately produce an entirely white race. We hurry on what Nature +does slowly. + +The inheritance of acquired characters becomes very obvious in the +following example: The Monera are the lowest living organisms known; +they consist of a mass of protoplasm, and are still devoid of even +a nucleus. They multiply simply by division; each half is like the +other, and like the parent (which by this process has ceased to exist), +except that each is smaller and has to grow. A certain Moneron, +_Protomyxa aurantiaca_, is orange-coloured, and its offspring is from +the beginning of the same colour, and this colour has been acquired +by that kind of Monera-like protoplasm which thereby has become the +species called Aurantiaca. We have no reason for assuming that there +existed from the beginning of life not only colourless, but also red, +orange, and other kinds of protoplasm. In these simplest of organisms +the whole process of heredity seems very obvious; but in the higher +ones, in those which propagate by eggs, the problem is infinitely +more complicated. It is true that the egg is, strictly, nothing but +a small part of the parental organism, and we know from everyday +experience that this single egg-cell has in it all the attributes and +characteristics of the parent; but these attributes and characteristics +make their appearance successively, just as the egg cell of a chick has +neither wings nor feathers, not even a backbone, but develops these +organs because its parents have them. + +The theory that acquired characters are hereditary has often been +vigorously attacked; but the champions of the negative position have +not given us anything satisfactory instead. They question, also, the +principle of adaptation as a factor in Evolution, and substitute +'variation,' coupled with 'natural selection.' + +They point to Darwin's argument: (1) It is a fact that animals and +plants produce a much greater number of young than in their turn grow +up to propagate the race; (2) no two of the frequently many individuals +of the same breed are exactly alike, although the differences may be +hidden to our perception (this is quite true, because no two entities +can live in absolutely the same place and conditions); (3) through +heredity the offspring takes over the faculties and features of the +parents; (4) what decides which of the many individuals (each one +possessing some aberration or variation) are to live and to propagate +the race?--obviously those individual variations which happen to make +the lucky possessors most fit for the struggle for life. + +So far, well; but the 'Neo-Darwinians' imagine that 'adaptation' +is not the cause, but the result, the effect, of the formation of +species. According to them, the species are neither adapted by, nor do +they adapt themselves to, their surroundings. Adaptation is to them +an accomplished fact, a condition which a species happens to be in +because its particular variation is the one which, to the exclusion of +others, suits or fits into its surroundings. Such a view simply takes +variation for granted, and stipulates it as a something _a priori_, +without raising the further necessary question, why there should be +any variations at all. Why, indeed, unless they are caused by external +influences? Haeckel elucidated this by the conception of adaptation as +explained in the foregoing pages. + +These and kindred speculations have produced some rather curious +discussions, which not infrequently end in conundrums. If we speak of +a case of adaptation as a condition, a fact, we easily run the risk +of getting into confusion about cause and effect. For example: Is the +stag swift because he has long and slender legs, or are his legs long +because he is swift? In reality, swiftness and length of legs are cause +and effect in one. His legs have been so modified as to make him swift, +because he has put them continuously to whatever was his full speed, +which in his thick-footed ancestors was probably a very slow one. The +above question reads, therefore, more sensibly as follows: Has the stag +become swift because his legs have become long and slender, or have his +legs become long and slender because he has attained swiftness? Now, we +see that both halves of the double question are practically the same +and instantly suggest the answer. + +A fundamental difference between artificial machines and living +organisms is that the former are worn out by use, while the latter not +only repair the loss caused by use, but are also stimulated to further +increase. On the other hand, organs which are not put into function, +or are not used, _degenerate_. The various cells of the organ react +upon external stimuli by increased activity. Why this should be so is +another question--perhaps because those which do not would soon be not +fit to survive. Each cell has a function; the more specialized the more +intense it is. Every external stimulus, every contact with the outer +surroundings, is an insult, necessarily of detrimental effect, as it +disturbs the equilibrium of the cell body. It must, therefore, be of +advantage to the cells' well-being to return as soon as possible to the +_status quo ante_, and this can only be done by increased activity. + +In the present state of our knowledge, we can approach only the +simplest cases of acquisition of characteristics. Mostly they are +so complicated, subject to so many unthought-of conditions, that we +do not know from which end to approach the problem. Frequently the +supposed use of certain obvious features is the merest guesswork. This +applies especially to features to which we are not accustomed (although +wrongly so) to assign a function--for example, coloration. A green +tree-frog will with predilection rest on green leaves. The advantages +of concealment are obvious, and in this case he 'adapts himself' to the +surroundings by making for green localities: if he did not he would +be eaten up sooner than his more circumspect comrades. But this making +for, and sitting in, the green has not _necessarily_ made him of that +colour. Extreme advocates of one view would argue as follows: Once upon +a time there were among the offspring of ancestral tree-frogs some +which, among other colours, exhibited green, not much, perhaps not even +perceptible to our eyes. The occurrence of this colour, according to +them, was spontaneous, a freak--as if in reality there were anything +spontaneous in the sense of being causeless. The descendants of these +more greenish creatures, provided they did not pair with frogs of the +ordinary set, became still greener (by accumulative inheritance), and +so on, until the green was pronounced sufficient to be of advantage +when competition could set in. + +With this view there is always the difficulty of understanding how the +initial very small changes can be useful, unless we have to deal with +extremely simple organisms. Is it likely in the case of our frogs that +an almost imperceptible variation in colour makes them more fit to +live? We have to assume that 'luck' or chance kept them for generations +out of harm's reach, until the accumulation of green, hitherto quite +ineffective, neither harmful nor useful, became strong enough to be +effective. Such cases undoubtedly happen. + +But we can also argue out this problem in a somewhat different way, +which goes nearer to the root of the whole process. The original +slight, imperceptible change in pigmentation is not a spontaneous +freak; it was caused by the direct influence of the surroundings in +which the particular frogs happened to live, be this factor light or +temperature or food. Thus it stands to reason that the offspring, +living under similar conditions, will be acted upon in the same way. +That factor which has added green to the parents will add green to the +children, until by accumulative inheritance a more decidedly green +race is produced. + +The offspring of green plants do not become green when grown in the +dark; the young plants inherit not the green, but the capacity of +becoming green when acted upon by sunlight. This as an instance of +direct influence of the surroundings on a substance (chlorophyll), +which has not yet performed a function. But the kittens of a pair of +black cats produce black hair before they are born, and we have no +reason to doubt that the black pigment in their tegumentary structures +is ultimately referable to the action of the sunlight. In many +instances creatures living for generations in darkness become white, +pigmentless, and they regain it when exposed to light. For example, the +white, colourless Proteus from the caves of Adelsberg becomes clouded +grey, and ultimately jet black, when kept in a tank whence light is not +strictly excluded. + +Blindness is a very general characteristic of creatures which dwell in +darkness. There are all stages between total blindness and weak eyes. +Now, do these blind creatures live in darkness because they are blind, +or have they become first weak-eyed and then blind because of the +continuous disuse of their eyes? The former explanation has actually +been suggested! Individuals not smitten, but spontaneously, as a freak, +born with sore eyes, have crept into the darkness for relief and have +produced a blind race! To carry such a notion to the bitter end leads +to absurdities. Anyhow, it is not understandable where the benefit +of losing the eyesight arises. It can be explained only by continued +disuse: witness _Spalax typhlus_, the blind mole, and, above all, the +Endoparasites. + +Let us now take an example to explain the influence of a tangible +external stimulus. Repeated pressure produces callosities. Although +they are not exactly beneficial in the shape of corns on our toes, +they are so on our hands. At any rate, the morphologist can trace the +development of the footpads, nails, hoofs, and horns, step by step from +small beginnings. The cells of the Malpighian stratum, of the inner, +active portion of our epidermis, are excited to extra activity, and +by continually producing more horn cells than peel off the surface of +the skin in the normal process of wear and tear cause the formation +of the pad. It need scarcely be mentioned that hypertrophic growths +are not necessarily useful; they are often harmful, and in that case +pathological. + +Lastly, a few words about the very difficult question of _teleology_. +In trying to explain Evolution in a mechanical--sometimes called +monistic, but in reality natural--way, we exclude anything like a +set purpose, a goal, or ideal, a final condition which the organism +strives to attain. Unknown, however, to many morphologists, especially +embryologists, their writings are full of this teleological notion. +Indeed, there are many cases in which an organism becomes changed, and +quickly, too, in a way which cannot but be called reasonable. It starts +modifications, be they outgrowths, alterations in shape or colour, or +the making good of injuries received, which by 'short-cuts' produce +the only advantageous result that can reasonably satisfy the new +requirement or altered circumstances. + +Trees growing in precarious positions, after part of the supporting +rock has slipped away, throw out new roots, and rearrange some of +the old ones in the only way which could save the tree. In animals +which have lost part of a limb the wound closes up, and what is left +is turned into a serviceable stump--for example, in water-tortoises +(creatures in which reproduction of lost limbs does not happen). In +frogs and newts the lost part is reproduced, not correctly, but in a +good semblance. Tortoises which have had their shell smashed can throw +off an astonishingly large portion and renew the bone as well as the +overlapping scutes; but this mending is not neatly done. It serves the +requirement, but it is patchwork; the new shell is such as no tortoise +ever possessed before. + +Mammals transported into colder countries, or subjected to continued +exposure, grow a thicker coat; and the same kind of tree which in a +sheltered valley is tall, large-leaved, and soft-wooded, assumes a very +different aspect, although perhaps growing into a healthy specimen, +when planted on a wind-exposed hill. + +There is no room, or, rather, no time, to apply to these cases the +principle of many variations or the long-continued accumulation of +infinitely small changes. The thing is to be done quickly, or not +at all. Nor can we explain the mending of a wound, which implies an +activity of countless cells, simply as a case of, or similar to, the +reproduction of a lost part; against such an explanation militates the +almost absolute unlikelihood of that precise injury having happened +before to any of the creature's ancestors. + +Still, I think we are brought near the solution of the mystery by +such considerations. We see no difficulty in the regeneration of a +few cells, or in the making good of the disturbance suffered by one +of the most simple organisms; but we become suspicious when we see +that countless cells, not of one kind, but of the most varied tissues +and parts of the body, make common cause in remedying a defect in a +serviceable way. + +We must assume that since the beginning of life organisms have been +subjected to countless insults. We can scarcely speak of a wound in +an Amæba; but these insults have always been made good, and whenever +this was not the case, that particular organism came to an end. As +these organisms developed into more complicated ones, the possible +insults became more serious, more complicated; and the organisms took +adaptive measures so as to be superior to them. This action, I have +no hesitation in declaring, became by heredity a habit. The whole +creature became so thoroughly 'imbued' (for want of a better word) with +the finding of ways and means for meeting sudden, serious conditions, +that it now acts directly, and produces by a short-cut, with the least +amount of time and with the smallest possible waste of material, that +which meets the occasion, thereby saving the life of the individual +and that of the race. This we cannot but call reasonable and to the +purpose, although it is all carried out by _causæ efficientes_ without +there being any _causæ finales_. + + + + + GEOLOGICAL TIME AND EVOLUTION. + + +One million years is a stretch of time beyond our conception. We can +arrive at a more or less adequate understanding of what a million +individuals or concrete things means. Several Continental nations +can put more than a million men into the field. We can gaze at a +building which contains as many bricks; and we know that our own body +is composed of millions of millions of cells. No such help applies to +time, because that itself is an entirely relative, abstract conception. +We can imagine what one hundred years are like--a span of time +seemingly short to the hale and hearty octogenarian, enormous to the +child, totally inapplicable to certain animals whose whole life is +crowded into one single day. + +Astronomers have long ceased to reckon distances by miles or any +other understandable unit. They express the distances between us and +the stars and nebulæ by 'years of light.' Try to imagine a unit of +length equal to that which is passed through by light (186,000 miles +per second) in one year. Not so very long ago the enormous distances +resulting from astronomical calculations were looked upon as the most +serious objection to the correctness of the astronomers' views as to +the distances which separate our globe from the nearest fixed stars. +We have not yet accustomed ourselves to reckoning time by some similar +broadly-conceived standard--say æons of so many thousand years each. + +Unfortunately, we possess no data whatever for calculating the age +of the successive geological strata. Thanks to Lyell, the theory of +violent universal cataclysms has been done away with. It is more +probable that the same agencies have acted which are now changing +the aspect of the globe; and these changes are slow, as far as we +know them--at least, as far as the formation of sedimentary strata is +concerned, and these alone we have to deal with. Various calculations +have been made, based upon the denudation of the mountains, the +filling up of the valleys by the débris, the formation of deltas, +etc. The results give enormous stretches of time, but all of them +unsatisfactory, because the methods are so very local in their +application. + +The least objectionable attempt is that which, based upon astronomical +calculations, tried to fix the height of the last Glacial epoch[26] at +about 200,000 years ago, and asserted that since its beginning in the +Pliocene epoch as many as 270,000 years have elapsed. The duration +of the whole Tertiary period has by the same authorities been fixed +approximately at 3,000,000 to 4,000,000 years. Beyond this we cannot +venture without the wildest speculation; but we know to a certain +extent the thickness of the various sedimentary strata, which amount +in all to from 100,000 to 175,000 feet--on the average perhaps 130,000 +feet, or about twenty miles. + + [26] James Croll: 'On Geological Time, and the Probable Date of the + Glacial and Upper Miocene Period,' _Philos. Magazine_, xxxv., 1868, pp. + 363-384; xxxvi., pp. 141-154; 362-386. + +Unless we prefer giving up all attempt at calculation as absolutely +hopeless, and thus resign the whole problem, we must at least try to +arrive at some results, and then see if these cannot reasonably be made +use of. + +Neither geologist nor physicist, and no zoologist, would accept the +suggestion that these 130,000 feet of stratified rocks have been +deposited within only as many years, although the average rate of +deposit would in that case be not more than 1 foot per year. On the +other hand, an indignant protest is raised against the assumption of +1,000,000,000 years. + +Lord Kelvin[27] has come to the conclusion (from data which various +other authorities regard as very unsatisfactory) that not much more +than 100,000,000 years can have elapsed since the molten globe acquired +a consolidated crust. Further time must have passed before the surface +had become stable and cool enough to allow the temperature of the +collecting oceans to fall below boiling-point, and it is obvious that +life cannot possibly have begun until after this had happened. + + [27] William Thomson: 'On the Secular Cooling of the Earth,' _Transact. + R. S. Edinb._, xxiii., 1864, pp. 157-169. + +Wallace, in his 'Island Life,' by making use of Professor A. Geikie's +results as to the rate of denudation of matter by rivers from the +area of their basins, and estimating the average rate of deposition, +concludes that 'the time required to produce this thickness of rock +[Professor Haughton's maximum of 177,000 feet] at the present rate +of denudation and deposition is only 28,000,000 years.' Our lower +assumption of 130,000 feet thickness would give only 20,000,000 +years--a rate of 1 foot in 154 years. + +Again, if we prefer round numbers to start with, we have only to +assume that the age of the whole Tertiary period, with its 3,000 feet +thickness, is 3,000,000 years (_i.e._, 1,000 feet in 1,000,000 years, +or 1 foot in 1,000 years, surely an excessively slow rate); then +130,000,000 years would bring us to the bottom of the Laurentian or +pre-Cambrian deposits. Of course, it is a pure assumption that the +same rate of destruction and sedimentation applies to the whole of the +strata; but we know nothing to the contrary, especially if we consider +the average periods, the quick periods of extra activity, taken with +the slow periods or those of standstill. + +Dana estimated the length of the whole Tertiary period at one-fifteenth +of the Mesozoic and Palæozoic combined. If we take the duration of the +Tertiary period, as before, as 3,000,000 to 4,000,000 years, the total +will amount to from 45,000,000 to 60,000,000 years. + +Lastly, Walcott[28] has estimated the duration of the Palæozoic, +Mesozoic, and Cænozoic or Tertiary epochs at about 17,000,000, +7,000,000 and 3,000,000 years respectively, giving 27,700,000 years +from the beginning of the Cambrian; and Williams[29] has calculated the +relative duration of the smaller epochs. See the table on p. 149. + +The results of all these calculations fall surprisingly well within +the limits of Lord Kelvin's allowance. Of course they are based upon +assumptions, but none of them is inherently unreasonable; and it +was my purpose to draw attention to the surprising coincidence in +the closeness of these results, perhaps too good to be true. Such +calculations are considered close enough if they range within a few +multiples of each other. + + [28] 'Geological Time as indicated by the Sedimentary Rocks of North + America.' _Proc. Amer. Assoc. Adv. Sci._, xlii., 1893, pp. 129-169. + + [29] Henry Shaler Williams, 'Geological Biology.' New York, 1895. + +Zoologists have fallen into the habit of requiring enormous lengths of +time for the evolution of the animal kingdom. We know that Evolution is +at best a slow process, and the conception of the changes necessary to +evolve man from monkey-like creatures, these from the lowest imaginary +mammals, these from some reptilian stock, thence descending to Dipnoan +fish-like creatures, and so on back into Invertebrata, down to the +simple Monera--this conception is indeed gigantic. Innumerable, almost +endless, slow changes require seemingly unlimited time, and as time is +endless, why not draw upon it _ad libitum_? + +Huxley pointed out that it took nearly the whole of the Tertiary epoch +to produce the horse out of the four-toed Eohippos, and that, if we +apply this rate to the rest of its pedigree, enormous times would +be required. This is, however, a very misleading statement, which +necessitates considerable reduction, in conformity with our increased +palæontological knowledge. Animals of the genus Equus--namely, +Ungulata, with one toe, and with a certain tooth pattern--from the +Upper Miocene of India are now known. Moreover, it is not simply a +question of the gradual loss of the side-toes. The change from the +fox-sized little Eohippos and Hyracotherium, so far as skull, teeth, +vertebral column, and limbs are concerned (about the soft parts we know +next to nothing), is a very great one indeed. + +Elephants and mammoths seem to have developed very rapidly. None are +known from Eocene strata; but towards the end of the Miocene they had +spread over Asia, Europe, and North America, and that in great numbers. +The Eocene Amblypoda are still so different that we hesitate to connect +them ancestrally with the elephants. + +The Pinnipedia (seals and walruses) are strongly modified fissiped +Carnivora, and have existed since at least the Upper Miocene; the +transformation must have been accomplished within the Miocene period. + +We cannot shut our eyes to the fact that various groups have from the +time of their first appearance burst out into an exuberant growth of +modifications in form, size, and numbers, into all possible--and one +might almost say impossible--shapes; and they have done this within +comparatively short periods, after which they have died out not less +rapidly. It seems almost as if these go-ahead creatures had, by +accepting every possible modification and carrying the same to the +extreme, too quickly exhausted their plasticity--which, after all, +must have limits--thereby becoming unable to meet successfully the +requirements of further changes in their surroundings. The slowly +developing groups, keeping within main lines of Evolution, and not +being tempted into aberrant side-issues, had, after all, a much better +chance of onward evolution. + +A good example of the former are the Dinosaurs. We do not know +their ancestors; but we have here to deal only with their range of +transformation. The oldest known forms occur in the Upper Trias; they +attain their most stupendous development in the Upper Jurassic and in +the Wealden; and they have died out with the Cretaceous epoch. But +already some of their earliest forms had assumed bipedal gait, and the +Oolitic Compsognathus had developed almost bird-like hind-limbs. + +On the other hand, there are many instances of extremely slow +development--facts which raise the difficult question of 'persistent +types.' Are these due to a state of perfection which cannot be improved +upon? Or are they due to a kind of morphological consolidation (not +necessarily specialization) which can no longer yield easily, so that +therefore through changes in their surroundings they may come to an end +sooner than more plastic groups? + +Struthio, the ostrich; Orycteropus, the Cape ant-eater; Tapirus, and +many others, existed in the Miocene age practically as they are +now; but pre-Pliocene dolphins, cats, monkeys, stags, all belong to +closely-allied and well-defined 'genera,' but different from the living +forms. + +Alligators and crocodiles are known from the Upper Chalk; Tomistoma +since the Miocene; Gavialis since the Pliocene. + +The oldest surviving reptile is Sphenodon, the Hatteria of New Zealand, +a fair representative of what generalized reptiles of the later +Triassic period seem to have been like; and to the same period belongs +Ceratodus, the Australian mud-fish, hitherto the oldest known surviving +genus of a very ancient and low type so far as Vertebrata are concerned. + +Now let us see if the above estimates of geological time are so utterly +inapplicable to animal evolution. On purpose we take one of the lowest +estimates, about 28,000,000 years, and apportion them equally to the +various strata or epochs. + +The original owner of the famous Trinil skull, a _Pithecanthropus +erectus_, lived, according to some, in the Late Pliocene, according +to others in the Early Plistocene, period--that is to say, somewhere +about the beginning of our last Glacial epoch, some 270,000 years ago. +Assuming that he and his like reached puberty at sixteen to twenty +years of age, about 17,000 generations would lie between him and +ourselves, or, to put it more forcibly, between him and the lowest +living human races--say the Ceylonese Veddahs. Only 250 generations, +at twenty years, carry us back to 3000 B.C. (_i.e._, beyond +the ken of history); and if it be objected that the differences between +the oldest inhabitants of Egypt, the Naquada, and the present Fellahin +are very slight, we are welcome to multiply these differences sixty +or seventy fold, in order to arrive at the Pithecanthropus level. +But these Naquada had no metal implements, and there cannot be the +slightest doubt that the development of the human race went on by leaps +and bounds after certain discoveries had been made--to wit, the use +of implements and that of fire. That creature which first took up a +stone or a branch and wielded it thereby got such an enormous advantage +over his fellow-creatures that his mental and bodily development went +on apace. The same applies to the improvement of speech. We assume the +single, monophyletic origin of mankind at one place, in one district; +and the differences between some of the races of man are great enough +to constitute what we might call species. Compare the Venus of Milo, +that noble expression of the ancient Greeks' notion of female beauty, +with the 'products of art' of the Veddahs or the dwarfs of Central +Africa, or think of the beau-idéal which a Michael Angelo could +possibly have evolved if he had never seen any but such people. + + _TIME AND EVOLUTION_ + + ====================================================================== + I. |II.| III. | IV. | V. |VI.| VII. + | | | | | |Generations. + -----------+---+-----------+----------+--------------+---+------------ + |} |} |} |Adam and Eve | | 250 + Recent |} 5|} |} |Man, contem- | | 3,500 + Plistocene |} |} |} 270,000| porary with | | + | |} |} | Reindeer | | + | |} |} | in France | | + Pliocene -|} |} 3,000,000| |_Pithecanthro-| 16| 17,000 + |} |} |} 600,000| pus erectus_| | + Miocene -|}10|} |} |Anthropoid | 10| 60,000 + |} |} |}2,100,000| Apes | | + Eocene -|} |} |} |Lemures | 5| 420,000 + | | | | | | + Cretaceous | 10|} | 3,600,000| | | + Jurassic - | 5|} | 1,800,000| | | + Rhætic -|} |} |} |Prototheria, | 3| 1,800,000 + |} |} |} | or first | | + |} |} 7,200,000|} | Mammalia | | + Keuper -|} |} |}1,800,000| | | + Muschel- |} 5|} |} | | | + kalk |} |} |} | | | + New Red |} |} |} |Theromorpha | 4| 425,000 + Sandstone| | | | | | + Magnesian |} |} |} | | | + Limestone|} |} |} | | | + Lower Red |} |} |} |Proreptilia | 4| 250,000 + Sandstone|} |} |}4,000,000| | | + Coal- |}15|} |} |Eotetrapoda | 4| 500,000 + measures |} |} |} | | | + Mountain |} |}17,500,000|} | | | + Limestone | |} | | | | + Devonian -| 15|} | 4,000,000|Dipnoi and | 5| 1,000,000 + | |} | |Crossopterygii| | + Silurian -| 10|} | 2,700,000|First fishlike| 3| 900,000 + | |} | | creatures | | + Ordovician | 10|} | 2,700,000| | | + Cambrian -| 15|} | 4,000,000| Sum total of| | + Laurentian | | | | generations| | --------- + Archæan | | | | (about) | | 5,375,000 + or Meta- | | | | | | + morphic | | | | | | + ====================================================================== + +EXPLANATION OF THE TABLE ON P. 149. + + Column I. contains the names of the successive sedimentary strata. + + " II. contains the percentage of the duration of the various epochs, + according to _Williams_, the time from the Cambrian until recent times + being taken as 100. + + " III. gives the estimated duration in years of the Palæozoic, + Mesozoic, and Cænozoic periods, according to _Walcott_. + + " IV. gives in years the duration of the various smaller epochs, as + computed from Walcott and Williams' statements. + + " V. Representatives of stages of the ancestral line of man. The + names stand in the level of the stratum in which they have made their + first appearance. + + " VI. contains the number of years which, in the present + calculation, have been assumed necessary for the animal to reach + puberty. + + " VII. contains the number of generations which can have elapsed + from stage to stage. For example, 60,000 generations separate the + earliest known anthropoid apes from Pithecanthropus. + +Let us follow the descent of man further back. The next stage, +reckoning backwards, is that from Pithecanthropus to _bonâ-fide_ +anthropoid apes. They are represented in the Miocene by various +genera--_e.g._, Pliopithecus and Dryopithecus. According to Croll and +Wallace, 850,000 years ago carry us into the Miocene epoch. Assuming +that these apes lived about 600,000 years before Pithecanthropus, +namely, in the later half of the Miocene, and taking puberty at ten +years of age, a high estimate, we get not less than 60,000 generations. + +2. From Apes back to lowest Lemurs in the lowest Eocene. The date of +Eocene being fixed at 3,000,000, we have about 2,100,000 years for this +stage; assuming as much as five years for puberty, this results in +420,000 generations. + +3. From Lemures to Prototheria. The earliest known mammalian remains +come from the Rhætic, or top formation of the Triassic epoch; allowing +for the Rhætic only 100,000 years, we have to add the whole of the +Jurassic and Cretaceous, in all about 5,500,000 years. Assuming three +years for a generation, we get 1,800,000 generations. + +4. From Prototheria to something like the Theromorpha at the bottom of +the Triassic strata. A duration of 1,700,000 years divided by four +gives 425,000 generations. + +5. From Theromorpha to Proreptilia, represented by Eryops and Cricotus +from the Lower Permian of Texas. Allowing 1,000,000 years, each +generation at four years, we obtain 250,000 generations. + +6. From Proreptilia to Eotetrapoda, the first terrestrial Vertebrata, +represented by something like the Stegocephali, the earliest of which +are known from the Coal-measures. Assuming them to have come into +existence at the bottom of the Coal-measures, for the duration of which +we may guess 2,000,000 years, we get, with four years' allowance for +puberty, 500,000 generations. + +7. From Eotetrapoda to a not yet separated or differentiated group +of Crossopterygian and Dipnoan fishes, both of which are known from +Devonian strata. The duration of the latter has been computed at +4,000,000 years, which, with 1,000,000 for the Mountain Limestone +formation, gives us 5,000,000 for this stage. Assuming, for the sake +of round numbers, as much as five years for a generation, we get +1,000,000 generations. + +8. Earliest stage, down to the first fish-like creatures. Teeth and +spines indicating the existence of fishes are known from the Upper +Silurian. By carrying the earliest fishes down to the bottom of the +Silurian, with 2,700,000 years' duration, and allowing three years for +attaining puberty, the calculation results in 900,000 generations. + +Further back we cannot go. We do not know of any Vertebrate remains +from the Ordovician and Cambrian, which together represent 6,700,000 +years, enough for at least half as many generations of Prochordate +creatures. The pre-Cambrian or Laurentian epoch lies quite beyond the +reach of calculation, nor have we any trustworthy fossil remains of +living matter from these strata, to which, however, Haeckel and others +refer the first beginnings of life. + +All the above calculations are, of course, only approximate. What we +do know is the existence of representatives of the stages, our proofs +being the fossils; but when we refer the origin of the Eotetrapoda, +for example, to the bottom and not somewhere to the middle of the +Coal-measures, we are guessing merely. Alterations in the levels +assumed for the various stage-representatives will, of course, alter +the result of the number of generations; but the leading idea, as +a whole, is not thereby upset. The fact remains that in the Upper +Silurian we have fishes; from the Coal-measures onwards, fishes and +Amphibia; since the Permian, fishes, Amphibia, and reptiles; since the +end of the Trias these three classes and the Mammalia; and lastly, at +least since the Plistocene, man himself. If Evolution is true at all, +the transformation from early fish-like creatures to man has come about +within these epochs. Being able to assign a time of duration to each +of them, with an approximate total of 21,000,000 years, we are also +able to put the whole ancestral series to a test by expressing each +great stage in generations. The result is very satisfactory. The whole +enormous stretch from the lowest fish-like creatures to man has been +resolved into more than 5,000,000 successive generations, and each of +these means a little step forwards in onward Evolution. + +Nothing is to be gained for the understanding of our problem of +Evolution if we multiply this enormous number of generations by ten +or any other multiple. We are not able to conceive changes so small +as those which necessarily have existed between Pithecanthropus and +man if the whole striking difference is analysed into 17,000 steps. +Every one of these stages in the modifications of the muscles, the +skeletal framework, increase of brain, shortening of the trunk, +lengthening of the legs, improvement of the hands, loss of the hairy +coat, etc., is truly microscopical, imperceptible, just as the +Evolutionist imagines the whole process to have been. Again, where is +the difficulty implied by the change from an air-breathing, in many +structural points half-amphibian, fish into a primitive land-crawling +four-footed creature, if we are allowed to resolve the transformation +into 1,000,000 stages? So far from there being any difficulty, rather +does it appear questionable if so many infinitely small changes have +been necessary to bring about this result. + +One thousand years make apparently no difference in the evolution of +animals, nor does one second change the aspect of the hands on the +face of a clock, nor did Julius Cæsar's commission of scientific men +appreciate the error of about eleven minutes in the length of the year +beyond its real value; but now the Russians are, owing to this neglect, +nearly two weeks behind the civilized nations. + + + THE END. + + + BILLING AND SONS, PRINTERS, GUILDFORD. + + + By PROFESSOR ERNST HAECKEL + + + MONISM; + OR, + The Confession of Faith of a Man of Science. + + Translated from the German by J. D. F. GILCHRIST. + + _Crown 8vo., cloth. Price 1s. 6d. net._ + +'We may readily admit that Professor Haeckel has stated his case with +the clearness and courage which we should expect of him, and that +his lecture may be regarded as a fair and authoritative statement +of the views now held by a large number of scientifically educated +people.'--_Times._ + +'The Monism, which is the substance of his faith, is thus defined by +him: "Our conviction that there lives one spirit in all things, and +that the whole cognizable world is constituted, and has been developed, +in accordance with one common fundamental law." As the confession +of a distinguished man of science, this little work deserves to be +read.'--_North British Daily Mail._ + +'This "Confession of Faith" was delivered by the great German +scientist, its author, as an extemporaneous address at Altenburg +rather more than two years ago. There are, no doubt, a large number of +English readers who will welcome a translation, for this "connecting of +religion and science" has long troubled many earnest students of modern +science.'--_Publisher's Circular._ + +'This is a little book of great daring, an example of the wild +speculative flights of one of the very ablest and greatest of our +contemporary men of science.'--_Aberdeen Free Press._ + +'The address, whatever we may think of its conclusions, is, however, +most interesting reading, and is admirably done into English by the +translator.'--_Literary World._ + + + LONDON: ADAM & CHARLES BLACK, SOHO SQUARE. + + + _Demy 8vo., price 7s. 6d. net._ + + SOURCES OF THE APOSTOLIC + CANONS. + + _With a Treatise on the Origin of the Readership and other Lower Orders._ + + By Professor ADOLF HARNACK. + + Translated by LEONARD A. WHEATLEY. + + _With an Introductory Essay on the Organization of the Early Church + and the Evolution of the Reader._ + + By the Rev. JOHN OWEN, Author of 'Evenings with the Skeptics.' + +'Dr. Adolf Harnack is at the present time undoubtedly the leading +liberal authority in Germany on matters connected with early Christian +history.'--_The Times._ + +'Those who are interested in early Church history know how to prize +anything from the pen of Prof. Harnack. They will not be disappointed +with the present paper, in which, with his accustomed learning and +acute criticism, he annotates and comments upon the fragments of +primitive church law which partly form the basis of the Apostolic +Canons.'--_British Weekly._ + +'The wide circulation of this volume would be of the happiest augury +for a more scientific and worthy conception of the organization of the +primitive Church.'--Dr. MARCUS DODS in _The Bookman_. + + + + _Crown 8vo., cloth, price 1s. 6d. net._ + + CHRISTIANITY AND HISTORY. + + By ADOLF HARNACK. + + Translated, with the Author's sanction, by THOMAS BAILEY + SAUNDERS, with an Introductory Note. + +'It is highly interesting and full of thought. The short introductory +note with which Mr. Saunders prefaces it is valuable for its +information and excellent in its tone.'--_Athenæum._ + +'A singularly able exposition and defence of Christianity, as seen in +the newer light, by one of the most learned and acute "evangelical" +critics of Germany. The essay is a masterly one.'--_Glasgow Herald._ + +' ... We hope the lecture will be widely read.'--_Primitive Methodist +Quarterly Review._ + +'The lecture itself is weighty in its every word, and should be read +and re-read by those desiring to have in a nutshell the central +positions of modern Christianity.'--_Christian World._ + + + LONDON: ADAM & CHARLES BLACK, SOHO SQUARE. + + + _Third Edition. Crown 8vo., cloth, price 5s._ + + SKETCH OF THE HISTORY OF + ISRAEL AND JUDAH. + + By J. WELLHAUSEN, + PROFESSOR AT MARBURG. + +'This work is now issued for the third time as an independent treatise. +It admirably epitomizes the subject, and exhibits on almost every page +evidences of Professor Wellhausen's profound study.'--_Publishers' +Circular._ + +'We would only say that those who differ from his critical views will +yet do well to study them, and to read this history in which he applies +them. Its separate publication, in a handy form and at a moderate +price, makes it generally accessible.'--_North British Daily Mail._ + +'The publication in a separate form of Professor Wellhausen's article +in the "Encyclopædia Britannica" on "Israel" will be very warmly +welcomed by many readers.'--_Manchester Guardian._ + +'We are very glad to welcome an edition of Professor Wellhausen's +"Sketch of the History of Israel and Judah" in a convenient and handy +form. This is the first time it has appeared in a separate form. It is +already known to students; it ought now to become popular. It is based +on the learned author's studies in Hebrew literature and history, and, +though not controversial in form, it differs totally from orthodox +presentations of the subject.'--_Westminster Review._ + +'A sketch which has created such widespread and profound interest as +this could not be kept in the pages of a voluminous encyclopædia. +Wellhausen's words necessarily have exceptional importance, even in +the esteem of those who differ from him _toto coelo_.'--_Baptist +Magazine._ + +'The profound scholarship of the author does not elevate his writing +above the interest of the general reader, and a vivid idea of the +involved Jewish history is obtainable from this volume.'--_Christian +Advocate._ + + + LONDON: ADAM & CHARLES BLACK, SOHO SQUARE. + + + _Demy 8vo., boards, price 3s. 6d. net._ + + A CLASSIFICATION OF + VERTEBRATA, + RECENT AND EXTINCT. + + With Diagnoses and Definitions, a Chapter on Geographical + Distribution, and an Etymological Index. + + By HANS GADOW, M.A., PH.D., F.R.S., + + STRICKLAND CURATOR AND LECTURER ON ZOOLOGY TO THE UNIVERSITY, + CAMBRIDGE. + +'At the end of his work Dr. Gadow adds a useful chapter on the +geographical distribution of the Vertebrata, with a table showing +the approximate number of the known recent species. He also gives +a fanciful though striking calculation to show how some groups are +still in the ascendant, while others are distinctly declining. The +little volume is indeed a welcome addition to the biological student's +library, and it deserves the wide circulation which its author's +eminence is likely to ensure for it.'--_Natural Science._ + +'It is a book, it need hardly be said, for the student; it is simply +a list of the principal sub-divisions of backboned animals, with just +as much definition as is needed. It may be regarded as an exceedingly +concentrated extract of a full text-book of the vertebrates.'--_Daily +Chronicle._ + + + + _Demy 8vo., cloth, price 21s._ + + IN NORTHERN SPAIN. + + By Dr. HANS GADOW, M.A., PH.D., F.R.S. + + _Containing Map and 89 Illustrations._ + +'Some years back "Wild Spain," one of the best books of its kind, +made you desirous of knowing more of the country. And Hans Gadow has +deepened this feeling in his excellent volume "In Northern Spain," +and that to an enormous extent. Dwelling at inn or farm, or in their +own tent, they saw the country as it has been seen but rarely, and +they came to know the inhabitants as they can be known in no other +fashion.'--_Black and White._ + +'To persons visiting the provinces with which the author deals, this +book will be invaluable, and will do more to point their attention to +objects of interest than existing guide-books of Spain, most of which +are out of date.'--_The Field._ + +'About the best book of European travel that has appeared these many +years.'--_Literary World._ + + + LONDON: ADAM & CHARLES BLACK, SOHO SQUARE. + + +Transcriber's Notes + + Variations in spelling, punctuation and hyphenation have been retained + except in obvious cases of typographical errors. + Inconsistent hyphenation and spelling are as in the oringinal. + Italics are shown thus _italic_ and underline thus *underline*. + + + + + +End of the Project Gutenberg EBook of The Last Link, by Ernst Haeckel + +*** END OF THIS PROJECT GUTENBERG EBOOK THE LAST LINK *** + +***** This file should be named 44541-8.txt or 44541-8.zip ***** +This and all associated files of various formats will be found in: + http://www.gutenberg.org/4/4/5/4/44541/ + +Produced by Chris Curnow, Les Galloway and the Online +Distributed Proofreading Team at http://www.pgdp.net (This +file was produced from images generously made available +by The Internet Archive) + + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. 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You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: The Last Link + Our Present Knowledge of the Descent of Man + +Author: Ernst Haeckel + +Commentator: Hans Gadow + +Release Date: December 29, 2013 [EBook #44541] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK THE LAST LINK *** + + + + +Produced by Chris Curnow, Les Galloway and the Online +Distributed Proofreading Team at http://www.pgdp.net (This +file was produced from images generously made available +by The Internet Archive) + + + + + + +</pre> + + + +<h1>THE LAST LINK</h1> + +<p class="center">OUR PRESENT KNOWLEDGE OF THE + DESCENT OF MAN</p> + +<p class="center space-above"><small>BY</small><br /> +ERNST HAECKEL<br /> +<small>(JENA)</small></p> + +<p class="center space-above"><small>WITH NOTES AND BIOGRAPHICAL SKETCHES<br /> +BY</small><br /> +HANS GADOW, F.R.S.<br /> +<small>(CAMBRIDGE)</small></p> + + +<p class="center space-above">LONDON<br /> +ADAM AND CHARLES BLACK<br /> +1898</p> + +<hr class="chap"/> + +<h2>CONTENTS.</h2> + +<table id="toc" summary="contents"> +<tr> + <td> </td> + <td class="tdr"><span class="smcap">page</span></td> +</tr> +<tr> + <td class="tdl"><big>THE LAST LINK</big></td> + <td class="tdr"> </td> +</tr> +<tr> + <td class="tdl"> INTRODUCTORY</td> + <td class="tdr"><a href="#Page_1">1</a></td> +</tr> +<tr> + <td class="tdl"> COMPARATIVE ANATOMY</td> + <td class="tdr"><a href="#Page_8">8</a></td> +</tr> +<tr> + <td class="tdl"> PALÆONTOLOGY</td> + <td class="tdr"><a href="#Page_20">20</a></td> +</tr> +<tr> + <td class="tdl"> OTHER EVIDENCE</td> + <td class="tdr"><a href="#Page_42">42</a></td> +</tr> +<tr> + <td class="tdl"> STAGES RECAPITULATED</td> + <td class="tdr"><a href="#Page_47">47</a></td> +</tr> +<tr> + <td class="tdl"><big>BIOGRAPHICAL SKETCHES:</big></td> + <td class="tdr"> </td> +</tr> +<tr> + <td class="tdl"> LAMARCK, SAINT-HILAIRE, CUVIER, BAER,</td> + <td class="tdr"> </td> +</tr> +<tr> + <td class="tdl"> MUELLER, VIRCHOW, COPE, KOELLIKER, GEGENBAUR,</td> + <td class="tdr"> </td> +</tr> +<tr> + <td class="tdl"> HAECKEL</td> + <td class="tdr"><a href="#Page_80">80</a></td> +</tr> +<tr> + <td class="tdl">THEORY OF CELLS</td> + <td class="tdr"><a href="#Page_115">115</a></td> +</tr> +<tr> + <td class="tdl">FACTORS OF EVOLUTION</td> + <td class="tdr"><a href="#Page_117">117</a></td> +</tr> +<tr> + <td class="tdl">GEOLOGICAL TIME AND EVOLUTION</td> + <td class="tdr"><a href="#Page_135">135</a></td> +</tr> +</table> + +<hr class="chap" /> +<div class="chapter-beginning"/> + +<h2>NOTE</h2> + + +<p>The address I delivered on August 26 at the +Fourth International Congress of Zoology at +Cambridge, 'On our Present Knowledge of +the Descent of Man,' has, I find, from the +high significance of the theme and the +general importance of the questions connected +with it, excited much interest, and +has led to requests for its publication. +Hence this volume, edited by my friend +Dr. H. Gadow, my pupil in earlier days, +who has not only revised the text, but has +also enriched it by many valuable additions +and notes.</p> + +<p class="right">ERNST HAECKEL.</p> + +<p><small><i>Jena, December, 1898.</i></small></p> + +<p><span class="pagenum"><a name="Page_1" id="Page_1">[Pg 1]</a></span></p> + +<hr class="chap" /> +<div class="chapter-beginning"/> +<h2>THE LAST LINK</h2> + + +<p>At the end of the nineteenth century, the +age of 'natural science,' the department of +knowledge that has made most progress is +zoology. From zoology has arisen the study +of transformism, which now dominates the +whole of biology. Lamarck<a name="FNanchor_1_1" id="FNanchor_1_1"></a><a href="#Footnote_1_1" class="fnanchor">[1]</a> laid its foundation +in 1809, and forty years ago Charles +Darwin obtained for it a recognition which +is now universal. It is not my task to repeat +the well-known principles of Darwinism. I +am not concerned to explain the scientific +value of the whole theory of descent. The +whole of our biological study is pervaded by +it. No general problem in zoology and<span class="pagenum"><a name="Page_2" id="Page_2">[Pg 2]</a></span> +botany, in anatomy and physiology, can be +discussed without the question arising, How +has this problem originated? What are the +real causes of its development?</p> + +<p>This question was almost unknown seventy +years ago, when Charles Darwin, the great +reformer of biology, began his academical +career at Cambridge as a student of theology. +In the same year, 1828, Carl Ernst von +Baer<a name="FNanchor_2_2" id="FNanchor_2_2"></a><a href="#Footnote_2_2" class="fnanchor">[2]</a> published in Germany his classical +work on the embryology of animals, the first +successful attempt to elucidate by 'observation +and reflection' the mysterious origin +of the animal body from the egg, and to +explain in every respect the 'history of the +growing individuality.' Darwin at that time +had no knowledge of this great advance, and +he could not divine that forty years later +embryology would be one of the strongest +supports of his own life's work—of that very +theory of transformism which, founded by +Lamarck in the year of Darwin's birth,<span class="pagenum"><a name="Page_3" id="Page_3">[Pg 3]</a></span> +was accepted with enthusiasm by Charles's +grandfather Erasmus. There is no doubt +that of all the celebrated naturalists of the +nineteenth century Darwin achieved the +greatest success, and we should be justified +in designating the last forty years as the +Age of Darwin.</p> + +<p>In searching for the causes of this unexampled +success, we must clearly separate +three sets of considerations: first, the comprehensive +reform of Lamarck's transformism, +and its firm establishment by the many +arguments drawn from modern biology; +secondly, the construction of the new theory +of selection, as established by Darwin, and +independently by Alfred Wallace (a theory +called Darwinism in the proper sense); +thirdly, the deduction of anthropogeny, that +most important conclusion of the theory of +descent, the value of which far surpasses all +the other truths in evolution.</p> + +<p>It is the third point of Darwin's theory +that I shall discuss here; and I shall discuss<span class="pagenum"><a name="Page_4" id="Page_4">[Pg 4]</a></span> +it chiefly with the intention of examining +critically the evidence and the different +conclusions which at present represent our +scientific knowledge of the descent of man +and of the different stages of his animal +pedigree.</p> + +<p>It is now generally admitted that this +problem is the most important of all biological +questions. Huxley was right when +in 1863 he called it the question of questions +for mankind. The problem which underlies +all others, and is more deeply interesting than +any other, is as to the place which man +occupies in nature and his relations to the +universe of things. 'Whence our race has +come; what are the limits of our power over +nature, and of nature's power over us; to +what goal are we tending—these are the +problems which present themselves anew +and with undiminished interest to every man +born into the world.' This impressive view +was explained by Huxley thirty-five years ago +in his three celebrated essays on 'Evidence<span class="pagenum"><a name="Page_5" id="Page_5">[Pg 5]</a></span> +as to Man's Place in Nature.' The first is +entitled 'On the Natural History of the Man-like +Apes'; the second, 'On the Relations of +Man to the Lower Animals'; the third, 'On +some Fossil Remains of Man.' Darwin himself +felt the burden of these problems as much +as Huxley; but in his chief work, 'On the +Origin of Species,' in 1859, he had purposely +only just touched them, suggesting that the +theory of descent would shed light upon the +origin of man and his history. Twelve years +later, in his celebrated work on 'The Descent +of Man, and Selection in Relation to Sex,' +Darwin discussed fully and ingeniously all +the different sides of this 'question of +questions' from the morphological, historical, +physiological, and psychological points of +view. As early as 1866 I myself had applied +in the <i>Generelle Morphologie der Organismen</i> +the theory of transformism to anthropology, +and had shown that the fundamental law of +biogeny claims the same value for man as for +all the other animals. The intimate causal<span class="pagenum"><a name="Page_6" id="Page_6">[Pg 6]</a></span> +connection between ontogeny and phylogeny, +between the development of the individual and +the history of its ancestors, enables us to gain +a safe and certain knowledge of our ancestral +series. I had at that time distinguished in +this series ten chief degrees of vertebrate +organization. I attributed the highest importance +to the logical connection of anthropogeny +with transformism. If the latter be +true, the truth of the former is absolute. +'Our theory that man is descended from +lower vertebrates, and immediately from apes +or primates, is a case of special <i>deduction</i> +which follows with absolute certainty from the +general <i>induction</i> of the theory of descent.' +The full proof and detailed explanation of +this view was afterwards given in my +'History of Natural Creation,' and especially +in my 'Anthropogeny.'<a name="FNanchor_3_3" id="FNanchor_3_3"></a><a href="#Footnote_3_3" class="fnanchor">[3]</a> Lastly, it has +received an ample scientific and critical +foundation in the third part of my 'Systematic +Phylogeny.'<sup>[3]</sup></p> + +<p><span class="pagenum"><a name="Page_7" id="Page_7">[Pg 7]</a></span></p> +<p>During the forty years which have elapsed +since Darwin's first publication of his theories +an enormous literature, discussing the <i>general +problems</i> of transformism as well as its special +application to man, has been published. In +spite of the wide divergence of the different +views, all agree in one main point: the +natural development of man cannot be separated +from general transformism. There are +only two possibilities. Either all the various +species of animals and plants have been +created independently by supernatural forces +(and in this case the creation of man also is a +miracle); or the species have been produced +in a natural way by transmutation, by adaptation +and progressive heredity (and in this +case man also is descended from other vertebrates, +and immediately from a series of +primates). We are absolutely convinced that +only the latter theory is fully scientific. To +prove its truth, we have to examine critically +the strength of the different arguments claimed +for it.</p> + +<p><span class="pagenum"><a name="Page_8" id="Page_8">[Pg 8]</a></span></p> + +<hr class="chap"/> + +<h2>I.</h2> + + +<p>First, we have to consider the relative +place which comparative anatomy concedes +to man in the 'natural system' of animals, +for the true value of our 'natural classification' +is based upon its meaning as a pedigree. +All the minor and major groups of the system—the +classes, legions, orders, families, genera, +and species—are only different branches of +the same pedigree. For man himself, his +place in the pedigree has been fixed since +Lamarck,<a name="FNanchor_5_5" id="FNanchor_5_5"></a><a href="#Footnote_5_5" class="fnanchor">[5]</a> in 1801, defined the group of +vertebrates. The most perfect<a name="FNanchor_6_6" id="FNanchor_6_6"></a><a href="#Footnote_6_6" class="fnanchor">[6]</a> of these are<span class="pagenum"><a name="Page_9" id="Page_9">[Pg 9]</a></span> +the Mammalia; and at the head of this class +stands the order of Primates, in which Linnæus, +in 1735, united four 'genera'—Homo, +Simia, Lemur, and Vespertilio. If we exclude +the last-named, the Chiroptera of modern +zoology, there remain three natural groups of +Primates—the Lemures, the Simiæ, and the +Anthropi or Hominidæ. This is the classification<span class="pagenum"><a name="Page_10" id="Page_10">[Pg 10]</a></span> +of the majority of zoologists; but if we +compare man with the two chief groups of +monkeys—the Eastern monkeys (or Catarrhinæ) +and the Western or American monkeys +(Platyrrhinæ)—there can be no doubt that the +former group is much more closely related to +man than is the latter. In the natural order +of the Catarrhinæ we find united a long series +of lower and higher forms. The lowest, the +Cynopitheci, appear still closely related to +the Platyrrhinæ and to the Lemures; while, +on the other hand, the tailless apes (Anthropomorphæ) +approach man through their +higher organization. Hence one of our best +authorities on the Primates, Robert Hartmann,<a name="FNanchor_7_7" id="FNanchor_7_7"></a><a href="#Footnote_7_7" class="fnanchor">[7]</a> +proposed to subdivide the whole +order of the Simiæ into three groups:</p> + +<p>(1) Primarii, man together with the other +Anthropomorphæ, or tailless apes; (2) +Simiæ, all the other monkeys; (3) Prosimiæ, +or Lemurs. This arrangement has received<span class="pagenum"><a name="Page_11" id="Page_11">[Pg 11]</a></span> +strong support from the interesting discovery +by Selenka that the peculiar placentation of +the human embryo is the same as in the +great apes, and different from that of all the +other monkeys. Our choice between these +different classifications of Primates is best +determined by the important thesis of Huxley, +in which, in 1863, he carried out a most careful +and critical comparison of all the anatomical +gradations within this order. In my opinion, +this ingenious thesis—which I have called the +Huxleyan Law, or the 'Pithecometra-thesis +of Huxley'—is of the utmost value. It runs +as follows: 'Thus, whatever system of +organs be studied, the comparison of their +modifications in the ape-series leads to one +and the same result—that the structural +differences which separate man from the +gorilla and the chimpanzee are not so great +as those which separate the gorilla from the +lower apes.' If we accept the Huxleyan +law without prejudice, and apply it to the +natural classification of the Primates, we<span class="pagenum"><a name="Page_12" id="Page_12">[Pg 12]</a></span> +must concede that man's place is within the +order of the Simiæ. On examining this +relation with care, and judging with logical +persistence, we may even go a step further. +Instead of the wider conception of 'Simiæ,' +we must use the restricted term of Catarrhinæ, +and our Pithecometra-thesis has then +to be formulated as follows: <i>The comparative +anatomy of all organs of the group of Catarrhine +Simiæ leads to the result that the +morphological differences between man and +the great apes are not so great as are those +between the man-like apes and the lowest +Catarrhinæ</i>. In fact, it is very difficult to +show why man should not be classed with +the large apes in the same zoological family. +We all know a man from an ape; but it is +quite another thing to find differences which +are absolute and not of degree only. Speaking +generally, we may say that man alone +combines the four following features: (1) +Erect walk; (2) extremities differentiated +accordingly; (3) articulate speech; (4) higher<span class="pagenum"><a name="Page_13" id="Page_13">[Pg 13]</a></span> +reasoning power. Speech and reason are +obviously relative distinctions only—the direct +result of more brains and more brain-power, +the so-called mental faculties. The erect walk +is not an absolutely distinguishing characteristic: +the large apes likewise walk on their +feet only, supporting their bodies by touching +the ground with the backs of their hands—in +fact, with their knuckles—and this is a mode +of progression very different from that of the +tailed monkeys, which walk upon the palms +of their hands. There are, however, two +obvious differences in the development of +the muscles. In man alone the gastrocnemius +and the soleus muscle are thick +enough to form the calf of the leg, and +the glutæus maximus is enlarged into the +buttocks. A fourth glutæal muscle occurs +occasionally in man, while it is constantly +present in apes as the so-called musculus +scansorius. Concerning the muscles of the +whole body, we cannot do better than quote +Testut's summary: 'The mass of recorded<span class="pagenum"><a name="Page_14" id="Page_14">[Pg 14]</a></span> +observations upon the muscular anomalies in +man is so great, and the agreement of many +of these with the condition normal in apes is so +marked, that the gap which usually separates +the muscular system of man from that of the +apes appears to be completely bridged over.'</p> + +<p>There are, for example, the muscles of the +ear. In most people the majority, or even +all of them, are no longer movable at will, +while in the apes they are still in use. The +important point, however, is that these +muscles are still present in man, although +often in a reduced condition. They are the +following: (1) Musculus auricularis anterior +or attrahens auris, which is frequently much +reduced and no longer reaches the ear at all, +being then absolutely useless; (2) Musculus +auricularis superior or attollens auris, more +constant than the former; (3) Musculus +auricularis posterior or retrahens auris, likewise +often functional. Occasionally smaller +slips differentiated from these three muscles +are present, and as so-called intrinsic muscles<span class="pagenum"><a name="Page_15" id="Page_15">[Pg 15]</a><br /><a name="Page_16" id="Page_16">[Pg 16]</a></span> +are restricted to the ear itself; their function +is, or was, that of curling up or opening the +external ear.</p> + +<div class="figcenter"><a href="./images/i_0231.jpg"> + <img src="./images/i_0231.jpg" alt="Outlines of the Left Ear"></img></a> +</div> +<p class="center"><span class="smcap">Outlines of the Left Ear of—</span></p> + +<blockquote> +<p><small>1. <i>Lemur macaco</i>; 2. <i>Macacus rhesus</i>, the Rhesus monkey; +3. Cercopithecus, a macaque; 4. human embryo of six months; +5. man, with Darwin's point well retained: the dotted outline is that +of the ear of a baboon; 6. orang-utan (after G. Schwalbe):<a name="FNanchor_8_8" id="FNanchor_8_8"></a><a href="#Footnote_8_8" class="fnanchor">[8]</a> <sup>x</sup> the +original tip of the ear; 7. human ear with the principal muscles.</small></p> +</blockquote> + +<p>In connection with the ear, I may touch +upon another interesting and most suggestive +little feature which is present in many +individuals—namely, 'Darwin's point.' This +is the last remnant of the original tip of the +ear, before the outer, upper, and hinder rim +became doubled up or folded in. It is a +feature quite useless, and absolutely impossible +of interpretation, excepting as the vestige of +such previous ancestral conditions as are +normal in the monkeys.</p> + +<p>In some cases the reduction of muscles +has proceeded further in apes than in man—for +example, the muscles of the little toe. +Another instance is afforded by the coccyx or +vestige of the tail; this is still furnished with +muscles which are now in man, as well as in +the apes, quite useless, and vary considerably +with every sign of degeneration, most so in +the orang-utan.</p> + +<p><span class="pagenum"><a name="Page_17" id="Page_17">[Pg 17]</a></span></p> + +<p>Darwin has mentioned the frequent action +of the 'snarling muscle,' by which, in sneering, +our upper canine teeth are exposed, like those +of a dog prepared to fight.</p> + +<p>Monkeys and apes possess vocal sacs, +especially large in the orang-utan; survivals +of them, although no longer used, persist in +man in the shape of a pair of small diverticula, +the pouches of Morgagni, between the +true and the false vocal cords.</p> + +<p>'In the native Australians, the dental formula +appears least removed from the hypothetical +original type, for in it are still found +complete rows of splendid teeth, with powerfully-developed +canines and molars, the latter +being either uniform, or even increasing in +size, as we proceed backwards, in such a +way that the wisdom tooth is the largest of +the series. This is decidedly a pithecoid +characteristic which is always found in apes. +The upper incisors of the Malay, apart from +their prognathous disposition, have occasionally +a distinctly pithecoid form, their anterior<span class="pagenum"><a name="Page_18" id="Page_18">[Pg 18]</a></span> +surface being convex, and their lingual surface +slightly concave. The ancestors of +Europeans seem to have had the same form +of teeth, for the oldest existing fragments of +skulls from the Mammoth age (<i>e.g.</i>, the jaws +from La Naulette, in Belgium) reveal tooth-forms +which must be classed with those of +the lowest races of to-day.'<a name="FNanchor_9_9" id="FNanchor_9_9"></a><a href="#Footnote_9_9" class="fnanchor">[9]</a></p> + +<p>Now we are able to apply this fundamental +Pithecometra-thesis directly to the classification +of the Primates and to the phylogeny of +man, which is intimately connected with it, +because in this order, as in all the other +groups of animals, the natural system is the +clear expression of true phylogenetic affinity. +Four results follow from our thesis: (1) The +Primates, as the highest legion or order of +mammals, form one natural, monophyletic +group. All the Lemures, Simiæ, and +Homines descend from one common ancestral<span class="pagenum"><a name="Page_19" id="Page_19">[Pg 19]</a></span> +form, from a hypothetical 'Archiprimas.' +(2) The Lemures are the older and +lower of the natural groups of the Primates; +they stand between the oldest Placentalia +(Prochoriata) and the true Simiæ. (3) All +the Catarrhinæ, or Eastern Simiæ, form one +natural monophyletic group. Their hypothetical +common ancestor, the Archipithecus, +may have descended directly or indirectly +from a branch of the Lemures. (4) Man +is descended directly from one series of +extinct Catarrhine ancestors. The more +recent ancestors of this series were tailless +anthropoids (similar to the Anthropopithecus), +with five sacral vertebræ. The +more remote ancestors were tailed Cercopitheci, +with three or four sacral vertebræ.</p> + +<p>These four theses possess, in my opinion, +absolute certainty. They are independent of +all future anatomical, embryological, and +palæontological discoveries which may possibly +throw more light upon the details of +our phyletic anthropogenesis.</p> + +<p><span class="pagenum"><a name="Page_20" id="Page_20">[Pg 20]</a></span></p> + +<hr class="chap"/> +<div class="chapter-beginning"/> +<h2>II.</h2> + + +<p>The next question is, how the facts of +palæontology agree with these most important +results of comparative anatomy and ontogeny. +The fossils are the true historical 'medals of +creation,' the palpable evidence of the historical +succession of all those innumerable +organic forms which have peopled the globe +for many millions of years. Here the question +arises, If the known fossil specimens of Mammalia, +and particularly of Primates, give proof +of these Pithecometra-theses, do they confirm +directly the descent of man from ape-like +creatures? The answer to this question +is, in my opinion, affirmative.</p> + +<p>It is true that the gaps in the palæontological +evidence, here as elsewhere, are<span class="pagenum"><a name="Page_21" id="Page_21">[Pg 21]</a></span> +many and keenly felt. In the order of the +Primates they are greater than in many +other orders, chiefly because of the arboreal +life of our ancestors. The explanation is very +simple. It is really due to a long chain of +favourable coincidences if the skeleton of a +vertebrate, covered as it was with flesh and +skin, and containing still more perishable +viscera, is petrified at all. The body may be +devoured by other creatures, and its bones +scattered about; or it rots away and crumbles +to pieces. Many animals hide in thick undergrowth +when death approaches them; and, +leading an almost entirely arboreal life, the +Primates are especially likely to disappear +without being fossilized. It is only when the +body is quickly covered with sand, or is embedded +in suitable lime or silica containing +mud, that the process of petrifaction can +come to pass. Even then it is only by great +good luck that we come across such a fossil. +Very few countries have been searched +systematically, and the areas that have been<span class="pagenum"><a name="Page_22" id="Page_22">[Pg 22]</a></span> +searched amount to little in comparison with +the whole surface of the land, even if we +leave out of account the fact that more than +two-thirds of the globe are covered by water.</p> + +<p>These deplorable deficiencies of empirical +palæontology are balanced on the other side +by a growing number of positive facts, which +possess an inestimable value in human +phylogeny. The most interesting and most +important of these is the celebrated fossil +<i>Pithecanthropus erectus</i>, discovered in Java +in 1894 by Dr. Eugène Dubois.<a name="FNanchor_10_10" id="FNanchor_10_10"></a><a href="#Footnote_10_10" class="fnanchor">[10]</a> Three +years ago this now famous ape-like man +provoked an animated discussion at the third +International Zoological Congress at Leyden. +I may therefore be allowed to say a few +words as to its scientific significance. Unfortunately, +the fossil remains of this creature +are very scanty: the skull-cap, a femur, and +two teeth. It is obviously impossible to form<span class="pagenum"><a name="Page_23" id="Page_23">[Pg 23]</a></span> +from these scanty remains a complete and +satisfactory reconstruction of this remarkable +Pliocene Primate.</p> + +<p>The more important points are the following: +The remains in question rested upon a +conglomerate which lies upon a bed of marine +marl and sand of Pliocene age. Together +with the bones of Pithecanthropus were found +those of Stegodon, Leptobos, Rhinoceros, Sus, +Felis, Hyæna, Hippopotamus, Tapir, Elephas, +and a gigantic Pangolin. It is remarkable +that the first two of these genera are now +extinct, and that neither hippopotamus nor +hyæna exists any longer in the Oriental region. +If we may judge from these fossil remains, +the bones of Pithecanthropus are not younger +than the oldest Pleistocene, and probably +belong to the upper Pliocene. The teeth +are like those of man. The femur, also, is +very human, but shows some resemblances +to that of the gibbons. Its size, however, +indicates an animal which stood when erect +not less than 5 feet 6 inches high. The<span class="pagenum"><a name="Page_24" id="Page_24">[Pg 24]</a></span> +skull-cap also is very human, but with very +prominent eyebrow ridges, like those of +the famous Neanderthal cranium. It is +certainly not that of an idiot. It had an +estimated cranial capacity of about 1,000 +cubic centimetres—that is to say, much +more than that of the largest ape, which +possesses not more than 600 c.c. The crania +of female Australians and Veddahs measure +not more than 1,100, some even less than +1,000 c.c.; but, as these Veddah women stand +only about 4 feet 9 inches high, the computed +cranial capacity of the much taller Pithecanthropus +is comparatively very low indeed.<a name="FNanchor_11_11" id="FNanchor_11_11"></a><a href="#Footnote_11_11" class="fnanchor">[11]</a></p> + +<div class="figcenter"><a href="./images/i_0331.jpg"> + <img src="./images/i_0331.jpg" alt="Skulls"></img></a> +</div> + +<blockquote> +<p><small>The upper figure represents the outlines of the skull of Pithecanthropus, +as restored by Manouvier.<a name="FNanchor_12_12" id="FNanchor_12_12"></a><a href="#Footnote_12_12" class="fnanchor">[12]</a> The lower figure shows the +comparative size and shape of Pithecanthropus, the Neanderthal +skull, a specimen of the Cro-Magnon race of neolithic France, and a +Young Chimpanzee before the full development of the supraorbital +crests</small>.</p> +</blockquote> + +<p>The final result of the long discussion at +Leyden was that, of twelve experts present, +three held that the fossil remains belonged +to a low race of man; three declared them +to be those of a man-like ape of great size;<span class="pagenum"><a name="Page_25" id="Page_25">[Pg 25]</a><br /><a name="Page_26" id="Page_26">[Pg 26]</a></span> +the rest maintained that they belonged to an +intermediate form, which directly connected +primitive man with the anthropoid apes. +This last view is the right one, and accords +with the laws of logical inference. <i>Pithecanthropus +erectus</i> of Dubois is truly a +Pliocene remainder of that famous group of +highest Catarrhines which were the immediate +pithecoid ancestors of man. He is, indeed, the +long-searched-for 'missing link,' for which, in +1866, I myself had proposed the hypothetical +genus Pithecanthropus, species Alalus.</p> + +<p>It must, however, be admitted that this +opinion is still strongly combated by some +distinguished authorities. At the Leyden +Congress it was attacked by the illustrious +pathologist Rudolf Virchow.<a name="FNanchor_13_13" id="FNanchor_13_13"></a><a href="#Footnote_13_13" class="fnanchor">[13]</a> He, however, +is one of the minority of leading men of +science who set themselves to refute the +theory of Evolution in every possible way. +For thirty years he has defended the thesis: +'It is quite certain that man is not a<span class="pagenum"><a name="Page_27" id="Page_27">[Pg 27]</a></span> +descendant of apes.' He declares any intermediate +form to be unimaginable save in a +dream.</p> + +<p>Virchow went to the Leyden Congress +with the set purpose of disproving that the +bones found by Dubois belonged to a creature +which linked together apes and man. First, +he maintained that the skull was that of an +ape, while the thigh belonged to man. This +insinuation was at once refuted by the expert +palæontologists, who declared that without +the slightest doubt the bones belonged to +one and the same individual. Next, Virchow +explained that certain exostoses or growths +observable on the thigh proved its human +nature, since only under careful treatment +the patient could have healed the original +injury. Thereupon Professor Marsh, the +celebrated palæontologist, exhibited a number +of thigh-bones of wild monkeys which +showed similar exostoses and had healed +without hospital treatment. As a last argument +the Berlin pathologist declared that<span class="pagenum"><a name="Page_28" id="Page_28">[Pg 28]</a></span> +the deep constriction behind the upper +margin of the orbits proved that the skull +was that of an ape, as such never occurred in +man. It so happened that a few weeks later +Professor Nehring of Berlin demonstrated +exactly the same formation on a human prehistoric +skull received by him from Santos, +in Brazil.</p> + +<p>Virchow was, in fact, just as unlucky in +Leyden in his fight with our pliocene +ancestor as he had been unfortunate in his +opinion on the famous skulls of Neanderthal, +Spy, La Naulette, etc., every one of which he +explained as a pathological abnormality. It +would be a very curious coincidence indeed if +all these and other fossil human remains +were those of idiots or otherwise abnormal +individuals, provided they are old and low +enough in their organization to be of phylogenetic +value to the unbiassed zoologist.</p> + +<p>As the sworn adversary of Evolution, +transformism, and Darwinism in particular, +but a believer in the constancy of species, the<span class="pagenum"><a name="Page_29" id="Page_29">[Pg 29]</a></span> +great and renowned pathologist has been +driven to the incredible contention that all +variations of organic forms are pathological.</p> + +<p>Four years ago, as honorary president of +the Anthropological Congress at Vienna, he +attacked Darwinism in the severest manner, +and declared that 'man may be as well +descended from the elephant or from the +sheep as from the ape.' Such attacks on the +theory of transformism indicate a failure to +understand the principles of the theory of +Evolution and to appreciate the significance +of palæontology, comparative anatomy, and +ontogeny.</p> + +<p>The thousands of other objections which +have been made during the last forty years +(chiefly by outsiders) may be passed over in +silence. They do not require serious refutation. +In spite of, or perhaps because of, +these attacks, the theory of Evolution stands +established more firmly than ever.</p> + +<p>It is easy for the outsider to exult over the +difficulties which our problem implies—diffi<span class="pagenum"><a name="Page_30" id="Page_30">[Pg 30]</a></span>culties +which we who have given our lives to +the study understand likewise, and try our +best not only to bridge over, but also to +point out. Anyhow, we do not conceal +them; while those who reject the explanation +offered by Evolution make the most of the +gaps, and pass silently over the far more +numerous points favourable to our theory.</p> + +<p>How fruitful during the last thirty years +the astonishing progress in our palæontological +knowledge has been for our Pithecometra-thesis +is best shown by a short glance +at the growth of our knowledge of fossil +Primates. Cuvier,<a name="FNanchor_14_14" id="FNanchor_14_14"></a><a href="#Footnote_14_14" class="fnanchor">[14]</a> the founder of palæontology, +continued up to the time of his death, +in 1832, to assert that fossil remains of +monkeys and lemurs did not exist. The +only skull of a fossil lemuroid which he described +(namely, Adapis) he declared to be +that of an ungulate. Not until 1836 were +the first fragments of extinct monkeys found +in India; it was two years later, near Athens,<span class="pagenum"><a name="Page_31" id="Page_31">[Pg 31]</a></span> +that the skeleton of <i>Mesopithecus penthelicus</i> +was discovered. Other remains of lemurs +were found in 1862. But during the last +twenty years the number of fossil Primates +has been augmented by the remarkable discoveries +of Gaudry, Filhol, Milne Edwards, +Seeley, Schlosser, and others in Europe; of +Marsh, Cope, Osborn, Leidy, Ameghino, in +South America; and Forsyth Major in +Madagascar.<a name="FNanchor_15_15" id="FNanchor_15_15"></a><a href="#Footnote_15_15" class="fnanchor">[15]</a> These tertiary remains, chiefly<span class="pagenum"><a name="Page_32" id="Page_32">[Pg 32]</a></span> +of Eocene and Miocene date, fill many gaps +between existing genera of Primates, and +afford us quite a clear insight into the phyletic +development of this order during the +millions of years of the Cænozoic age.</p> + +<p>The most important difference between the +two groups of existing monkeys is indicated +by their dentition. Adult man possesses, +like all the other Catarrhine Simiæ, thirty-two +teeth, whilst the American monkeys (the +Platyrrhinæ) have thirty-six teeth—namely, +one pair of premolars more in the upper and +lower jaws. Comparative odontology leads +us to the phylogenetic conclusion that this +number has been produced by reduction from +a still older form with forty-four teeth. This +typical dental formula (three incisors, one +canine, four premolars, and three molars, in +each half-jaw) is common to all those most +important older mammals which in the beginning +of the Eocene period constituted the four +large groups of Lemuravida, Condylarthra, +Esthonychida, and Ictopsida. These are the<span class="pagenum"><a name="Page_33" id="Page_33">[Pg 33]</a></span> +four ancestral groups of the four main orders +of Placentalia—namely, of the Primates, +Ungulata, Rodentia, and Carnassia. They +seem to be so closely related by their primitive +organization that they may be united in +one common super-order, Prochoriata.</p> + +<p>With a considerable degree of probability, +we are led to formulate the further +hypothesis that all the orders of Placentalia—from +the lowest Prochoriata upwards to +man—have descended from some unknown +common ancestor living in the Cretaceous +period, and that this oldest placental form +originated from some Jurassic group of +marsupials.</p> + +<p>Among these numerous fossil Lemures +which have been discovered within the last +twenty years, there exist, indeed, all the connecting +forms of the older series of Primates, +all the 'missing links' sought for by comparative +odontology.</p> + +<p>The oldest Lemures of the tertiary age +are the Eocene Pachylemures, or Hyopso<span class="pagenum"><a name="Page_34" id="Page_34">[Pg 34]</a></span>dina. +They possess the complete dentition +of the Prochoriata—namely, forty-four teeth +(3.1.4.3/3.1.4.3). Then follow the Eocene Palæolemures, +or Adapida, with forty teeth, they +having lost one pair of incisors in each jaw. +To these are attached the younger Autolemures, +or Stenopida, with thirty-six teeth, +they thus possessing already the same dentition +as the Platyrrhinæ. The characteristic +dentition of the Catarrhinæ is derived from +this formula by the loss of another premolar.</p> + +<p>These relations are so clear and so closely +connected with a gradual transformation of +the whole skull, and with the progressive +differentiation of the Primate-form, that we +are justified in saying that the pedigree of the +Primates, from the oldest Eocene Lemures +upwards to man, is now so well known, its +principal features so firmly fixed within the +Tertiary age, that there is no missing link +whatever.</p> + +<p>Quite different, and much more incom<span class="pagenum"><a name="Page_35" id="Page_35">[Pg 35]</a></span>plete, +is the palæontological evidence, if we +go further back into the Secondary or Mesozoic +age, and look there for the older ancestors +of the mammalian series. There we +meet everywhere with wide gaps, and the +scarce fragments of fossil Mesozoic mammals +(excessively rare in the Cretaceous formation) +are too poor to permit definite conclusions as +to their systematic position. Indeed, comparative +anatomy and ontogeny lead us to the +hypothesis that the oldest Cretaceous Mammalia—the +Prochoriata—are descended from +Jurassic marsupials, and these again from +Monotremes. We may also suppose with +high probability that among the unknown +Cretaceous Prochoriata there have been +Lemuravida and forms intermediate between +these and the Jurassic Amphitheriidæ, and +that these marsupials in their turn are descendants +of Pantotheria or similar monotreme-like +creatures of the Triassic age. Any +certain evidence for these hypotheses is at +present still wanting. One important fact,<span class="pagenum"><a name="Page_36" id="Page_36">[Pg 36]</a></span> +however, is established—namely, that these +interesting and oldest Mammalia—the Pantotheria +of Marsh, the Triassic Dromatheriidæ, +and the Jurassic Triconodontidæ of Osborn—were +small insectivorous mammals with a very +primitive organization. Probably they were +Monotremes, and may be derived directly +from Permian Sauromammalia, an ill-defined +mixture of Mammalia and Reptilia.</p> + +<p>This generalized characteristic supports +our view that <i>the whole class of Mammalia is +monophyletic</i>, and that all its members, from +the oldest Monotremes upwards to man, have +descended from one common ancestor living +in the older Triassic, or perhaps in the +Permian, age. To acquire full conviction of +this important conception, we have only to +think of the hair and the glands of our +human skin, of our diaphragm, the heart and +the blood corpuscles without a nucleus, our +skull with its squamoso-mandibular articulation. +All these singular and striking modifications +of the vertebrate organization are<span class="pagenum"><a name="Page_37" id="Page_37">[Pg 37]</a></span> +common to mammals, and distinguish them +clearly from the other Craniota. This characteristic +combination and correlation proves +that they have been developed only <i>once</i> in +the history of the vertebrate stem, and that +they have been transferred by heredity from +one common ancestor to all the members of +the class of Mammalia.</p> + +<p>The next step, as we trace our human +phylogeny to its origin, leads us further back +into the lower Vertebrata, into that obscure +Palæozoic age the immeasurable length of +which (much greater than that of the +Mesozoic) may, according to one of the +newest geological calculations, have comprised +about one thousand millions of years.<a name="FNanchor_16_16" id="FNanchor_16_16"></a><a href="#Footnote_16_16" class="fnanchor">[16]</a></p> + +<p>The first important fact we have to face +here is the complete absence of mammalian +remains. Instead of these we find in the +later Palæozoic period, the Permian, air-breathing +<i>reptiles</i> as the earliest representatives +of Amniota. They belong to the<span class="pagenum"><a name="Page_38" id="Page_38">[Pg 38]</a></span> +most primitive order of that class, the +Tocosauria; and besides them there were +the Theromorpha, which approach the Mammalia +in a remarkable manner. These +reptiles in turn were preceded, in the Carboniferous +period, by true Amphibia, most +of them belonging to the armour-clad +Stegocephali. These interesting Progonamphibia +were the oldest Tetrapoda, the first +vertebrates which had adapted themselves +to the terrestrial mode of life; in them the +swimming fin of fishes and Dipneusta was +transformed into the pentadactyle extremities +characteristic of quadrupeds.</p> + +<p>To appreciate the high importance of this +metamorphosis, we need only compare the +skeleton of our own human limbs with that +of the living Amphibia. We find in the +latter the same characteristic composition +as in man: the same shoulder and pelvic +girdle; the same single bone, the humerus +or the femur, followed by the same pair of +bones in the forearm and leg; then the same<span class="pagenum"><a name="Page_39" id="Page_39">[Pg 39]</a></span> +skeletal elements composing the wrist and +the ankle regions; and, lastly, the same five +fingers and toes.</p> + +<p>The arrangement of these bones, peculiar +and often complicated, but everywhere +essentially the same in all the Tetrapoda, +is a striking evidence that man is a +descendant from the oldest pentadactyle +Amphibia of the Carboniferous period. In +man the pentadactyle type has been better +preserved by constant heredity than in many +other Mammalia, notably the Ungulata.</p> + +<p>The oldest Carboniferous Amphibia, the +armour-clad Stegocephali, and especially the +remarkable Branchiosauri discovered by +Credner, are now regarded by all competent +zoologists as the indubitable common ancestral +group of all Tetrapoda, comprising both +Amphibia and Amniota. But whence this +most remote group of Tetrapoda? That +difficult question is answered by the marvellous +progress of modern palæontology, and +the answer is in complete harmony with<span class="pagenum"><a name="Page_40" id="Page_40">[Pg 40]</a></span> +the older results arrived at by comparative +anatomy and ontogeny. Thirty-four years +ago Carl Gegenbaur,<a name="FNanchor_17_17" id="FNanchor_17_17"></a><a href="#Footnote_17_17" class="fnanchor">[17]</a> the great living master +of comparative anatomy, had demonstrated +in a series of works how the skeletal +parts of the various classes of Vertebrata, +especially the skull and the limbs, still represent +a continuous scale of phyletic gradations. +Apart from the Cyclostomes, there are the +fishes, and among them the Elasmobranchi +(sharks and rays), which have best preserved +the original structure in all its essential parts +of organization. Closely connected with the +Elasmobranchi are the Crossopterygii, and +with these the Dipneusta or Dipnoi. Among +the latter the highest importance attaches +to the ancient Australian Ceratodus. Its +organization and development is now, at +last, becoming well known. This transitional +group of Dipnoi, 'fishes with lungs' +but without pentadactyle limbs, is the +morphological bridge which joins the<span class="pagenum"><a name="Page_41" id="Page_41">[Pg 41]</a></span> +Ganoids and the oldest Amphibia. With +this chain of successive groups of Vertebrata, +constructed anatomically, the palæontological +facts agree most satisfactorily. +Selachians and Ganoids existed in the +Silurian times, Dipnoi in the Devonian, +Amphibia in the Carboniferous, Reptilia in +the Permian, Mammalia in the Trias. These +are historical facts of first rank. They +connote in the most convincing manner that +remarkable ascending scale in the series of +vertebrates for our knowledge of which we +are indebted to the works of Cuvier and +Blainville, Meckel, Johannes Mueller and +Gegenbaur, Owen and Huxley. The historical +succession of the classes and orders +of the Vertebrata in the course of untold +millions of years is definitely fixed by the +concordance of those leading works, and this +invaluable acquisition is much more important +for the foundation of our human +pedigree than would be a complete series of +all possible skeletons of Primates.</p> + +<p><span class="pagenum"><a name="Page_42" id="Page_42">[Pg 42]</a></span></p> + +<p>Greater and more frequent difficulties +arise if we penetrate further into the most +remote part of the human phylogeny, and +attempt to derive the vertebrate stem from +an older stem of invertebrate ancestors. +None of those had a skeleton which could be +petrified; and the same remark applies to +the lowest classes of Vertebrata—to the +Cyclostomes and the Acrania. Palæontology, +therefore, can tell us nothing about them; +and we are limited to the other two great +documents of phylogeny—the results of comparative +anatomy and ontogeny. The value +of their evidence is, however, so great that +every competent zoologist can perceive the +most important features of the most remote +portion of our phylogeny.</p> + +<p>Here the first place belongs to the invaluable +results which modern comparative +ontogeny has gained by the aid of the +biogenetic law or the theory of recapitulation. +The foundation-stones of vertebrate embryology +had been laid by the works of Von<span class="pagenum"><a name="Page_43" id="Page_43">[Pg 43]</a></span> +Baer, Bischoff,<a name="FNanchor_18_18" id="FNanchor_18_18"></a><a href="#Footnote_18_18" class="fnanchor">[18]</a> Remak, and Koelliker;<a name="FNanchor_19_19" id="FNanchor_19_19"></a><a href="#Footnote_19_19" class="fnanchor">[19]</a> but +the clearest light was thrown upon it by the +famous discoveries of Kowalevsky<a name="FNanchor_20_20" id="FNanchor_20_20"></a><a href="#Footnote_20_20" class="fnanchor">[20]</a> in 1866. +He proved the identity of the first developmental +stages of Amphioxus and +the Ascidians, and thereby confirmed the +divination of Goodsir, who had already +announced the close affinity of Vertebrates +and Tunicates. The acknowledgment of +this affinity has proved of increasing importance, +and has abolished the erroneous +hypothesis that the Vertebrata may have +arisen from Annelids or from other Articulata. +Meanwhile, from 1860 to 1872, I +myself had been studying the development +of the Spongiæ, Medusæ, Siphonophora, and +other Cœlenterata. Their comparison led +me to the statements embodied in the<span class="pagenum"><a name="Page_44" id="Page_44">[Pg 44]</a></span> +'Gastræatheorie,' the first abstract of which +was published in 1872 in my monograph of +the Calcispongiæ.</p> + +<p>These ideas were carried on and expanded +during the subsequent ten years by +the help of many excellent embryologists—first +of all by E. Ray Lankester and Francis +Balfour. The most fruitful result of these +widely extended researches was the conclusion +that the first stages of embryonic +development are essentially the same in all +the different Metazoa, and that we may +derive from these facts certain views on the +common descent of all from one ancestral +form. The unicellular egg<a name="FNanchor_21_21" id="FNanchor_21_21"></a><a href="#Footnote_21_21" class="fnanchor">[21]</a> repeats the stage +of our Protozoan ancestors; the Blastula is +equivalent to an ancestral cœnobium of +Magosphæra or Volvox; the Gastrula is +the hereditary repetition of the Gastræa, the +common ancestor of all the Metazoa.</p> + +<p>Man agrees in all these respects with the +other vertebrates, and must have descended +with them from the same common root.</p> + +<p><span class="pagenum"><a name="Page_45" id="Page_45">[Pg 45]</a></span></p> + +<p>Particularly obscure is that part of our +phylogeny which extends from the Gastræa +to Amphioxus. The morphological importance +of this last small creature had been +perceived by Johannes Mueller, who in 1842 +gave the first accurate description of it. It +would not, of course, be correct to proclaim +the modern Amphioxus the common ancestor +of all the vertebrates; but he must be regarded +as closely related to them, and as the only +survivor of the whole class of Acrania. If +the Amphioxidæ had through some unfortunate +accident become extinct, we should +not have been able to gain anything like a +positive glimpse at our most remote vertebrate +ancestor. On the one hand, Amphioxus is +closely connected with the early larva of the +Cyclostomes, which are the oldest Craniota, +and the pre-Silurian ancestors of the fishes. +On the other hand, the ontogeny of Amphioxus +is in harmony with that of the Ascidians, +and if this agreement is not merely coincidental, +but due to relationship, we are +justified in reconstructing for both Ascidians<span class="pagenum"><a name="Page_46" id="Page_46">[Pg 46]</a></span> +and Amphioxus one common ancestral group +of chordate animals, the hypothetical <i>Prochordonia</i>. +The modern Copelata give us +a remote idea of their structure. The curious +Balanoglossus, the only living form of Enteropneusta, +seems to connect these Prochordonia +with the Nemertina and other Vermalia, +which we unite in one large class—Frontonia.</p> + +<p>No doubt these pre-Cambrian Vermalia, +and the common root of all Metazoa, the +Gastræades, were connected during the +Laurentian period by a long chain of intermediate +forms, and probably among these +were some older forms of Rotatoria and +Turbellaria; but at present it is not possible +to fill this wide gap with hypotheses that +are satisfactory, and we have to admit that +here indeed are many missing links in the +older history of the Invertebrata. Still, +every zoologist who is convinced of the truth +of transformism, and is accustomed to phylogenetic +speculations, knows very well that +their results are most unequal, often incomplete.</p> + +<p><span class="pagenum"><a name="Page_47" id="Page_47">[Pg 47]</a></span></p> + +<hr class="chap"/> +<div class="chapter-beginning"/> +<h2>III.</h2> + + +<p>Let us now recapitulate the ancestral chain +of man, as it is set forth in the accompanying +diagram (p. <a name="FNanchor_55_55" id="FNanchor_55_55"></a><a href="#Footnote_55_55" class="label">55</a>), which represents our present +knowledge of our descent. For simplicity's +sake the many side-issues or branches which +lead to groups not in the main line of our +descent have been left out, or have been indicated +merely. Many of the stages are of +course hypothetical, arrived at by the study +of comparative anatomy and ontogeny; but +an example for each of them has been taken +from those living or fossil creatures which +seem to be their nearest representatives.</p> + +<p>1. The most remote ancestors of all living +organisms were living beings of the simplest +imaginable kind, organisms without organs,<span class="pagenum"><a name="Page_48" id="Page_48">[Pg 48]</a></span> +like the still existing <i>Monera</i>. Each consisted +of a simple granule of protoplasm, a +structureless mass of albuminous matter or +plasson, like the recent Chromaceæ and +Bacteriæ. The morphological value of these +beings is not yet that of a cell, but that of a +cytode, or cell without a nucleus. Cytoplasm +and nucleus were still undifferentiated.</p> + +<p>I assume that the first Monera owe their +existence to spontaneous creation out of so-called +anorganic combinations, consisting of +carbon, hydrogen, oxygen, and nitrogen. An +explanation of this hypothesis I have given +in my 'Generelle Morphologie.'</p> + +<p>The Monera probably arose early in the +Laurentian period. The oldest are the +Phytomonera, with vegetable metabolism. +They possessed the power (characteristic of +plants) of forming albumin by synthesis from +carbon, water, and ammonia. From some of +these plasma-forming Monera arose the +plasmophagous Zoomonera with animal metabolism, +living directly upon the produce of<span class="pagenum"><a name="Page_49" id="Page_49">[Pg 49]</a></span> +their plasmodomous or plasma-forming +sisters. This is the first instance of the +great principle of division of labour.</p> + +<p>2. The second stage is that of the <i>simple +and single cell</i>, a bit of protoplasm with a +nucleus. Such unicellular organisms are +still very common. The <i>Amœbæ</i> are their +simplest representatives. The morphological +value of such beings is the same as that of +the egg of any animal. The naked egg cells +of the sponges creep about in an amœboid +fashion, scarcely distinguishable from Amœba. +The same remark applies to the egg-cell of +man himself in its early stages before it is +enclosed in a membrane. The first unicellular +organisms arose from Monera through differentiation +of the inner nucleus from the outer +protoplasm.</p> + +<p>3. Repeated division of the unicellular +organism produces the <i>Synamœbium</i>, or +community of Amœbæ, provided the divisional +products, or new generations of the +original cell, do not scatter, but remain<span class="pagenum"><a name="Page_50" id="Page_50">[Pg 50]</a></span> +together. The existence of such a <i>Cœnobium</i>, +a number of equal and only loosely-connected +cells, as a separate stage in the ancestral +history of animals, is made highly probable by +the fact that the eggs of all animals undergo +after fertilization such a process of repeated +self-division, or 'cleavage,' until the single +egg cell is transformed into a heap of cells +closely packed together, not unlike a mulberry +(<i>morula</i>)—hence <i>morula</i> stage in ontogeny.</p> + +<p>4. The morula of most animals further +changes into a <i>Blastula</i>, a hollow ball filled +with fluid, the wall being formed by a single +layer of cells, the blastoderm or germinal layer. +This modification is brought about by the +action of the cells—they conveying nourishing +fluid into the interior of the whole cell +colony and thereby being themselves forced +towards the surface. The Blastula of most +Invertebrata, and even that of Amphioxus, is +possessed of fine ciliæ, or hair-like processes, +the vibrating motion of which causes the +whole organism to rotate and advance in<span class="pagenum"><a name="Page_51" id="Page_51">[Pg 51]</a></span> +the water. Living representatives of such +Blastæads, namely, globular gelatinous +colonies of cells enclosing a cavity, are +Volvox and Magosphæra.</p> + +<p>5. The Blastula of most animals assumes +a new larval form called <i>Gastrula</i>, in which +the essential characteristics are that a portion +of the blastoderm by invagination converts +the Blastula into a cup with double walls, +enclosing a new cavity, the primitive gut. +This invagination or bulging-in obliterates +the original inner cavity of the Blastula. +The outer layer of the Gastrula is the ectoderm, +the inner the endoderm; both pass +into each other at the blastoporus, or opening +of the gut cavity. The Gastrula is a stage +in the embryonic development of the various +great groups of animals, and some such +primitive form as ancestral to all Metazoa is +thus indicated. This hypothetical <i>Gastræa</i> +is still very essentially represented by the +lower Cœlenterates—<i>e.g.</i>, Olynthus, Hydra.</p> + +<p>6. The sixth stage—that of the <i>Platodes</i>,<span class="pagenum"><a name="Page_52" id="Page_52">[Pg 52]</a></span> +or flat-worms—is very hypothetical. They +are bilateral gastræads, with a flattened +oblong body, furnished with ciliæ, with a +primitive nervous system, simple sensory and +reproductive organs, but still without appendages, +body cavity, vent, and blood-vessels. +The nearest living representatives of such +creatures are the acœlous Turbellarians—<i>e.g.</i>, +Convoluta, a free-swimming, ciliated creature.</p> + +<p>7. The next higher stage is represented +by such low animals as the <i>Gastrotricha</i>—<i>e.g.</i>, +Chætonotus among the Rotatoria, which +differ from the rhabdocœlous Turbellarians +chiefly by the formation of a vent and the +beginnings of a cœlom, or cavity, between +gut and body wall. The addition of a primitive +vascular system and a pair of nephridia, +or excretory organs, is first met with in the +<i>Nemertines</i>.</p> + +<p>8. These, together with the <i>Enteropneusta</i> +(Balanoglossus), are comprised under the +name of Frontonia, or Rhynchelminthes, +and form the highest group of the Vermalia.</p> + +<p><span class="pagenum"><a name="Page_53" id="Page_53">[Pg 53]</a></span></p> + +<p>The Enteropneusta especially fix our attention, +because they alone, although essentially +'worms,' exhibit certain characteristics which +make it possible to bridge over the gulf +which still separates the Invertebrata from +the vertebrate phylum. The anterior portion +of the gut is transformed into a breathing +apparatus—hence Gegenbaur's term of Enteropneusta, +or Gut-breathers. Moreover, +Balanoglossus and Cephalodiscus possess +another modification of the gut—namely, a +peculiar diverticulum, which, in the present +state of our knowledge, may be looked upon +as the forerunner of the chorda dorsalis.</p> + +<p>9. Stage of <i>Prochordonia</i>, as indicated by +the larval form, called Chordula, which is +common to the Tunicata and all the Vertebrata. +These two groups possess three most +important features: (<i>a</i>) A chorda dorsalis, +a stiff rod lying in the long axis of the +body, dorsally from the gut and below the +central nervous system. This latter, for the +first time in the animal kingdom, appears in<span class="pagenum"><a name="Page_54" id="Page_54">[Pg 54]</a></span> +the shape of a spinal cord. (<i>b</i>) The use of +the anterior portion of the gut for respiratory +purposes. (<i>c</i>) The larval development of +the Tunicata is essentially the same as that of +the Vertebrata in its early stages. Only the +free-swimming Copelata or Appendicularia +among the Tunicates retain most of these +features. The others, which become sessile—namely, +the Ascidiæ, or sea-squirts—degenerate +and specialize away from the +main line.</p> + +<p class="center"> +<a name="Footnote_55_55" id="Footnote_55_55"></a><a href="#FNanchor_55_55"><span class="label">ANCESTRAL TREE OF THE VERTEBRATA</span></a><br /> +<i>Abridged from 'Systemat. Phylogenie,' § 15.</i><br /> +Names underlined refer to hypothetical groups.</p> + +<table id="atv" summary="vertebrata"> + +<tr> + <td class="tdc"><i>Aves</i></td> + <td class="tdc"> </td> + <td class="tdc"><i>Mammalia</i></td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdc"><i>Reptilia</i></td> + <td class="tdc">|</td> +</tr> +<tr> + <td class="tdr">'———</td> + <td class="tdl">———|</td> + <td class="tdc">|</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdr">|———</td> + <td class="tdl">———'</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdc">|</td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdc"><i>Proreptilia</i></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdc"><i>Pisces</i></td> + <td class="tdc">|</td> + <td class="tdc"><i>Amphibia</i></td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdr">|———</td> + <td class="tdl">———'</td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdc"><i>Stegocephali</i></td> + <td class="tdc"><i>Dipnoi</i></td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdr">|———</td> + <td class="tdl">———'</td> +</tr> +<tr> + <td class="tdr">'———</td> + <td class="tdl">———|</td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdc"><i>Proselachii</i></td> + <td class="tdc"><i> Cyclostomata</i></td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdc">|</td> + <td class="tdc">|</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdr">|———</td> + <td class="tdl">———'</td> +</tr> +<tr> + <td class="tdl"> </td> + <td class="tdc">|</td> + <td class="tdr"> </td> +</tr> +<tr> + <td class="tdc"> <i>Tunicata</i> </td> + <td class="tdc"> <span class="u"><i>Archicrania</i></span></td> + <td class="tdc"><i>Acrania</i></td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdr">|———</td> + <td class="tdl">———'</td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdc"><span class="u"><i>Prospondylia</i></span></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdr">'———</td> + <td class="tdl">———|</td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdc"><span class="u"><i>Prochordonia</i> </span></td> + <td class="tdr"></td> +</tr> +</table> + +<p>10. Stage of the <i>Acrania</i>, represented by +Amphioxus. The early development of this +little marine creature agrees closely with that +of the Tunicates; but one important feature +is added to its organization—namely, metamerism, +segmentally arranged mesoderm. +Amphioxus still possesses neither skull nor +vertebræ, neither ribs nor jaws, and no limbs. +But it is a member of the Vertebrata if we +define these as follows: Bilateral symmetrical +animals with segmentally arranged mesoderm, +with a chorda dorsalis between the +<span class="pagenum"><a name="Page_55" id="Page_55">[Pg 55]</a></span> +<span class="pagenum"><a name="Page_56" id="Page_56">[Pg 56]</a></span> +tubular nervous system and the gut, and with +respiratory organs which arise from the anterior +portion of the gut. We do not assume +that Amphioxus stands in the direct ancestral +line; it is probably much specialized, partly +degenerated, and represents a side-branch; +but it is, nevertheless, the only creature, +hitherto known, which satisfactorily connects +the Vertebrata with their invertebrate ancestors. +Many other efforts have been made to +solve the mystery of the origin of the Vertebrata—all +less satisfactory than the present +suggestion, or even absolutely futile. This +remark applies especially to the attempts +to derive them from either Articulata or +Echinoderms. The other great and highly +developed phylum, the Mollusca, is quite +out of the question. We have to go back to +a level at which all these principal phyla +meet, and there we find the Vermalia, the +lower of which alone permit connection in an +upward direction with the higher phyla.</p> + +<p>11. Stage of <i>Cyclostomata</i>. This now<span class="pagenum"><a name="Page_57" id="Page_57">[Pg 57]</a></span> +small group of Lampreys and Hagfishes +represents the lowest Craniota; and although +much specialized as a side-branch of the +main-stem from which the other Craniota +have sprung, they give us an idea of what +the direct ancestors of the latter must have +been like:—still without visceral arches, +without jaws and without paired limbs; with +a persistent pronephros; the ear with one +semicircular canal only; mouth suctorial; +cranium very primitive; and the metamerism +of the vertebral column indicated only by +little blocks of cartilage in the perichordal +sheath. Such creatures must have existed +at least as early as the Lower Silurian +epoch; but until 1890 fossil Cyclostomes were +unknown. Their life in the mud, or as +endoparasites of fishes, coupled with their +soft structure, makes them very unfit for +preservation. This gives all the greater importance +to Traquair's discovery, in 1890, of +many little creatures, called by him <i>Palæospondylus +gunni</i>, in the Old Red Sandstone of<span class="pagenum"><a name="Page_58" id="Page_58">[Pg 58]</a></span> +Caithness, which seem to be very closely +allied to Cyclostomata.</p> + +<p>12. The <i>Elasmobranchi</i> (sharks and skates), +with their immediate forerunners, the Acanthodi +of the Devonian and Carboniferous age, +are the first typical fishes. That they existed +as far back as the Silurian age is proved by +many enamelled spines of the dermal armour, +chiefly from the dorsal fins. This higher +stage is characterized by the possession of +typical jaws, by visceral or gill-bearing arches, +and by two pairs of limbs. None of the +Elasmobranchs, fossil or recent, stands in the +direct ancestral line; but they are the lowest +Gnathostomata, jaw-and-limb-possessing +creatures, known.</p> + +<p>13. Closely connected with the Elasmobranchs +in a wider sense are the <i>Crossopterygii</i>, +which begin in the Devonian age as a +large group, but have left only two survivals, +the African Polypterus and Calamoichthys. +They are possessed of dermal bones and +other ossifications, and are characterized by<span class="pagenum"><a name="Page_59" id="Page_59">[Pg 59]</a></span> +their lobate paired fins, which have a thick +axis beset with biserial fin rays. Their gill-clefts +are covered by an operculum, and they +have a well-developed air-bladder. Whilst +they are in many respects more highly +developed than the Elasmobranchs, and are +intimately connected with the typical Ganoids +and other bony fishes (all of which form a +great, manifold side-branch of the general +vertebrate stem), they stand in many other +respects (notably, the structure of the paired +fins, the vertebral column, and the air-bladder) +nearer the main-stem of our own +ancestral line.</p> + +<p>14. This is shown by their intimate +relation to the <i>Dipnoi</i>, which are still represented +by the Australian, African, and South +American mud-fishes: Ceratodus, Protopterus, +and Lepidosiren. The genus Ceratodus +existed in the Upper Trias, whence various +other unmistakably dipnoous forms lead down +through the Carboniferous (<i>e.g.</i>, Ctenodus) +to the Devonian strata—<i>e.g.</i>, Dipterus. They<span class="pagenum"><a name="Page_60" id="Page_60">[Pg 60]</a></span> +are characterized as follows: The paired fins +still retain the archipterygial form (namely, +one axis with biserial rays); the heart is +already trilocular, and receives blood which +is mixed arterial and venous, owing to the +gills being retained, while the air-bladder has +been modified into a lung. In fact, the +generalized Dipnoi form the actual link between +fishes and <i>Amphibia</i>.</p> + +<p>15. <i>Amphibia.</i> The earliest amphibian +fossils occur in the Carboniferous strata. +They alone—the Stegocephali or Phractamphibia—stand +in the ancestral line, while the +Lissamphibia, to which all the recent forms +belong, are side-branches. The Stegocephali +are the earliest Tetrapoda, the archipterygial +paired fins having been transformed into +the pentadactyle fore and hind limbs, which +are so characteristic of all the higher Vertebrata. +The cranium is roofed over by dermal +bones, of which, besides others, supra-occipitals, +supra-orbitals, and supra-temporals +are always present. The lowest members<span class="pagenum"><a name="Page_61" id="Page_61">[Pg 61]</a></span> +(Branchiosauri) still retained gills besides +the lungs, while others (Microsauri) have +lost the gills. Be it remembered that all the +recent Amphibia still undergo the same metamorphosis +during their ontogenetic development.</p> + +<p>In the very important Temnospondyli, a +subgroup of the Stegocephali—<i>e.g.</i>, Trimerorhachis +of the Lower Red Sandstone or Lower +Permian—the component cartilaginous or +bony units which compose the vertebræ still +remained in a separate, unfused state, showing +at the same time an arrangement whence +has arisen that which is typical of the Amniota. +The same applies to the limbs and +their girdles. In fact, the Stegocephali, taken +as a whole, lead imperceptibly to the <i>Proreptilia</i>.</p> + +<p>16. <i>Proreptilia</i> are represented by the +Permian genera Eryops and Cricotus. Until +quite recently these and many other fossils +from the Carboniferous strata were looked +upon as Amphibia, while many undoubted<span class="pagenum"><a name="Page_62" id="Page_62">[Pg 62]</a></span> +fossil Amphibia were mistaken for reptiles, +as indicated by the frequent termination +'-saurus' in their names.</p> + +<p>The nearest living representative of these +extinct Proreptilia is the New Zealand +reptile Hatteria, or Sphenodon, close relations +of which are known from the Upper Trias; +while others—<i>e.g.</i>, Palæohatteria—have been +discovered in the Permian. Anyhow, Sphenodon +is the reptile which stands nearest to the +main stem of our ancestry.</p> + +<p>The most important characteristics of the +Reptilia, which mark a higher stage or level, +are (1) The entire suppression of the gills—although +during the embryonic development +the gill-clefts still appear in all reptiles, birds, +and mammals; (2) The development of an +amnion and an allantois, both for the embryonic +life only, but so characteristic that all +these animals are comprised under the name +of Amniota; (3) The articulation of the skull +with the first neck vertebræ by well-developed +condyles, either single (really triple) or<span class="pagenum"><a name="Page_63" id="Page_63">[Pg 63]</a></span> +double (such a condylar arrangement begins +with the Amphibia, but only the two lateral +condyles are developed, while the middle +portion, belonging to the basi-occipital element, +remains rudimentary<a name="FNanchor_22_22" id="FNanchor_22_22"></a><a href="#Footnote_22_22" class="fnanchor">[22]</a>); (4) The formation +of centra, or bodies of the vertebræ, +mainly by a ventral pair of the original quadruple +constituents, or arcualia.</p> + +<p>17. Between the Proreptilia and the Mammalia, +which latter occur in the Upper Triassic +epoch, we have necessarily to intercalate a +group of very low reptiles, which are still so +generalized that their descendants could +branch off either into the Reptilia proper or +into the Mammalia. The changes concerned +chiefly the brain and the heart; of the skele<span class="pagenum"><a name="Page_64" id="Page_64">[Pg 64]</a></span>ton, +the skull and the pelvis; and, of the +tegumentary structures, the formation of a +hairy covering. Many such creatures existed +in the Triassic epoch—namely, the <i>Theromorpha</i>—some +of which indeed possess so +many characteristics which otherwise occur +in the Mammalia only, that these creatures +have been termed <i>Sauro-Mammalia</i>. However, +it has to be emphasized that none of +the Theromorpha hitherto discovered fulfils +all the requirements which would entitle them +to this important linking position. They only +give us an approximate idea of what this link +was like.</p> + +<p>18. Stage of the <i>Promammalia</i>, or <i>Prototheria</i>. +The only surviving members are +the famous duck-bill, Ornithorhynchus, and +the spiny ant-eaters, Echidna and Proechidna, +of the Australian region. These few genera, +however, differ so much from one another in +various important respects that they cannot +but be remnants of an originally much larger +group. Indeed, many fossils from the Upper<span class="pagenum"><a name="Page_65" id="Page_65">[Pg 65]</a></span> +Triassic and from the Jurassic strata have +without much doubt to be referred to the +Prototheria. The Prototheria are typical +mammals, because they possess the following +characteristics: The heart is completely +quadrilocular; the blood is warm, and its red +corpuscles have, owing to the loss of their +nucleus, been modified from biconvex into +biconcave discs; they have a hairy coat and +sweat glands, and two occipital condyles; the +ilio-sacral connection is preacetabular; the +ankle-joint is cruro-tarsal; the quadrate bone +of the Reptilia has ceased to carry the under +jaw, which now articulates directly with the +squamosal portion of the skull. Their low +position is shown by the retention of the +following reptilian features: Complete coracoid +bones and a T-shaped interclavicle; a +cloaca, or common chamber for the passage +of the fæces, the genital and the urinary products; +they are still oviparous; the embryo +develops without a chorion, and is therefore +not nourished through a placenta. Even the<span class="pagenum"><a name="Page_66" id="Page_66">[Pg 66]</a></span> +milk glands, which are absolutely peculiar to +the Mammalia, are still in a very primitive +stage, and do not yet produce milk proper; +and there is only a temporary shallow marsupium.</p> + +<p>19. Stage of <i>Metatheria</i>, or <i>Marsupialia</i>, +are direct descendants of Prototheria; but +they show higher development by the reduction +of the coracoid bones and the interclavicle. +The original cloaca is divided into +a rectal chamber and a uro-genital sinus, completely +separated, at least in the males; they +are viviparous; the young are received into +a permanent marsupium, in the walls of which +are formed typical milk glands and nipples, +but the embryo is still devoid of a placenta, +although some recent marsupials show indications +of such an organ. The corpus callosum +in the brain is still very weak.</p> + +<p>Most of the marsupials are extinct. They +occur from the Upper Trias onwards, and +had in the Jurassic epoch attained a wide +distribution both in Europe and in America.<span class="pagenum"><a name="Page_67" id="Page_67">[Pg 67]</a></span> +Since the Tertiary epoch they have been +restricted to America and to the Australian +region, and are now represented by about 150 +species.</p> + +<p>20. Stage of <i>Prochoriata</i>, or early <i>Placentalia</i>: +a further development of the Metatheria +by the development of a placenta, loss +of the marsupium and the marsupial bones, +complete division by the perineum of the +anal and uro-genital chambers, stronger +development of the corpus callosum, or chief +commissure of the two hemispheres of the +brain.</p> + +<p>Placentalia must have come into existence +during the Cretaceous epoch. Up to that +time all the Mammalia seem to have +belonged to either Prototheria or to Metatheria; +but in the early Eocene we can +distinguish the main groups of Placentalia—namely, +(1) Trogontia, now represented by +the rodents; (2) Edentata, or sloths, armadilloes, +etc.; (3) Carnassia, or Insectivora +and Carnivora; (4) Chiroptera, or bats;<span class="pagenum"><a name="Page_68" id="Page_68">[Pg 68]</a></span> +(5) Cetomorpha, or whales and dugongs; +(6) Ungulata; (7) Primates. Of these +groups, the first and second, third and fourth, +fifth and sixth, can perhaps, to judge from +palæontological evidence, be combined into +three greater groups, as indicated by the +fossil Esthonychida, Ictopsida, and Condylarthra, +in addition to the ancestral Primates, +or Lemuravida, as the fourth large branch of +the ancestral-tree where this has reached the +placental level. Among none of the first +three branches can we look for the ancestors +of the Primates. The Lemuravida, therefore, +represent a branch equivalent to the three +other branches.</p> + +<p>21. Stage of <i>Lemures</i>, or <i>Prosimiæ</i>, comprising +the older members of the Primates, +consequently approaching most nearly to the +Lemuravida. The limbs are modified into +pentadactyle hands and feet of the arboreal +type, and are protected by nails. The dentition +is of the frugivorous or omnivorous type, +with an originally complete series of teeth,</p> + +<p><span class="pagenum"><a name="Page_69" id="Page_69">[Pg 69]</a></span></p> + +<p><span class="pagenum"><a name="Page_70" id="Page_70">[Pg 70]</a></span></p> + +<p>with milk teeth and with permanent. The +orbit is surrounded by a complete bony ring, +posteriorly by a fronto-jugal arch, but still +widely communicating with the temporal +fossa. The placenta is diffuse and non-deciduous.</p> +<p class= "center"> +ANCESTRAL TREE OF THE MAMMALIA.<br /> + +<i>'Systematische Phylogenie,' § 386.</i></p> + +<table id="atm" summary="mammalia" cellspacing="0"> +<tr> + <td class="tdc"></td> + <td class="tdc"><i><small>Perissodactyla</small></i></td> + <td class="tdc" ></td> + <td class="tdc" ><i>Homo</i></td> + <td class="tdc" ></td> + <td class="tdc" ><small><i>Carnivora</i></small></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl"><i><small>Artiodactyla</small></i></td> + <td class="tdc">|</td> + <td class="tdc">(<i><small>Litopterna</small></i>)</td> + <td class="tdc">|</td> + <td class="tdc"></td> + <td class="tdc"> |</td> + <td class="tdc"><small><i>Pinnipedia</i></small></td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdc"><i><small>Anthropoidae</small></i></td> + <td class="tdc"></td> + <td class="tdr">|——</td> + <td class="tdl"> ——'</td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdr">| —— </td> + <td class="tdl"> —— '</td> + <td class="tdc">|</td> + <td class="tdc"></td> + <td class="tdc">|</td> + <td class="tdc"></td> +</tr> +<tr> + <td class="tdr">'——</td> + <td class="tdl"> ——|</td> + <td class="tdc"></td> + <td class="tdc"><i><small>Catarhinæ</small></i></td> + <td class="tdc"></td> + <td class="tdc"><small><i>Carnassia</i></small></td> + <td class="tdc"></td> +</tr> +<tr> + <td class="tdc"></td> + <td class="tdr">'—— </td> + <td class="tdl"> —— ,</td> + <td class="tdc">|</td> + <td class="tdc"></td> + <td class="tdc">|</td> + <td class="tdc"><i><small>Chiroptera</small></i></td> +</tr> +<tr> + <td class="tdc"><small>(<i>Amblypoda</i>)</small></td> + <td class="tdc"><i><small>Proboscidea</small></i></td> + <td class="tdc">|</td> + <td class="tdc"><i><small>Platyrhinæ</small></i></td> + <td class="tdc"><i><small>Insectivora</small></i></td> + <td class="tdc">|</td> + <td class="tdc">|</td> +</tr> +<tr> + <td class="tdr">'——</td> + <td class="tdl">——|</td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdr">|——</td> + <td class="tdl"> ——'</td> + <td class="tdc">|</td> +</tr> +<tr> + <td class="tdc"></td> + <td class="tdr">' —— </td> + <td class="tdl"> —— |</td> + <td class="tdc"><i><small>Simiæ</small></i></td> + <td class="tdc">|</td> + <td class="tdc"></td> + <td class="tdc">|</td> +</tr> +<tr> + <td class="tdc"><small><i>Cetacea</i></small></td> + <td class="tdc"><i><small>Sirenia</small></i></td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdr">|——</td> + <td class="tdc">————</td> + <td class="tdl">——'</td> +</tr> +<tr> + <td class="tdr">|—— </td> + <td class="tdl">——'</td> + <td class="tdc">|</td> + <td class="tdc"><i><small>Lemures</small></i></td> + <td class="tdc">|</td> + <td class="tdc"><i><small>Rodentia</small></i></td> + <td class="tdl"></td> +</tr> +<tr> + <td class="tdc"><i><small>Cetomorpha</small></i></td> + <td class="tdc"></td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdl"></td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdc"><i><small>Hyracoidea</small></i></td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdr"><i><span class="u"><small>Ictopsales</small></span></i></td> + <td class="tdc">(<i><small>Tillodontia</small></i>)</td> + <td class="tdl"></td> +</tr> +<tr> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdc"><i><span class="u"><small>Lemuravidæ</small></span></i></td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdc"></td> +</tr> +<tr> + <td class="tdr">'——</td> + <td class="tdc">——'——</td> + <td class="tdl"> —— |</td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdc"><i><small>Trogontia</small></i></td> + <td class="tdc"><i><small>Edentata</small></i></td> +</tr> +<tr> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc"><i><span class="u"><small>Condylarthrales</small></span></i></td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdr">|——</td> + <td class="tdl"> ——'</td> +</tr> +<tr> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdc">|</td> + <td class="tdc"><i><span class="u"><small>Esthonychales</small></span></i></td> + <td class="tdc"></td> +</tr> +<tr> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdr">' —— </td> + <td class="tdr">——|——</td> + <td class="tdc">——'——</td> + <td class="tdl">——'</td> + <td class="tdc"></td> +</tr> +<tr> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc">|</td> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc"></td> +</tr> +<tr> + <td class="tdc" colspan="7">Eutheria s. Placentalia</td> + </tr> +<tr> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc">|</td> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc"></td> +</tr> +<tr> + <td class="tdc" colspan="3"><i><small>Marsupialia diprotodontia</small></i></td> + <td class="tdc">|</td> + <td class="tdc" colspan="3"><i><small>Marsupialia polyprotodontia</small></i></td> +</tr> +<tr> + <td class="tdc"></td> + <td class="tdr">'——</td> + <td class="tdc">————</td> + <td class="tdc">——|——</td> + <td class="tdc">————</td> + <td class="tdl">——'</td> + <td class="tdc"></td> +</tr> +<tr> + <td class="tdc" colspan="7">Metatheria</td> +</tr> +<tr> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc">|</td> + <td class="tdc"><i><small>Monotremata</small></i></td> + <td class="tdc"></td> + <td class="tdc"><small>(<i>Allotheria</i>)</small></td> +</tr> +<tr> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc">Prototheria</td> + <td class="tdc">|</td> + <td class="tdc"></td> + <td class="tdc">|</td> +</tr> +<tr> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdc"></td> + <td class="tdr">|——</td> + <td class="tdl">——'——</td> + <td class="tdc">————</td> + <td class="tdl">——'</td> +</tr> +<tr> + <td class="tdc" colspan ="7"><i><span class="u"><small>Hypotheria s. Promammalia</small></span></i></td> +</tr> +</table> +<p> +<i>Names in brackets indicate extinct groups.<br /> +Names <span class="u">underlined</span> indicate hypothetical groups or combinations.</i><br /> +</p> + +<p>22. Stage of <i>Simiæ</i>. Orbit completely +separated from the temporal fossa by an +inward extension of the frontal and malar +bones meeting the alisphenoid. Placenta consolidated +into a disc, and with a maternal +deciduous portion. Mammæ pectoral only. +The dental formula is 2.1.3.3. All the +fingers and toes are protected by flat nails. +The tail is long. The American prehensile-tailed +monkeys are a lower side-branch.</p> + +<p>23. Stage of <i>Catarrhinæ Cercopithecidæ</i>. +The dental formula is 2.1.2.3, owing to the +loss of one pair of premolars in each jaw. +The frontal and alisphenoid bones are in +contact, separating the parietal from the +malar bone; this feature is correlated with +the enlarged brain. The internarial septum<span class="pagenum"><a name="Page_71" id="Page_71">[Pg 71]</a></span> +is narrow, and the nostrils look forwards and +downwards instead of sidewards—hence the +term 'Catarrhinæ.' The external auditory +meatus is long and bony. The tail is long, +with the exception of <i>Macacus inuus</i>. The +body is covered with a thick coat of furry +hair. Catarrhine monkeys have existed, we +know with certainty, since the Miocene.</p> + +<p>24. Stage of <i>Catarrhinæ Anthropoidæ</i>, or +<i>Apes</i>. Now represented by the large apes—namely, +the Hylobates or gibbon of South-Eastern +Asia, <i>Simia satyrus</i>, the orang-utan +of Sumatra and Borneo, <i>Troglodytes gorilla</i>, +<i>T. niger</i> and <i>T. calvus</i>, the gorilla and the +chimpanzees from Western Equatorial Africa. +Of fossils are to be mentioned Pliopithecus +and Dryopithecus from European Miocene, +and <i>Troglodytes sivalensis</i> from the Pliocene +of the Punjaub. The tail is reduced to a +few caudal vertebræ, which are transformed +into a coccyx, not visible externally; but in +the embryos of apes and man the tail is still +a conspicuous feature. The walk is semi<span class="pagenum"><a name="Page_72" id="Page_72">[Pg 72]</a></span>erect; +in adaptation to the prevailing arboreal +life, the arms are longer than the legs. +The hair of the body is considerably more +scanty than in the tailed monkeys. <i>Troglodytes +calvus</i>, a species or variety of chimpanzee, +is bald-headed. None of the recent +genera of apes can lay claim to a place in +the ancestry of mankind.</p> + +<p>25. Stage of <i>Pithecanthropi</i>. Hitherto the +only known representative is <i>Pithecanthropus +erectus</i>, from the Upper Pliocene of Java. In +adaptation to a more erect gait, the legs have +become stronger and the hind-hand has been +turned into a flat-soled walking 'foot.' The +brain is considerably enlarged. Presumably +it is still devoid of so-called articulate speech; +this is indicated by the fact that children +have to learn the language of their parents, +and by the circumstance that comparative +philology declares it impossible to reduce the +chief human languages to anything like one +common origin.</p> + +<p>26. <i>Man.</i> Known with certainty to have<span class="pagenum"><a name="Page_73" id="Page_73">[Pg 73]</a></span> +existed as an implement-using creature in the +last Glacial epoch. His probable origin +cannot, therefore, have been later than the +beginning of the Plistocene. The place of +origin was probably somewhere in Southern +Asia.</p> + +<p>Whilst we have to admit that there are +great defects in the older (invertebrate) +portion of our pedigree, we have all the more +reason to be satisfied with the positive results +of our investigation of the more recent (vertebrate) +part of it. All modern researches have +confirmed the views of Lamarck, Darwin, and +Huxley, and they allow of no doubt that the +nearest vertebrate ancestors of mankind were +a series of Tertiary Primates.</p> + +<p>Particularly valuable are the admirable +attempts of the two zoologists, Paul and Fritz +Sarasin,<a name="FNanchor_23_23" id="FNanchor_23_23"></a><a href="#Footnote_23_23" class="fnanchor">[23]</a> to throw light upon the human +phylogeny by painstaking comparison of all +the skeletal parts of man with those of the<span class="pagenum"><a name="Page_74" id="Page_74">[Pg 74]</a></span> +anthropoid apes. They have shown that +among the lower races of man the primitive +Veddahs of Ceylon approach the apes most +nearly, and that among the latter the chimpanzee +stands nearest to man.</p> + +<p>The direct descent of man from some +extinct ape-like form is now beyond doubt, +and admits of being traced much more clearly +than the origin of many another mammalian +order. The pedigrees of the Elephants, +the Sirenia, the Cetacea, and, above all, of +the Edentata, for example, are much more +obscure and difficult to explain. In many +parts of their organization—for example, in +the number and structure of his five digits and +toes—man and monkeys have remained much +more primitive than most of the Ungulata.</p> + +<p>The immense significance of this positive +knowledge of the origin of man from some +Primate does not require to be enforced. Its +bearing upon the highest questions of philosophy +cannot be exaggerated. Among modern +philosophers no one has perceived this more<span class="pagenum"><a name="Page_75" id="Page_75">[Pg 75]</a></span> +deeply than Herbert Spencer.<a name="FNanchor_24_24" id="FNanchor_24_24"></a><a href="#Footnote_24_24" class="fnanchor">[24]</a> He is one of +those older thinkers who before Darwin were +convinced that the theory of development +is the only way to solve the 'enigma of the +world.' Spencer is also the champion of those +evolutionists who lay the greatest weight +upon <i>progressive heredity</i>, or the much combated +<i>heredity of acquired characters</i>. From +the first he has severely attacked and criticised +the theories of Weismann, who denies +this most important factor of phylogeny, and +would explain the whole of transformism by +the 'all-sufficiency of selection.' In England +the theories of Weismann were received with +enthusiastic acclamation, much more so than +on the Continent, and they were called 'Neo-Darwinism,' +in opposition to the older conception +of Evolution, or 'Neo-Lamarckism.' +Neither of those expressions is correct. +Darwin himself was convinced of the fundamental +importance of progressive heredity<span class="pagenum"><a name="Page_76" id="Page_76">[Pg 76]</a></span> +quite as much as his great predecessor +Lamarck; as were also Huxley and Spencer.</p> + +<p>Three times I had the good fortune to +visit Darwin at Down, and on each occasion +we discussed this fundamental question in +complete harmony. I agree with Spencer +in the conviction that progressive heredity is +an indispensable factor in every true monistic +theory of Evolution, and that it is one of its +most important elements. If one denies +with Weismann the heredity of acquired +characters, then it becomes necessary to have +recourse to purely mystical qualities of germ-plasm. +I am of the opinion of Spencer, that +in that case it would be better to accept a +mysterious creation of all the various species +as described in the Mosaic account.</p> + +<p>If we look at the results of modern anthropogeny +from the highest point of view, and +compare all its empirical arguments, we are +justified in affirming that <i>the descent of man +from an extinct Tertiary series of Primates +is not a vague hypothesis, but an historical fact</i>.</p> + +<p><span class="pagenum"><a name="Page_77" id="Page_77">[Pg 77]</a></span></p> + +<p>Of course, this fact cannot be proved +<i>exactly</i>. We cannot explain all the innumerable +physical and chemical processes, +all the physiological mutations, which have +led during untold millions of years from the +simplest Monera and from the unicellular +Protista upwards to the chimpanzee and to +man. But the same consideration applies to +all historical facts. We all believe that +Aristotle, Cæsar, and King Alfred did live; +but it is impossible to give a proof within +the meaning of modern exact science. We +believe firmly in the former existence of +these and other great heroes of thought, +because we know well the works they have +left behind them, and we see their effects in +the history of human culture. These indirect +arguments do not furnish stronger evidence +than those of our history as vertebrates. +We know of many Jurassic mammals only +a single bone, the under jaw. We all +believe that these mammals possessed also +an upper jaw, a skull, and other bones. But<span class="pagenum"><a name="Page_78" id="Page_78">[Pg 78]</a></span> +the so-called 'exact school,' which regards +the transformation of species as a hypothesis +not proven, must suppose that the +mandibula was the only bone in the body of +these curious animals.</p> + +<p>Looking forward to the twentieth century, +I am convinced that it will universally accept +our theory of descent, and that future science +will regard it as the greatest advance made +in our time. I have no doubt that the +influence of the study of anthropogeny upon +all other branches of science will be fruitful +and auspicious. The work done in the +present century by Lamarck and Darwin +will in all future times be considered one +of the greatest conquests made by thinking +man.</p> + +<p><span class="pagenum"><a name="Page_79" id="Page_79">[Pg 79]</a></span></p> + +<p class="center">EVOLUTIONARY STAGES OF THE PRINCIPAL +GROUPS OF VERTEBRATA.<a name="FNanchor_25_25" id="FNanchor_25_25"></a><a href="#Footnote_25_25" class="fnanchor">[25]</a> </p> +<table id="esv" summary="stages"> +<tr> + <td class="tdc"><small>STAGES OF THE</small></td> + <td class="tdc"><small> CLASSES.</small></td> + <td class="tdc"><small>STAGES OF THE HEART.</small></td> +</tr> +<tr> + <td class="tdc"><small>PAIRED LIMBS.</small></td> + <td class="tdc"></td> + <td class="tdc"></td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">{1. <i>Acrania.</i></td> + <td class="tdl">I. <i>Leptocardia.</i></td> +</tr> +<tr> + <td class="tdl">I. <i>Adactylia</i></td> + <td class="tdl">{</td> + <td class="tdl"> Cold-blooded; heart</td> +</tr> +<tr> + <td class="tdl"> s. <i>Impinnata</i>.</td> + <td class="tdl">{</td> + <td class="tdl"> with one chamber;</td> +</tr> +<tr> + <td class="tdl"> Without jaws</td> + <td class="tdl">{</td> + <td class="tdl"> without lungs.</td> +</tr> +<tr> + <td class="tdl"> and limbs.</td> + <td class="tdl">{</td> + <td class="tdl"></td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">{2. <i>Cyclostomata.</i></td> + <td class="tdl">}II. <i>Ichthyocardia.</i></td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl"></td> + <td class="tdl">} Cold-blooded; heart</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl"></td> + <td class="tdl">} two-chambered, with</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl"></td> + <td class="tdl">} one atrium and one</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl"></td> + <td class="tdl">} ventricle; heart</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl"></td> + <td class="tdl">} containing venous</td> +</tr> +<tr> + <td class="tdl">II. <i>Polydactylia</i></td> + <td class="tdl">{3. <i>Pisces.</i></td> + <td class="tdl">} blood only; without lungs</td> +</tr> +<tr> + <td class="tdl"> s. <i>Pinnata</i>.</td> + <td class="tdl">{</td> + <td class="tdl"></td> +</tr> +<tr> + <td class="tdl"> With two</td> + <td class="tdl">{</td> + <td class="tdl"></td> +</tr> +<tr> + <td class="tdl"> pairs of fins.</td> + <td class="tdl">{ 4. <i>Dipnoi.</i></td> + <td class="tdl">}III. <i>Amphicardia.</i></td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl"></td> + <td class="tdl"> }Cold-blooded; heart</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl"></td> + <td class="tdl">} with three complete</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl"></td> + <td class="tdl">} chambers, namely, with</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl"></td> + <td class="tdl">} two atria and one</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">{ 5. <i>Amphibia.</i></td> + <td class="tdl">} ventricle, or (Reptilia)</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">{</td> + <td class="tdl">} two ventricles with still</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">{</td> + <td class="tdl">} incomplete septum; heart</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">{</td> + <td class="tdl">} containing mixed venous</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">{</td> + <td class="tdl">} and arterialized</td> +</tr> +<tr> + <td class="tdl">III. <i>Pentadactylia</i></td> + <td class="tdl">{ 6. <i>Reptilia.</i></td> + <td class="tdl">} blood; with lungs.</td> +</tr> +<tr> + <td class="tdl"> s. <i>Tetrapoda</i>.</td> + <td class="tdl">{</td> + <td class="tdl"></td> +</tr> +<tr> + <td class="tdl"> With two</td> + <td class="tdl">{</td> + <td class="tdl">{IV. <i>Thermocardia.</i></td> +</tr> +<tr> + <td class="tdl"> pairs of</td> + <td class="tdl">{</td> + <td class="tdl">{ Warm-blooded; heart</td> +</tr> +<tr> + <td class="tdl"> pentadactyle</td> + <td class="tdl">{</td> + <td class="tdl">{ with four complete</td> +</tr> +<tr> + <td class="tdl"> limbs (unless</td> + <td class="tdl">{7. <i>Aves.</i></td> + <td class="tdl">{ chambers, namely, two</td> +</tr> +<tr> + <td class="tdl"> they have</td> + <td class="tdl">{</td> + <td class="tdl">{ auricles and two</td> +</tr> +<tr> + <td class="tdl"> been lost by</td> + <td class="tdl">{</td> + <td class="tdl">{ ventricles; right half</td> +</tr> +<tr> + <td class="tdl"> reduction).</td> + <td class="tdl">{</td> + <td class="tdl">{ of the heart with venous,</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">{</td> + <td class="tdl">{ left half with arterialized,</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">{8. <i>Mammalia.</i></td> + <td class="tdl">{ blood; with lungs.</td> +</tr> +</table> + + +<p><span class="pagenum"><a name="Page_80" id="Page_80">[Pg 80]</a></span></p> + +<hr class="chap"/> +<div class="chapter-beginning"/> +<h2>BIOGRAPHICAL SKETCHES</h2> + + +<p><span class="smcap"><a name="Footnote_40" id="Footnote_40"></a><a href="#FNanchor_40">Jean Baptiste de Monet</a>, Chevalier de +<a name="Footnote_44" id="Footnote_44"></a><a href="#FNanchor_44">Lamarck</a></span>, was born on August 1, 1744, in +Picardy, where his father owned land. +Originally educated for the Church, he +soon enlisted, and distinguished himself in +active service. Owing to an accident affecting +his health, the young Lieutenant gave +up the military career, and, without means, +studied medicine and natural sciences at +Paris. In 1778 appeared his 'Flore française.' +In 1793 he was appointed to a +Chair of Zoology at the newly-formed Musée +d'Histoire Naturelle. He had the misfortune +to become gradually blind, and the last years +of his life were spent amid straitened circumstances. +He died in 1829.</p> + +<p><span class="pagenum"><a name="Page_81" id="Page_81">[Pg 81]</a></span></p> + +<p>In 1794 Lamarck divided the whole animal +kingdom into vertebrate and invertebrate +animals, and founded successively the groups +of Crustacea, Arachnida, Annelida, and +Radiata. Between 1816 and 1822 he published +his celebrated 'Histoire naturelle des +Animaux sans Vertèbres.'</p> + +<p>His most famous work is the 'Philosophie +zoologique,' 1809.</p> + +<p>Assuming the spontaneous origin of life, +he propounded the doctrine that all animals +and plants have arisen from low forms +through incessant modifications and changes. +In this respect he was in absolute opposition +to Cuvier, who upheld the immutability of +species, and did his best by absolute silence +to suppress the spread of the new doctrine.</p> + +<p>Lamarck has explained his views of transformism +chiefly in the seventh chapter of the +first volume of his 'Philosophie zoologique.'</p> + +<p>Organisms strive to accommodate or adapt +themselves to new circumstances, or to satisfy +new requirements—<i>e.g.</i>, climate, mode of<span class="pagenum"><a name="Page_82" id="Page_82">[Pg 82]</a></span> +procuring food, escape from enemies. The +continued function of parts of an organism +changes the old and produces new organs. +The acquirements are inherited by the offspring, +and thus are produced the more complicated +from simpler organisms. Continued +disuse brings about degeneration and ultimate +loss of an organ.</p> + +<p>Lamarck consequently sees in the adaptability, +or power of adaptation, which he +assumes for all living matter the ultimate +cause of variation; and, as he was certainly +the first to point out that acquired characters +are inherited by the progeny, he has given +a working explanation of Evolution.</p> + +<p>But his doctrine did not spread—partly +because he was misunderstood. His theory, +that a new want, by making itself felt, exacts +from the animal new exertions, perhaps from +parts hitherto not used, until the want is +satisfied—this way of putting it sounds too +teleological to explain the yearned-for change +in a mechanical or natural way. Moreover,<span class="pagenum"><a name="Page_83" id="Page_83">[Pg 83]</a></span> +many of his examples lacked the exact basis +of experiment and observation necessary for +their acceptance. Witness that of the neck of +the giraffe,—a never-failing source of ridicule +to men who cannot see the deeper purpose +underlying the well-meant attempt at an explanation, +which failed from want of complete +knowledge of the intricate circumstances.</p> + +<p>However, the theory of transformism was, +so to speak, in the air; and various authors +have written on the subject, filling the gap +between Lamarck and Darwin, especially +Goethe, Treviranus, Leopold von Buch, +and Herbert Spencer. But it is Darwin's +immortal merit to have opened our eyes by +his theory of natural selection, which is, at +least, the first attempt to explain some of the +causes and incidents of organic Evolution +in a natural mechanical way. Moreover, he +was the first clearly to express the fundamental +principles of the theory of descent, to +elaborate what had been at best a general +sketch of an ill-defined problem, and to enter<span class="pagenum"><a name="Page_84" id="Page_84">[Pg 84]</a></span> +into detail, supported by a host of painstaking +observations, the making of which had +taken him half a lifetime. Darwin, without +going further than cursorily into the causes +of variation, argued as follows: We know +that variations do occur in every kind of +living creatures. Some of these variations +lead to something, while others do not. An +enormously greater number of animals and +plants are born than reach maturity and can +in their turn continue the race. What is the +regulating factor? His answer is, The +struggle for existence—in other words, the +weeding out of the less fit, or rather of the +owners of those variations which are not so +well adapted to their surroundings.</p> + +<p>For 'adapted' we had better read 'adaptable,' +because a variation which does not +answer, which cannot be made use of, or, +still more notably, is a hindrance or disadvantage, +does not become an adapted +feature. There is often a confusion between +adaptation as an accomplished fact, a feature,<span class="pagenum"><a name="Page_85" id="Page_85">[Pg 85]</a></span> +or resultant condition, and adaptation as the +mode of fitting the organism to, or making +the best of, the prevailing surroundings or +circumstances.</p> + + +<p><span class="smcap">Étienne Geoffroy Saint-Hilaire</span> was +born in 1772 at Étampes, Seine-et-Oise. +He was originally brought up for the Church; +but when already ordained he attended +lectures on natural science and medicine in +Paris. He managed to get the place of +assistant in the Musée d'Histoire Naturelle; +he became Professor of Zoology in 1793, and +took the opportunity of encouraging young +Cuvier. Later he became Professor of +Zoology of the Faculté des Sciences, and in +1818 he published his remarkable 'Philosophie +anatomique.' He died in 1844.</p> + +<p>He had conceived the 'unity of organic +composition,' meaning that there is only one +plan of construction,—the same principle, but +varied in its accessory parts. In 1830, when +Geoffroy proceeded to apply to the Inverte<span class="pagenum"><a name="Page_86" id="Page_86">[Pg 86]</a></span>brata +his views as to the uniformity of +animal composition, he found a vigorous +opponent in Cuvier. Geoffroy, like Goethe, +held that there is in Nature a law of compensation, +or balancing of growth, so that if +one organ take on an excess of development, +it is at the expense of another part; and he +maintained that, since Nature takes no +sudden leaps, even organs which are superfluous +in any given species, if they have +played an important part in other species of +the same family, are retained as rudiments, +which testify to the permanence of the +general plan of creation. It was his conviction +that, owing to the conditions of life, +the same forms had <i>not</i> been perpetuated +since the origin of all things, although it was +not his belief that existing species were becoming +modified. Cuvier, on the other +hand, maintained the absolute invariability +of species, which, he declared, had been +created with regard to the circumstances in +which they were placed, each organ con<span class="pagenum"><a name="Page_87" id="Page_87">[Pg 87]</a></span>trived +with a view to the function it had to +fulfil,—thus putting the effect for the cause +('Encyclopædia Britannica,' 9th edition, +vol. xxi., p. 171).</p> + + +<p><span class="smcap">George <a name="Footnote_46" id="Footnote_46"></a><a href="#FNanchor_46">Cuvier</a></span> +in the department of Doubs, which +at that time belonged to Württemberg. He +was educated at Stuttgart, and studied +political economy. While acting as private +tutor to a French family in France he +followed his favourite pursuit, the study of +natural sciences. Geoffroy Saint-Hilaire +heard of him, and appointed him assistant in +the department of comparative anatomy in the +Musée d'Histoire Naturelle. In 1799 he was +elected Professor of Natural History at the +Collège de France, and soon after he became +Perpetual Secretary of the Institut National. +In 1831, a year before his death, Louis +Philippe raised him to the rank of a peer of +France.</p> + +<p>Cuvier was the first to indicate the true<span class="pagenum"><a name="Page_88" id="Page_88">[Pg 88]</a></span> +principle upon which the natural classification +of animals should be based—namely, +their structure. It is the study of the +anatomy of the creatures and their comparison +which affords the only sound basis +of a classification. The work which had the +greatest influence upon the scientific public +is his 'Règne animal distribué d'après son +Organisation,' 1817. The system which he +propounded in this book gradually came to +have almost world-wide fame, and, in spite +of its many obvious deficiencies, still lingers +in some of our most recent text-books.</p> + +<p>A standard work is his 'Leçons d'Anatomie +comparée,' and, in truth, he is the founder +of that kind of comparative anatomy which +was brought to such a high state by his +pupil, the late Sir Richard Owen. Cuvier +discovered the law of 'correlation of growth,' +and was the first to apply this law to the +reconstruction of animals from fragments: +see his monumental work entitled 'Recherches +sur les Ossemens fossiles,' 1812.</p> + +<p><span class="pagenum"><a name="Page_89" id="Page_89">[Pg 89]</a></span></p> + +<p>Cuvier, however, as a strict matter-of-fact +man, was incapable of appreciating the speculative +conclusions which were drawn by his +contemporaries Saint-Hilaire and Lamarck. +On the contrary, he firmly stuck to the +doctrine of the immutability of species; and, +in order to account for the existence of +animals whose kind exists no longer, he invented +the famous doctrine of successive +cataclysms.</p> + + +<p><span class="smcap">Karl Ernst <a name="Footnote_41" id="Footnote_41"></a><a href="#FNanchor_41">von Baer</a></span> +was born in 1792 +in Esthonia, studied at Dorpat and then at +Würzburg, where Döllinger introduced him +to comparative anatomy. For a few years +he was a <i>Privat-docent</i> at Berlin; then he +went to Königsberg as Professor of Zoology +and Embryology. In 1834 he became an +Academician at St. Petersburg, where for +many years he was occupied with the most +varied studies, chiefly geographical and +ethnological. The last years of his long, +active life he spent in contemplative retire<span class="pagenum"><a name="Page_90" id="Page_90">[Pg 90]</a></span>ment +on his paternal estate, and he died at +Dorpat in 1876.</p> + +<p>While still at Würzburg he induced his +friend Pander, a young man of means, to study +the development of the chick; and Pander was +the first to start the theory of the germinal +layers from which all the organs arise. +Baer, however, continued these researches in +Königsberg, and after nine years' labour produced +his epoch-making work, 'Ueber Entwicklungsgeschichte +der Thiere: Beobachtung +und Reflexion,' Königsberg, 1828. Nine +years later he completed the second volume. +He established upon a firm basis the theory +of the germinal layers, and by further 'reflexions' +arrived at the elucidation of some of +the most fundamental laws of biology. For +example, in the first volume he made the +following prophetic statement: 'Perhaps all +animals are alike, and nothing but hollow +globes at their earliest developmental beginning. +The farther back we trace their +development, the more resemblance we find<span class="pagenum"><a name="Page_91" id="Page_91">[Pg 91]</a></span> +in the most different creatures. And this +leads to the question whether at the beginning +of their development all animals are essentially +alike, and referable to one common ancestral +form. Considering that the "germ" (which +at a certain stage appears in the shape of a +hollow globe or bag) is the undeveloped animal +itself, we are not without reason for assuming +that the common fundamental form is that of a +simple vesicle, from which every animal is +evolved, not only theoretically, but historically.'</p> + +<p>This statement is all the more wonderful +when we consider that the cells, the all-composing +individual units, were not discovered +until ten years later.</p> + +<p>In 1829 Baer discovered the human egg, +and later the chorda dorsalis. In an address +delivered in 1834, entitled 'The Most Universal +Law of Nature in all Development,' he +explained that only from a most superficial +point of view can the various species be looked +upon as permanent and immutable types;<span class="pagenum"><a name="Page_92" id="Page_92">[Pg 92]</a></span> +that, on the contrary, they can be nothing +but passing stages, or series of stages, of +development, which have been evolved by +transformation out of common ancestral forms.</p> + + +<p><span class="smcap">Johannes Mueller</span>, born at Coblenz in +1801, established himself as <i>Privat-docent</i> at +Bonn, where in 1830 he became Professor of +Physiology. In 1833 he accepted the Chair +of Anatomy and Physiology at Berlin, where +he died in 1858.</p> + +<p>He was one of the most distinguished +physiologists and comparative anatomists. +By summarizing the labours and discoveries +already made in the field of physiology, by +reducing them to order, and abstracting the +general principles, he became the founder of +modern physiology. But he was scarcely +less distinguished by his researches in +comparative anatomy. His 'Vergleichende +Anatomie der Myxinoiden,' in <i>Abhandlungen +der Berliner Akademie</i>, 1835-45, and 'Ueber +die Grenzen der Ganoiden' (<i>ibid.</i>, 1846), are +standard works of lasting value.</p> + +<p><span class="pagenum"><a name="Page_93" id="Page_93">[Pg 93]</a></span></p> + +<p>Mueller exercised a stimulative influence +as a teacher. Many well-known men—such +as Helmholtz, Gegenbaur, Bruecke the physiologist, +Guenther the zoologist, Virchow the +pathologist, Koelliker and Haeckel—have +been his pupils.</p> + + +<p><span class="smcap">Rudolph <a name="Footnote_45" id="Footnote_45"></a><a href="#FNanchor_45">Virchow</a></span> +Schievelbein, a small town in Eastern +Pomerania. He studied medicine in Berlin +as a pupil of Johannes Mueller, and went +in 1849 to Würzburg, where, under the +influence of Koelliker, and Leydig the pathologist, +he laid the foundation of an entirely +new branch of medical science—that of +'cellular pathology.' Since 1856 he has +filled the principal Chair of Pathology at +Berlin. In 1892 he received the Copley +medal of the Royal Society.</p> + +<p>'His contributions to the study of morbid +anatomy have thrown light upon the diseases +of every part of the body; but the broad +and philosophical view he has taken of the<span class="pagenum"><a name="Page_94" id="Page_94">[Pg 94]</a></span> +processes of pathology has done more than +his most brilliant observations to make the +science of disease.</p> + +<p>'In pathology, strictly so called, his two +great achievements—the detection of the +cellular activity which lies at the bottom of +all morbid as well as normal physiological +processes, and the classification of the important +group of new growths on a natural +histological basis—have each of them not +only made an epoch in medicine, but have +also been the occasion of fresh extension of +science by other labourers' (Proc. Royal +Soc., 1892).</p> + +<p>Virchow has not confined himself to +medicine. He takes the keenest interest in +anthropology and ethnology, on which subjects +he has contributed many papers. +Together with his colleagues Helmholtz the +physicist, and Du Bois Reymond the physiologist, +he has taken a leading place in the +spreading of natural science; but, unfortunately, +he did not take to the doctrine of<span class="pagenum"><a name="Page_95" id="Page_95">[Pg 95]</a></span> +Evolution, and for the last thirty years has +been its declared antagonist, rarely missing +an opportunity of denouncing everything but +descriptive anatomy and zoology as the +unsound speculations of dreamers. This has +on more than one occasion brought him into +sharp conflict with Haeckel. His activity is +astonishing, especially if it be remembered that +Virchow has for many years been one of the +most conspicuous leaders of the Progressists +and Radicals in the German Parliament and +Berlin town-council.</p> + + +<p><span class="smcap">Edward Drinker Cope</span> was born at +Philadelphia, Pa. After studying at several +Continental Universities, especially at Heidelberg, +he became first Professor of Natural +Science at Haverford College, and later +Professor of Geology and Mineralogy. He +died at an early age in 1897. As a member +of various geological expeditions and other +surveys, he explored chiefly Kansas, Wyoming, +and Colorado; and he published many<span class="pagenum"><a name="Page_96" id="Page_96">[Pg 96]</a></span> +most suggestive papers on the fossil vertebrate +fauna of North America, and on classification +especially of Amphibia and Reptiles.</p> + +<p>Among works of a more general philosophical +scope may be mentioned 'The +Origin of the Fittest,' 1887, and his latest +work, 'The Primary Factors of Organic +Evolution,' 1896.</p> + + +<p><span class="smcap">Albert von <a name="Footnote_50" id="Footnote_50"></a><a href="#FNanchor_50">Koelliker</a></span> +became Professor of Anatomy at Würzburg. +His earlier studies and discoveries contributed +considerably to the systematic development +of the cell theory. In 1844 he observed the +division and further multiplication of the +original egg cell. Next year he showed the +continuity between nerve cells and nerve +fibres in the Vertebrata; later, that the non-striped +or smooth muscular tissue is composed +of cellular elements. He demonstrated that +the Gregarinæ are unicellular creatures. In +1852 he went with his younger friend Gegenbaur +to Messina, where he studied especially<span class="pagenum"><a name="Page_97" id="Page_97">[Pg 97]</a></span> +the development of the Cephalopoda (cuttlefishes +and allies); and he produced a magnificent +work on Alcyonaria, Medusæ, and +other allied forms. He elucidated the development +of the vertebral column, especially +with reference to the notochord.</p> + +<p>In 1848 he founded, together with Th. von +Siebold, the famous <i>Zeitschrift für wissenschaftliche +Zoologie</i>.</p> + +<p>A standard work on mammalian embryology +is his 'Entwicklungsgeschichte +des Menschen und der höheren Thiere,' a +text-book of which the second edition +appeared in 1879.</p> + +<p>At the anniversary meeting of 1897 he +received the Copley medal, the highest honour +which the Royal Society can bestow.</p> + + +<p><span class="smcap">Carl <a name="Footnote_49" id="Footnote_49"></a><a href="#FNanchor_49">Gegenbaur</a> +</span> was born on August 21, +1826, in Bavaria. He studied medicine and +kindred subjects in Würzburg, and as a pupil +of Johannes Mueller in Berlin.</p> + +<p>In 1852 he went with Koelliker to Messina<span class="pagenum"><a name="Page_98" id="Page_98">[Pg 98]</a></span> +to study the structure and development of the +marine fauna. Important papers on Siphonophora, +Echinoderms, Pteropoda, and, later, +Hydrozoa and Mollusca, were the result. +Soon after his return he was offered the +chair of Anatomy at Jena, and at this retired +spot he produced his most important works, +devoting himself more and more to the study +of the Vertebrata. Since 1875 he has held +the Chair of Anatomy at Heidelberg.</p> + +<p>In 1859 he published his 'Principles of +Comparative Anatomy'; but in 1870 he remodelled +it completely, the theory of descent +being the guiding principle. These 'Grundzüge' +were followed by a somewhat more +condensed 'Grundriss,' the second edition of +which was published in 1878, and has been +translated into French and English. In the +meantime he had broken new ground by +the development and treatment of certain +problems concerning the composition and +origin of the limbs, the shoulder-girdle and +the skull, researches which are embodied<span class="pagenum"><a name="Page_99" id="Page_99">[Pg 99]</a></span> +in his 'Untersuchungen zur vergleichenden +Anatomie der Wirbelthiere,' 1864-65-72.</p> + +<p>In 1883 he brought out a text-book on +human anatomy. This also marked a new +epoch, because for the first time, not only the +nomenclature, but also the general treatment +of human anatomy, was put upon a firm +comparative anatomical basis. The success +of this work is indicated by the fact that it +reached the sixth edition in 1897.</p> + +<p>Lastly, in 1898, appeared the first volume +of what may be called his crowning work, +'Vergleichende Anatomie der Wirbelthiere.'</p> + +<p>Gegenbaur is universally recognised, not +only as the greatest living comparative +anatomist, but also as the founder of the +modern side of this science, by having based +it on the theory of descent.</p> + +<p>In 1896 he received from the Royal Society +the Copley medal 'for his pre-eminence in +the science of comparative anatomy or animal +morphology.'</p> + +<p>His marvellously powerful influence as a<span class="pagenum"><a name="Page_100" id="Page_100">[Pg 100]</a></span> +teacher and investigator has made Heidelberg +a centre whence many pupils have +spread his teaching, and above all his method +of research.</p> + + +<p><span class="smcap">Ernst Heinrich Haeckel</span> was born on +February 16, 1834, at Potsdam. He carried +out his academical studies alternately at +Berlin and Würzburg, attracted by such +men as Johannes Mueller, Koelliker, and +Virchow. For years he was undecided what +his career should be, whether that of botanist, +collector, or geographical traveller. Certainly +that of medicine attracted him least, although +in deference to his father's wishes he qualified +and settled down for a year's practice in +Berlin. As he himself has told us, he might +perhaps have proved rather successful as a +physician, to judge from the fact that he did +not lose a single patient. But 'I had only +three patients all told, and the reason of this +is perhaps that I had given on my plate the +hours of consultation as from 5 to 6 <i>a.m.</i>'</p> + +<p><span class="pagenum"><a name="Page_101" id="Page_101">[Pg 101]</a></span></p> + +<p>During the year 1859 he travelled as +medical man and artist in Sicily. In 1861 +he was induced by Gegenbaur, whose acquaintance +he had made in Würzburg, to +establish himself as a <i>Privat-docent</i> for comparative +anatomy in Jena. And there he +has remained ever since, filling the Chair of +Zoology, and having declined several much +more tempting offers from the Universities of +Würzburg, Vienna, Strassburg, and Bonn.</p> + +<p>Within one year, 1865, he wrote the two +volumes of his 'Generelle Morphologie der +Organismen,' as he himself relates, in order +to master his sorrow over the loss of his first +wife. But he broke down, and went to the +Canaries to recruit health and strength. The +'Morphologie,' which has long been out of +print,<a name="FNanchor_26_26" id="FNanchor_26_26"></a><a href="#Footnote_26_26" class="fnanchor">[26]</a> made scarcely any impression. It<span class="pagenum"><a name="Page_102" id="Page_102">[Pg 102]</a></span> +was ignored, probably because he had placed +the old-fashioned study of zoology and morphology +upon a thoroughly Darwinistic basis.</p> + +<p>On the advice of his friend Gegenbaur, he +gave a more popularly written abstract of +his 'Generelle Morphologie'—in fact, the +substance of a series of his lectures—in +the shape of his 'Natürliche Schöpfungsgeschichte.' +This 'History of Natural +Creation,' which in 1898 has reached the +ninth edition (first edition translated into +English in 1873), had the desired effect. +So also had his '<a name="Footnote_42" id="Footnote_42"></a><a href="#FNanchor_42">Anthropogenie</a> oder +<a name="Footnote_47" id="Footnote_47"></a><a href="#FNanchor_47">Entwicklungsgeschichte</a> des <a name="Footnote_51" id="Footnote_51"></a><a href="#FNanchor_51">Menschen</a>,' the +fourth edition of which appeared in 1891.</p> + +<p>It was a lucky coincidence that Haeckel +had just finished his preliminary academical +studies, was entirely at leisure, and undetermined +to which branch of natural science +he should devote his genius, when Darwin's +great work was given to the world. Haeckel +embraced the new doctrine fervently, and, +as Huxley was doing in England, he spread<span class="pagenum"><a name="Page_103" id="Page_103">[Pg 103]</a></span> +it and fought for it with ever-increasing +vigour in Germany.</p> + +<p>With marvellous vigour and quickness of +perception he applied the principles of Evolution +or the theory of descent to the whole +organic world, and not only opened entirely +new vistas for the study of morphology, +but also worked them out and fixed them. +He was the first to draw up pedigrees of +the various larger groups of animals and +plants, filling the gaps by fossils or with +hypothetical forms (the necessary existence +of which he arrived at by logical deductions); +and thus he reconstructed the first universal +pedigree, a gigantic ancestral tree, from the +simple unicellular Amœba to Man. Of course +these pedigrees were entirely provisional, as +he himself has over and over again avowed; +but they are, nevertheless, the ideal which all +systematists and morphologists working upon +the basis of Evolution have since been seeking +to establish.</p> + +<p>Naturally he was vigorously attacked, not<span class="pagenum"><a name="Page_104" id="Page_104">[Pg 104]</a></span> +only by anti-Darwinians, or rather anti-Evolutionists, +but also by many of those +who, having accepted the principle of transformism, +ought to have known better. +Perhaps they thought they did know better. +Imperfections or mistakes in details of the +grand attempt,—and these, naturally, were +many,—were singled out as samples of the +whole, which was ridiculed as the romance +of a dreamer.</p> + +<p>In the end, however, this hostility, narrow-minded +and unfair in many respects, has done +good to the cause. There has arisen an +ever-increasing school of workers in favour +of the new doctrine. Owing to renewed +research, criticism, corrections in all directions, +we now know considerably more about +natural classification (and this is pedigree) +than when Haeckel first opened out the +whole problem.</p> + +<p>Owing to his fearless mode of exposition, +regardless of the indignant wrath which the +new doctrine aroused in certain ecclesiastical<span class="pagenum"><a name="Page_105" id="Page_105">[Pg 105]</a></span> +quarters, Haeckel bore the brunt of almost +endless attacks, and had to write polemical +essays. The result has been that friend and +foe alike are now working on the lines which +he has laid down; most of the ideas which +he was the first to conceive, and to formulate +by inventing a scientific terminology for +them, have become important branches, or +even disciplines, of the science.</p> + +<p>Most morphologists of the younger generations +now take these terms for granted, without +remembering the name of their founder. +It is, therefore, perhaps not quite superfluous +to mention some of them:</p> + +<p><i>Phylum</i>, or stem, the sum total of all those +organisms which have probably descended +from one common lower form. He distinguished +eight such phyla—Protozoa, +Cœlenterata, Helminthes or Vermes, Tunicata, +Mollusca, Articulata, and Vertebrata. +The phyla are more or less analogous to +'super-classes,' large branches or 'circles,' or +principal groups of other zoologists.</p> + +<p><span class="pagenum"><a name="Page_106" id="Page_106">[Pg 106]</a></span></p> + +<p><a name="Footnote_43" id="Footnote_43"></a><a href="#FNanchor_43"><i>Phylogeny</i></a>, +the history of the <a name="Footnote_48" id="Footnote_48"></a><a href="#FNanchor_48">development</a> of the various <a name="Footnote_52" id="Footnote_52"></a><a href="#FNanchor_52">phyla</a>, classes, orders, +families,and species.</p> + +<p><i>Ontogeny</i>, the history or study of the +development of the individual, generally +called embryology. In reality the scope of +embryology is the ontogenetic study of the +various species, and this branch of developmental +study alone can be checked by direct, +'exact' observation, for the simple reason +that the individuals alone are entities, while +the species, genera, families, etc., are abstract +ideas.</p> + +<p>The <i>ontogenesis of any given living organism +is a short, condensed recapitulation of its +ancestral history or of its phylogenesis</i>. This +is Haeckel's 'fundamental biogenetic law.'</p> + +<p>A complete proof of the phylogeny of any +creature would be given by the preservation +of an unbroken series of all its fossil ancestors. +Such a series will in most cases, for obvious +reasons, always remain a desideratum. In a +few cases, however, the desideratum is nearly<span class="pagenum"><a name="Page_107" id="Page_107">[Pg 107]</a></span> +met: for example, the ancestral line of the +one-toed digitigrade horse from a four-or +five-toed plantigrade and still very generalized +Ungulate is approaching completion.</p> + +<p>Phylogenetic study has to rely upon other +help. This is afforded by comparative +anatomy and by the study of ontogeny. +If the latter were a faithful, unbroken recapitulation +of all the stages through which +the ancestors have passed, the whole matter +would be very simple; but we know for +certain that in the individual development +many stages are left out (or, rather, are +hurried through, and are so condensed by +short-cuts being taken that we cannot +observe them), while other features which +have been introduced obscure, and occasionally +modify beyond recognition, the original +course.</p> + +<p>Again, the sequence of the appearance +of the various organs is frequently upset +(<i>heterochronism</i>). Some organs are accelerated +in their development, while others,<span class="pagenum"><a name="Page_108" id="Page_108">[Pg 108]</a></span> +which we know to be phylogenetically older, +are retarded in making their reappearance in +the embryo.</p> + +<p>These disturbing or distorting newly introduced +features or factors show themselves +chiefly in connection with the embryonic conditions +of growth—for example, yolk-sac, +placenta, amnion. They all come within the +category of <i>cænogenesis</i>: they are cænogenetic, +while the true, undisturbed recapitulation is +<i>palingenetic</i>.</p> + +<p>Lastly, some features, so-called rudimentary +or vestigial organs, instead of disappearing, +are most tenacious in their recurrence, while +others of originally fundamental importance +scarcely leave recognisable traces, and are, so +to speak, only hinted at during the embryonic +growth of the creature we happen to study. +Hence arises the philosophical study of +'Dysteleology.'</p> + +<p>Among other terms invented by Haeckel, +and now in general use, are <i>Metamere</i>, +<i>Metamerism</i>, <i>Cœlom</i>, <i>Gonochorism</i>, <i>Gastrula</i>,<span class="pagenum"><a name="Page_109" id="Page_109">[Pg 109]</a></span> +<i>Metazoa</i>, <i>Gnathostomata</i>, <i>Acrania</i>, <i>Craniota</i>, +and <i>Amniota</i>.</p> + +<p>Hitherto we have dealt with his general +work only, a résumé of which he gave for +many years in a course of thirty lectures +before an audience composed of 'all sorts +and conditions of men.' Students of biology +and of medicine side by side with theologians, +incipient and ordained, jurists, political economists, +and philosophers, crowded his lecture-room +during the 'seventies to hear the master +explaining the 'natural history of creation' or +the mysteries of anthropogenesis. Another +course of eighty lectures during the winter +semester was, and still is, devoted to a +systematic treatment of zoology, while practical +classes are reserved for the more select.</p> + +<p>His winning personality and fascinating +eloquence, combined with a clear and concise +delivery, have gained the enthusiastic admiration +of many a student who went to the quiet +University town in order to learn with his +own ears and eyes.</p> + +<p><span class="pagenum"><a name="Page_110" id="Page_110">[Pg 110]</a></span></p> + +<p><i>List of Separate Publications by Professor +Haeckel.</i></p> + +<p>'Biologische Studien. I.: Studien ueber +die Moneren und andere Protisten.' Leipzig, +1870 (out of print). He was the first to +make observations on the natural history of +the Monera, living bits of protoplasm, devoid +even of a nucleus—<i>e.g.</i>, <i>Protogenes primordialis</i>, +<i>Protomyxa aurantiaca</i>.</p> + +<p>'Monographie der Radiolarien.' Berlin, +1862-88. With 171 plates.</p> + +<p>'Entwicklungsgeschichte der Siphonophoren.' +Utrecht, 1869.</p> + +<p>'Plankton-Studien. Vergleichende Untersuchungen +ueber die Bedeutung und +Zusammensetzung der pelagischen Fauna +und Flora.' Jena, 1880.</p> + +<p>'Metagenesis und Hypogenesis von +Aurelia aurita.' Jena, 1881.</p> + +<p>'Monographie der Geryoniden oder +Ruesselquallen.' Leipzig, 1865.</p> + +<p>'Generelle Morphologie der Organismen.' +2 vols. Berlin, 1866.</p> + +<p><span class="pagenum"><a name="Page_111" id="Page_111">[Pg 111]</a></span></p> + +<p>'Anthropogenie oder Entwicklungsgeschichte +des Menschen,' 1874; 4th edition, +1891.</p> + +<p>'Natuerliche Schoepfungs-Geschichte.' 2 +vols. Berlin, 1st edition, 1868; 9th edition, +1898. This work has been translated into +most European languages (the first edition in +English, under the title 'Natural History of +Creation' in 1873; the eighth in 1892).</p> + +<p>'Monographie der Kalkschwaemme.' 3 +vols. Berlin, 1872 (out of print). With the +subtitle, 'An Attempt to solve analytically +the Problem of the Origin of Species.' In +this work, illustrated by sixty plates, he +showed that the Calcispongia are individually +so yielding, so adaptive to external influences, +that it is practically impossible to break up +the whole group into anything like satisfactory +species or genera. According to +predilection, we can distinguish either 1 genus +with only 3 species, or 3, 21, 43 genera, with +21, 111, 181, or 289 species respectively.</p> + +<p>In this work, in 1872, Haeckel established<span class="pagenum"><a name="Page_112" id="Page_112">[Pg 112]</a></span> +the homology of the two primary layers, ecto- +and endoderm, throughout the Metazoa. +The attempt to do the same for the four +secondary layers, as made in the second part +of his 'Gastræa-theory,' failed. It caused +an enormous amount of research, hitherto +without a satisfactory solution of the problem.</p> + +<p>'Studien zur Gastræa-Theorie.' Jena, +1874. The transformation of the single +primitive egg-cell by cleavage into a globular +mass of cells (Morula)—which latter, becoming +hollow (and then known as the Blastula), +turns ultimately by invagination or by delamination +into the Gastrula—is a series of +processes which applies to all Metazoa. The +Gastrula is, therefore, the ancestral form of +the Metazoa; and the Gastræa-theory, +founded by Haeckel, throws light, on the one +hand, upon the mystery of the phyletic connection +of the various animal groups, while, +on the other hand, it connects the Metazoa, +or multicellular organisms, with the lowest +Protozoa. We come to this conclusion because<span class="pagenum"><a name="Page_113" id="Page_113">[Pg 113]</a></span> +the Gastrula arises from and passes +through stages which exist as independent, +permanent organisms among the Protozoa.</p> + +<p>Needless to say this Gastræa-theory has +been violently attacked in detail, with the +result that various modifications of the Gastrula, +until then undreamed of, have become +known.</p> + +<p>'Monographie der Medusen.' Jena, 1879-81. +With 72 coloured plates.</p> + +<p>'Reports on the Scientific Results of the +Voyage of H.M.S. <i>Challenger</i>.' With 230 +plates:</p> + +<blockquote> +<p>1. Deep-sea Medusæ. 1881.<br /> +2. Radiolaria. 1887.<br /> +3. Siphonophoræ. 1888.<br /> +4. Deep-sea Keratosa. 1889.<br /> +</p></blockquote> + +<p>A short holiday spent on the coasts of the +Red Sea produced the volume 'Arabische +Korallen' (Berlin, 1876); and a longer trip +to Ceylon has been described in 'Indische +Reisebriefe,' of which the third edition<span class="pagenum"><a name="Page_114" id="Page_114">[Pg 114]</a></span> +appeared in 1893. The English translation +(1883) is entitled 'A Visit to Ceylon.'</p> + +<p>'Monism as connecting Religion and +Science: the Confession of Faith of a Man +of Science.' 1894.</p> + +<p>Haeckels latest work is the 'Systematische +Phylogenie' (Berlin, 1896), three volumes +dealing with Protistæ and Plants, Invertebrata +and Vertebrata. They contain the author's +views on the natural system of the organic +world, both living and extinct. Notable in +the work are the many reconstructions of +ancestral forms which, provided Evolution is +true, must have existed—hypothetical until +they, or something like them, are found in a +fossil state. Everybody who works systematically, +and upon the basis of Evolution, +does, sometimes unconsciously, reconstruct +such links, although he may perhaps not see +the necessity, or have the courage to fix +his vision, by assigning to it all those attributes +or characters which are indicated by +deductions from comparative anatomy, palæontology, +and embryology.</p> + +<p><span class="pagenum"><a name="Page_115" id="Page_115">[Pg 115]</a></span></p> + +<hr class="chap"/> +<div class="chapter-beginning"/> +<h2>THEORY OF CELLS.</h2> + + +<p>The vegetable cell was discovered by +<i>Schleiden</i>, Professor of Botany at Jena, in +1838. Next year <i>Schwann</i> found the animal +cell.</p> + +<p>In 1844 <i>Koelliker</i> discovered that the egg +cell, by division and multiplication, becomes +an aggregation—a heap of new cells.</p> + +<p>In 1849 <i>Huxley</i> found the two primary +layers (observed long before by <i>Pander</i> and +<i>Baer</i> in the chick) also in certain Invertebrata, +the Medusæ; and he called these layers +'ectoderm' and 'endoderm' respectively.</p> + +<p>In 1851 <i>Remak</i>, in his 'Untersuchungen +über die Entwicklung der Thiere,' showed +the egg to be a simple cell, and that from it, +by repeated division or multiplication, arise<span class="pagenum"><a name="Page_116" id="Page_116">[Pg 116]</a></span> +the germinal layers, and that by differentiation +of the cells of these layers are formed +all the tissues of the body.</p> + +<p><i>Kowalevsky</i>, of St. Petersburg, found the +two primary germinal layers also in Worms, +Echinoderms, Articulata, and other animals.</p> + +<p><i>Haeckel</i>, in 1872, found the same in the +Sponges. He stated that these two germinal +layers occur in all animals, except in the +Protozoa; and that they are homologous, +or equivalent, in all the groups of animals, +from the Sponges up to Man. In 1873, in +his 'Gastræa-theorie,' he explained the +phylogenetic significance, and tried to show +the homology, of the four secondary germinal +layers.</p> + +<p><span class="pagenum"><a name="Page_117" id="Page_117">[Pg 117]</a></span></p> + +<hr class="chap"/> +<div class="chapter-beginning"/> +<h2>FACTORS OF EVOLUTION.</h2> + + +<p>An organism, as living matter, does not +stand in opposition to, or outside of, the rest +of the world. It is part of the world. It +receives matter from its surroundings, and +gives some back; therefore it is influenced +by its surroundings. It is acted upon, and +it reacts upon the latter, and if these change +(and they are nowhere and never strictly the +same) the organism also <i>varies</i>. It <i>adapts</i> +itself, and if it does not, or, rather, cannot, +do so, it dies, because it is unfit to live in the +world, or, rather, in those particular surroundings +and conditions in which it happens to be. +That organism which yields most easily, accommodates +itself most quickly, has the best +chance of existence—<i>survival of the fittest</i>.<span class="pagenum"><a name="Page_118" id="Page_118">[Pg 118]</a></span> +'Fitness' in this case does not mean fitness +to live, but rather a particular condition which +happens to fit into the new circumstances.</p> + +<p>Adaptation and variation are simultaneous: +they are fundamentally the same. If there +were no adaptability and no variability, +those simplest of organisms which we suppose +to have sprung into existence in the +pre-Cambrian period would long ago have +ceased to exist.</p> + +<p>It is the physiological momentum which +models the organism, and, by causing its +adaptations, has produced its organs by +change of function. Gegenbaur illustrates +this most important fundamental truth by +an excellent example. Suppose that, in an +absolutely simple organism, all the parts of +its exterior are under the same functional +conditions, so that each part of the surface +can take in food, and that this is digested, +assimilated, in the interior. There is, in +this condition, not yet any definite organ. +If this organism sinks to the bottom and<span class="pagenum"><a name="Page_119" id="Page_119">[Pg 119]</a></span> +becomes sessile, this part is excluded from +taking in nourishing matter, while the +opposite surface alone remains, or becomes +more, fit for this function. Thus, a simple +variation and adaptation has been produced, +and if the same organism continues in this +position, its bottom cells will estrange themselves +from their original function, while +those on the top will convey the food into +the interior, where a cavity will be formed, +ultimately with a permanent opening, the +primitive gut and mouth, both very different +from the 'foot.'</p> + +<p>Thus, by adaptation and variation the +organism acquires new functions, organs, +features, and it gives up and eventually loses +others. Its offspring is like it. Like produces +like. This is the principle of <i>heredity</i>. +Adaptation, when going on generation after +generation on the same lines in the same +direction, becomes continuous, and has an +intensifying, <i>cumulative</i> effect. By always +weeding out from a flock of pigeons those birds<span class="pagenum"><a name="Page_120" id="Page_120">[Pg 120]</a></span> +which possess more dark feathers than the +rest, we ultimately produce an entirely white +race. We hurry on what Nature does slowly.</p> + +<p>The inheritance of acquired characters +becomes very obvious in the following +example: The Monera are the lowest living +organisms known; they consist of a mass of +protoplasm, and are still devoid of even a +nucleus. They multiply simply by division; +each half is like the other, and like the parent +(which by this process has ceased to exist), +except that each is smaller and has to grow. +A certain Moneron, <i>Protomyxa aurantiaca</i>, +is orange-coloured, and its offspring is from +the beginning of the same colour, and this +colour has been acquired by that kind of +Monera-like protoplasm which thereby has +become the species called Aurantiaca. We +have no reason for assuming that there +existed from the beginning of life not only +colourless, but also red, orange, and other +kinds of protoplasm. In these simplest of +organisms the whole process of heredity<span class="pagenum"><a name="Page_121" id="Page_121">[Pg 121]</a></span> +seems very obvious; but in the higher ones, +in those which propagate by eggs, the +problem is infinitely more complicated. It +is true that the egg is, strictly, nothing but a +small part of the parental organism, and we +know from everyday experience that this +single egg-cell has in it all the attributes and +characteristics of the parent; but these attributes +and characteristics make their appearance +successively, just as the egg cell of a +chick has neither wings nor feathers, not +even a backbone, but develops these organs +because its parents have them.</p> + +<p>The theory that acquired characters are +hereditary has often been vigorously attacked; +but the champions of the negative position +have not given us anything satisfactory +instead. They question, also, the principle +of adaptation as a factor in Evolution, and +substitute 'variation,' coupled with 'natural +selection.'</p> + +<p>They point to Darwin's argument: (1) It +is a fact that animals and plants produce a<span class="pagenum"><a name="Page_122" id="Page_122">[Pg 122]</a></span> +much greater number of young than in their +turn grow up to propagate the race; (2) no +two of the frequently many individuals of +the same breed are exactly alike, although +the differences may be hidden to our perception +(this is quite true, because no two +entities can live in absolutely the same place +and conditions); (3) through heredity the +offspring takes over the faculties and features +of the parents; (4) what decides which of +the many individuals (each one possessing +some aberration or variation) are to live and +to propagate the race?—obviously those +individual variations which happen to make +the lucky possessors most fit for the struggle +for life.</p> + +<p>So far, well; but the 'Neo-Darwinians' +imagine that 'adaptation' is not the cause, but +the result, the effect, of the formation of +species. According to them, the species are +neither adapted by, nor do they adapt themselves +to, their surroundings. Adaptation is to +them an accomplished fact, a condition which a<span class="pagenum"><a name="Page_123" id="Page_123">[Pg 123]</a></span> +species happens to be in because its particular +variation is the one which, to the exclusion +of others, suits or fits into its surroundings. +Such a view simply takes variation for +granted, and stipulates it as a something +<i>a priori</i>, without raising the further necessary +question, why there should be any +variations at all. Why, indeed, unless they +are caused by external influences? Haeckel +elucidated this by the conception of adaptation +as explained in the foregoing pages.</p> + +<p>These and kindred speculations have produced +some rather curious discussions, which +not infrequently end in conundrums. If we +speak of a case of adaptation as a condition, a +fact, we easily run the risk of getting into confusion +about cause and effect. For example: Is +the stag swift because he has long and slender +legs, or are his legs long because he is swift? +In reality, swiftness and length of legs are +cause and effect in one. His legs have been +so modified as to make him swift, because he +has put them continuously to whatever was<span class="pagenum"><a name="Page_124" id="Page_124">[Pg 124]</a></span> +his full speed, which in his thick-footed +ancestors was probably a very slow one. +The above question reads, therefore, more +sensibly as follows: Has the stag become +swift because his legs have become long and +slender, or have his legs become long and +slender because he has attained swiftness? +Now, we see that both halves of the double +question are practically the same and instantly +suggest the answer.</p> + +<p>A fundamental difference between artificial +machines and living organisms is that the +former are worn out by use, while the latter +not only repair the loss caused by use, but are +also stimulated to further increase. On the +other hand, organs which are not put into +function, or are not used, <i>degenerate</i>. The +various cells of the organ react upon external +stimuli by increased activity. Why this should +be so is another question—perhaps because +those which do not would soon be not fit to +survive. Each cell has a function; the more +specialized the more intense it is. Every<span class="pagenum"><a name="Page_125" id="Page_125">[Pg 125]</a></span> +external stimulus, every contact with the +outer surroundings, is an insult, necessarily +of detrimental effect, as it disturbs the equilibrium +of the cell body. It must, therefore, +be of advantage to the cells' well-being to +return as soon as possible to the <i>status quo +ante</i>, and this can only be done by increased +activity.</p> + +<p>In the present state of our knowledge, +we can approach only the simplest cases of +acquisition of characteristics. Mostly they +are so complicated, subject to so many unthought-of +conditions, that we do not know +from which end to approach the problem. +Frequently the supposed use of certain +obvious features is the merest guesswork. +This applies especially to features to which +we are not accustomed (although wrongly +so) to assign a function—for example, coloration. +A green tree-frog will with predilection +rest on green leaves. The advantages +of concealment are obvious, and in this case +he 'adapts himself' to the surroundings by<span class="pagenum"><a name="Page_126" id="Page_126">[Pg 126]</a></span> +making for green localities: if he did not +he would be eaten up sooner than his more +circumspect comrades. But this making for, +and sitting in, the green has not <i>necessarily</i> +made him of that colour. Extreme advocates +of one view would argue as follows: +Once upon a time there were among the +offspring of ancestral tree-frogs some which, +among other colours, exhibited green, not +much, perhaps not even perceptible to our +eyes. The occurrence of this colour, according +to them, was spontaneous, a freak—as if +in reality there were anything spontaneous +in the sense of being causeless. The +descendants of these more greenish creatures, +provided they did not pair with frogs of the +ordinary set, became still greener (by accumulative +inheritance), and so on, until the green +was pronounced sufficient to be of advantage +when competition could set in.</p> + +<p>With this view there is always the difficulty +of understanding how the initial very +small changes can be useful, unless we have<span class="pagenum"><a name="Page_127" id="Page_127">[Pg 127]</a></span> +to deal with extremely simple organisms. Is +it likely in the case of our frogs that an +almost imperceptible variation in colour makes +them more fit to live? We have to assume +that 'luck' or chance kept them for generations +out of harm's reach, until the accumulation +of green, hitherto quite ineffective, +neither harmful nor useful, became strong +enough to be effective. Such cases undoubtedly +happen.</p> + +<p>But we can also argue out this problem +in a somewhat different way, which goes +nearer to the root of the whole process. The +original slight, imperceptible change in pigmentation +is not a spontaneous freak; it was +caused by the direct influence of the surroundings +in which the particular frogs +happened to live, be this factor light or +temperature or food. Thus it stands to +reason that the offspring, living under similar +conditions, will be acted upon in the same +way. That factor which has added green to +the parents will add green to the children,<span class="pagenum"><a name="Page_128" id="Page_128">[Pg 128]</a></span> +until by accumulative inheritance a more +decidedly green race is produced.</p> + +<p>The offspring of green plants do not +become green when grown in the dark; the +young plants inherit not the green, but the +capacity of becoming green when acted upon +by sunlight. This as an instance of direct +influence of the surroundings on a substance +(chlorophyll), which has not yet performed a +function. But the kittens of a pair of black +cats produce black hair before they are born, +and we have no reason to doubt that the +black pigment in their tegumentary structures +is ultimately referable to the action of the +sunlight. In many instances creatures living +for generations in darkness become white, +pigmentless, and they regain it when exposed +to light. For example, the white, colourless +Proteus from the caves of Adelsberg becomes +clouded grey, and ultimately jet black, when +kept in a tank whence light is not strictly +excluded.</p> + +<p>Blindness is a very general characteristic<span class="pagenum"><a name="Page_129" id="Page_129">[Pg 129]</a></span> +of creatures which dwell in darkness. There +are all stages between total blindness and +weak eyes. Now, do these blind creatures +live in darkness because they are blind, or +have they become first weak-eyed and then +blind because of the continuous disuse of +their eyes? The former explanation has +actually been suggested! Individuals not +smitten, but spontaneously, as a freak, born +with sore eyes, have crept into the darkness +for relief and have produced a blind race! +To carry such a notion to the bitter end leads +to absurdities. Anyhow, it is not understandable +where the benefit of losing the +eyesight arises. It can be explained only +by continued disuse: witness <i>Spalax typhlus</i>, +the blind mole, and, above all, the Endoparasites.</p> + +<p>Let us now take an example to explain the +influence of a tangible external stimulus. +Repeated pressure produces callosities. +Although they are not exactly beneficial +in the shape of corns on our toes, they are<span class="pagenum"><a name="Page_130" id="Page_130">[Pg 130]</a></span> +so on our hands. At any rate, the morphologist +can trace the development of the +footpads, nails, hoofs, and horns, step by +step from small beginnings. The cells of +the Malpighian stratum, of the inner, active +portion of our epidermis, are excited to extra +activity, and by continually producing more +horn cells than peel off the surface of the +skin in the normal process of wear and tear +cause the formation of the pad. It need +scarcely be mentioned that hypertrophic +growths are not necessarily useful; they are +often harmful, and in that case pathological.</p> + +<p>Lastly, a few words about the very difficult +question of <i>teleology</i>. In trying to explain +Evolution in a mechanical—sometimes called +monistic, but in reality natural—way, we +exclude anything like a set purpose, a goal, +or ideal, a final condition which the organism +strives to attain. Unknown, however, to +many morphologists, especially embryologists, +their writings are full of this teleological +notion. Indeed, there are many cases<span class="pagenum"><a name="Page_131" id="Page_131">[Pg 131]</a></span> +in which an organism becomes changed, and +quickly, too, in a way which cannot but be +called reasonable. It starts modifications, be +they outgrowths, alterations in shape or colour, +or the making good of injuries received, +which by 'short-cuts' produce the only +advantageous result that can reasonably +satisfy the new requirement or altered circumstances.</p> + +<p>Trees growing in precarious positions, +after part of the supporting rock has slipped +away, throw out new roots, and rearrange some +of the old ones in the only way which could +save the tree. In animals which have lost part +of a limb the wound closes up, and what is left +is turned into a serviceable stump—for +example, in water-tortoises (creatures in which +reproduction of lost limbs does not happen). +In frogs and newts the lost part is reproduced, +not correctly, but in a good semblance. +Tortoises which have had their shell smashed +can throw off an astonishingly large portion +and renew the bone as well as the over<span class="pagenum"><a name="Page_132" id="Page_132">[Pg 132]</a></span>lapping +scutes; but this mending is not neatly +done. It serves the requirement, but it is +patchwork; the new shell is such as no +tortoise ever possessed before.</p> + +<p>Mammals transported into colder countries, +or subjected to continued exposure, grow a +thicker coat; and the same kind of tree +which in a sheltered valley is tall, large-leaved, +and soft-wooded, assumes a very +different aspect, although perhaps growing +into a healthy specimen, when planted on a +wind-exposed hill.</p> + +<p>There is no room, or, rather, no time, to +apply to these cases the principle of many +variations or the long-continued accumulation +of infinitely small changes. The thing is to +be done quickly, or not at all. Nor can we +explain the mending of a wound, which +implies an activity of countless cells, simply +as a case of, or similar to, the reproduction +of a lost part; against such an +explanation militates the almost absolute +unlikelihood of that precise injury having<span class="pagenum"><a name="Page_133" id="Page_133">[Pg 133]</a></span> +happened before to any of the creature's +ancestors.</p> + +<p>Still, I think we are brought near the solution +of the mystery by such considerations. +We see no difficulty in the regeneration of a +few cells, or in the making good of the disturbance +suffered by one of the most simple +organisms; but we become suspicious when +we see that countless cells, not of one kind, +but of the most varied tissues and parts of +the body, make common cause in remedying +a defect in a serviceable way.</p> + +<p>We must assume that since the beginning +of life organisms have been subjected to +countless insults. We can scarcely speak of +a wound in an Amæba; but these insults +have always been made good, and whenever +this was not the case, that particular organism +came to an end. As these organisms developed +into more complicated ones, the +possible insults became more serious, more +complicated; and the organisms took adaptive +measures so as to be superior to them. This<span class="pagenum"><a name="Page_134" id="Page_134">[Pg 134]</a></span> +action, I have no hesitation in declaring, +became by heredity a habit. The whole +creature became so thoroughly 'imbued' (for +want of a better word) with the finding of +ways and means for meeting sudden, serious +conditions, that it now acts directly, and +produces by a short-cut, with the least amount +of time and with the smallest possible waste +of material, that which meets the occasion, +thereby saving the life of the individual and +that of the race. This we cannot but call +reasonable and to the purpose, although it is +all carried out by <i>causæ efficientes</i> without +there being any <i>causæ finales</i>.</p> + +<p><span class="pagenum"><a name="Page_135" id="Page_135">[Pg 135]</a></span></p> + +<hr class="chap"/> +<div class="chapter-beginning"/> +<h2>GEOLOGICAL TIME AND EVOLUTION.</h2> + + +<p>One million years is a stretch of time beyond +our conception. We can arrive at a more or +less adequate understanding of what a million +individuals or concrete things means. Several +Continental nations can put more than a +million men into the field. We can gaze at +a building which contains as many bricks; +and we know that our own body is composed +of millions of millions of cells. No +such help applies to time, because that itself +is an entirely relative, abstract conception. +We can imagine what one hundred years are +like—a span of time seemingly short to the +hale and hearty octogenarian, enormous to +the child, totally inapplicable to certain<span class="pagenum"><a name="Page_136" id="Page_136">[Pg 136]</a></span> +animals whose whole life is crowded into one +single day.</p> + +<p>Astronomers have long ceased to reckon +distances by miles or any other understandable +unit. They express the distances +between us and the stars and nebulæ by +'years of light.' Try to imagine a unit of +length equal to that which is passed through +by light (186,000 miles per second) in one +year. Not so very long ago the enormous +distances resulting from astronomical calculations +were looked upon as the most serious +objection to the correctness of the astronomers' +views as to the distances which separate our +globe from the nearest fixed stars. We have +not yet accustomed ourselves to reckoning +time by some similar broadly-conceived +standard—say æons of so many thousand +years each.</p> + +<p>Unfortunately, we possess no data whatever +for calculating the age of the successive +geological strata. Thanks to Lyell, the +theory of violent universal cataclysms has<span class="pagenum"><a name="Page_137" id="Page_137">[Pg 137]</a></span> +been done away with. It is more probable +that the same agencies have acted which are +now changing the aspect of the globe; and +these changes are slow, as far as we know +them—at least, as far as the formation of +sedimentary strata is concerned, and these +alone we have to deal with. Various calculations +have been made, based upon the +denudation of the mountains, the filling up of +the valleys by the débris, the formation of +deltas, etc. The results give enormous +stretches of time, but all of them unsatisfactory, +because the methods are so very local in +their application.</p> + +<p>The least objectionable attempt is that +which, based upon astronomical calculations, +tried to fix the height of the last Glacial +epoch<a name="FNanchor_27_27" id="FNanchor_27_27"></a><a href="#Footnote_27_27" class="fnanchor">[27]</a> at about 200,000 years ago, and +asserted that since its beginning in the +Pliocene epoch as many as 270,000 years +have elapsed. The duration of the whole<span class="pagenum"><a name="Page_138" id="Page_138">[Pg 138]</a></span> +Tertiary period has by the same authorities +been fixed approximately at 3,000,000 to +4,000,000 years. Beyond this we cannot venture +without the wildest speculation; but we +know to a certain extent the thickness of the +various sedimentary strata, which amount in +all to from 100,000 to 175,000 feet—on the +average perhaps 130,000 feet, or about twenty +miles.</p> + +<p>Unless we prefer giving up all attempt +at calculation as absolutely hopeless, and +thus resign the whole problem, we must at +least try to arrive at some results, and then +see if these cannot reasonably be made use of.</p> + +<p>Neither geologist nor physicist, and no +zoologist, would accept the suggestion that +these 130,000 feet of stratified rocks have +been deposited within only as many years, +although the average rate of deposit would +in that case be not more than 1 foot per +year. On the other hand, an indignant protest +is raised against the assumption of +1,000,000,000 years.</p> + +<p><span class="pagenum"><a name="Page_139" id="Page_139">[Pg 139]</a></span></p> + +<p>Lord Kelvin<a name="FNanchor_28_28" id="FNanchor_28_28"></a><a href="#Footnote_28_28" class="fnanchor">[28]</a> has come to the conclusion +(from data which various other authorities +regard as very unsatisfactory) that not +much more than 100,000,000 years can have +elapsed since the molten globe acquired a +consolidated crust. Further time must have +passed before the surface had become stable +and cool enough to allow the temperature of +the collecting oceans to fall below boiling-point, +and it is obvious that life cannot +possibly have begun until after this had +happened.</p> + +<p>Wallace, in his 'Island Life,' by making +use of Professor A. Geikie's results as to the +rate of denudation of matter by rivers from +the area of their basins, and estimating the +average rate of deposition, concludes that +'the time required to produce this thickness +of rock [Professor Haughton's maximum of +177,000 feet] at the present rate of denudation +and deposition is only 28,000,000 years.'<span class="pagenum"><a name="Page_140" id="Page_140">[Pg 140]</a></span> +Our lower assumption of 130,000 feet thickness +would give only 20,000,000 years—a +rate of 1 foot in 154 years.</p> + +<p>Again, if we prefer round numbers to start +with, we have only to assume that the age of +the whole Tertiary period, with its 3,000 feet +thickness, is 3,000,000 years (<i>i.e.</i>, 1,000 feet +in 1,000,000 years, or 1 foot in 1,000 years, +surely an excessively slow rate); then +130,000,000 years would bring us to the +bottom of the Laurentian or pre-Cambrian +deposits. Of course, it is a pure assumption +that the same rate of destruction and sedimentation +applies to the whole of the strata; +but we know nothing to the contrary, especially +if we consider the average periods, the +quick periods of extra activity, taken with the +slow periods or those of standstill.</p> + +<p>Dana estimated the length of the whole +Tertiary period at one-fifteenth of the Mesozoic +and Palæozoic combined. If we take +the duration of the Tertiary period, as before, +as 3,000,000 to 4,000,000 years, the total<span class="pagenum"><a name="Page_141" id="Page_141">[Pg 141]</a></span> +will amount to from 45,000,000 to 60,000,000 +years.</p> + +<p>Lastly, Walcott<a name="FNanchor_29_29" id="FNanchor_29_29"></a><a href="#Footnote_29_29" class="fnanchor">[29]</a> has estimated the duration +of the Palæozoic, Mesozoic, and Cænozoic +or Tertiary epochs at about 17,000,000, +7,000,000 and 3,000,000 years respectively, +giving 27,700,000 years from the beginning +of the Cambrian; and Williams<a name="FNanchor_30_30" id="FNanchor_30_30"></a><a href="#Footnote_30_30" class="fnanchor">[30]</a> has calculated +the relative duration of the smaller +epochs. See the table on p. 149.</p> + +<p>The results of all these calculations fall +surprisingly well within the limits of Lord +Kelvin's allowance. Of course they are +based upon assumptions, but none of them +is inherently unreasonable; and it was my +purpose to draw attention to the surprising +coincidence in the closeness of these results, +perhaps too good to be true. Such calculations +are considered close enough if they +range within a few multiples of each other.</p> + +<p><span class="pagenum"><a name="Page_142" id="Page_142">[Pg 142]</a></span></p> +<p>Zoologists have fallen into the habit of +requiring enormous lengths of time for the +evolution of the animal kingdom. We know +that Evolution is at best a slow process, and +the conception of the changes necessary to +evolve man from monkey-like creatures, these +from the lowest imaginary mammals, these +from some reptilian stock, thence descending +to Dipnoan fish-like creatures, and so on +back into Invertebrata, down to the simple +Monera—this conception is indeed gigantic. +Innumerable, almost endless, slow changes +require seemingly unlimited time, and as time +is endless, why not draw upon it <i>ad libitum</i>?</p> + +<p>Huxley pointed out that it took nearly the +whole of the Tertiary epoch to produce the +horse out of the four-toed Eohippos, and +that, if we apply this rate to the rest of +its pedigree, enormous times would be required. +This is, however, a very misleading +statement, which necessitates considerable +reduction, in conformity with our increased +palæontological knowledge. Animals of the<span class="pagenum"><a name="Page_143" id="Page_143">[Pg 143]</a></span> +genus Equus—namely, Ungulata, with one +toe, and with a certain tooth pattern—from +the Upper Miocene of India are now known. +Moreover, it is not simply a question of the +gradual loss of the side-toes. The change +from the fox-sized little Eohippos and Hyracotherium, +so far as skull, teeth, vertebral +column, and limbs are concerned (about the +soft parts we know next to nothing), is a +very great one indeed.</p> + +<p>Elephants and mammoths seem to have +developed very rapidly. None are known +from Eocene strata; but towards the end +of the Miocene they had spread over Asia, +Europe, and North America, and that in +great numbers. The Eocene Amblypoda +are still so different that we hesitate to connect +them ancestrally with the elephants.</p> + +<p>The Pinnipedia (seals and walruses) are +strongly modified fissiped Carnivora, and have +existed since at least the Upper Miocene; +the transformation must have been accomplished +within the Miocene period.</p> + +<p><span class="pagenum"><a name="Page_144" id="Page_144">[Pg 144]</a></span></p> + +<p>We cannot shut our eyes to the fact that +various groups have from the time of their +first appearance burst out into an exuberant +growth of modifications in form, size, and +numbers, into all possible—and one might +almost say impossible—shapes; and they +have done this within comparatively short +periods, after which they have died out not +less rapidly. It seems almost as if these go-ahead +creatures had, by accepting every +possible modification and carrying the same +to the extreme, too quickly exhausted their +plasticity—which, after all, must have limits—thereby +becoming unable to meet successfully +the requirements of further changes in their +surroundings. The slowly developing groups, +keeping within main lines of Evolution, and +not being tempted into aberrant side-issues, +had, after all, a much better chance of onward +evolution.</p> + +<p>A good example of the former are the +Dinosaurs. We do not know their ancestors; +but we have here to deal only with their<span class="pagenum"><a name="Page_145" id="Page_145">[Pg 145]</a></span> +range of transformation. The oldest known +forms occur in the Upper Trias; they attain +their most stupendous development in the +Upper Jurassic and in the Wealden; and +they have died out with the Cretaceous epoch. +But already some of their earliest forms had +assumed bipedal gait, and the Oolitic Compsognathus +had developed almost bird-like hind-limbs.</p> + +<p>On the other hand, there are many +instances of extremely slow development—facts +which raise the difficult question of +'persistent types.' Are these due to a state of +perfection which cannot be improved upon? +Or are they due to a kind of morphological +consolidation (not necessarily specialization) +which can no longer yield easily, so that therefore +through changes in their surroundings +they may come to an end sooner than more +plastic groups?</p> + +<p>Struthio, the ostrich; Orycteropus, the +Cape ant-eater; Tapirus, and many others, +existed in the Miocene age practically as<span class="pagenum"><a name="Page_146" id="Page_146">[Pg 146]</a></span> +they are now; but pre-Pliocene dolphins, +cats, monkeys, stags, all belong to closely-allied +and well-defined 'genera,' but different +from the living forms.</p> + +<p>Alligators and crocodiles are known from +the Upper Chalk; Tomistoma since the +Miocene; Gavialis since the Pliocene.</p> + +<p>The oldest surviving reptile is Sphenodon, +the Hatteria of New Zealand, a fair representative +of what generalized reptiles of the +later Triassic period seem to have been like; +and to the same period belongs Ceratodus, +the Australian mud-fish, hitherto the oldest +known surviving genus of a very ancient and +low type so far as Vertebrata are concerned.</p> + +<p>Now let us see if the above estimates of +geological time are so utterly inapplicable to +animal evolution. On purpose we take one +of the lowest estimates, about 28,000,000 +years, and apportion them equally to the +various strata or epochs.</p> + +<p>The original owner of the famous Trinil +skull, a <i>Pithecanthropus erectus</i>, lived,<span class="pagenum"><a name="Page_147" id="Page_147">[Pg 147]</a></span> +according to some, in the Late Pliocene, +according to others in the Early Plistocene, +period—that is to say, somewhere about +the beginning of our last Glacial epoch, +some 270,000 years ago. Assuming that +he and his like reached puberty at sixteen +to twenty years of age, about 17,000 generations +would lie between him and ourselves, +or, to put it more forcibly, between +him and the lowest living human races—say +the Ceylonese Veddahs. Only 250 generations, +at twenty years, carry us back to +3000 <span class="smcap">B.C.</span> (<i>i.e.</i>, beyond the ken of history); and +if it be objected that the differences between +the oldest inhabitants of Egypt, the Naquada, +and the present Fellahin are very slight, +we are welcome to multiply these differences +sixty or seventy fold, in order to arrive at the +Pithecanthropus level. But these Naquada +had no metal implements, and there cannot be +the slightest doubt that the development of +the human race went on by leaps and bounds +after certain discoveries had been made—to<span class="pagenum"><a name="Page_148" id="Page_148">[Pg 148]</a></span> +wit, the use of implements and that of fire. +That creature which first took up a stone or +a branch and wielded it thereby got such an +enormous advantage over his fellow-creatures +that his mental and bodily development went +on apace. The same applies to the improvement +of speech. We assume the single, +monophyletic origin of mankind at one place, +in one district; and the differences between +some of the races of man are great enough +to constitute what we might call species. +Compare the Venus of Milo, that noble expression +of the ancient Greeks' notion of +female beauty, with the 'products of art' of +the Veddahs or the dwarfs of Central Africa, +or think of the beau-idéal which a Michael +Angelo could possibly have evolved if he had +never seen any but such people.</p> + +<p><span class="pagenum"><a name="Page_149" id="Page_149">[Pg 149]</a></span></p> + +<div style="line-height:90%"> +<table id="tae" summary="time" cellpadding="1" cellspacing="0" rules="cols" frame="box"> +<tr style="border:1px solid black;"> + <td class="tdc">I.</td> + <td class="tdc">II.</td> + <td class="tdc" >III.</td> + <td class="tdc" >IV.</td> + <td class="tdc" >V.</td> + <td class="tdc" >VII.</td> + <td class="tdc">VII.</td> +</tr> +<tr> + <td class="tdl">Recent</td> + <td class="tdl">}</td> + <td class="tdl" ></td> + <td class="tdl" ></td> + <td class="tdl" >Adam and Eve</td> + <td class="tdr" ></td> + <td class="tdr">250</td> +</tr> +<tr> + <td class="tdl"> Plistocene</td> + <td class="tdl">} 5</td> + <td class="tdl" >}</td> + <td class="tdl" >}</td> + <td class="tdl" >Man, contemp-</td> + <td class="tdr" ></td> + <td class="tdr">3,500</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" >} 270,000</td> + <td class="tdl" > orary with Reindeer</td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl"></td> + <td class="tdl" >}</td> + <td class="tdl" >}</td> + <td class="tdl" > in France</td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Pliocene -</td> + <td class="tdl">}</td> + <td class="tdl" >} 3,000,000</td> + <td class="tdl" ></td> + <td class="tdl" >Pithecanthropus</td> + <td class="tdr" >16</td> + <td class="tdr">17.000</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" >} 600,000</td> + <td class="tdl" > erectus</td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Miocene -</td> + <td class="tdl">}10</td> + <td class="tdl" >}</td> + <td class="tdl" ></td> + <td class="tdl" >Anthropoid</td> + <td class="tdr" >10</td> + <td class="tdr">60,000</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">}</td> + <td class="tdl">}</td> + <td class="tdl" >} 2,100,000</td> + <td class="tdl" > Apes</td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Eocene -</td> + <td class="tdl">}</td> + <td class="tdl" ></td> + <td class="tdl" >}</td> + <td class="tdl" >Lemurs</td> + <td class="tdr" >5</td> + <td class="tdr">420,000</td> +</tr> +<tr> + <td class="tdl">Cretaceous -</td> + <td class="tdl"> 10</td> + <td class="tdl" >}</td> + <td class="tdl" > 3,600,000</td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Jurassic -</td> + <td class="tdl"> 5</td> + <td class="tdl" >}</td> + <td class="tdl" > 1,800,000</td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Rhætic -</td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" >}</td> + <td class="tdl" >Prototheria, or</td> + <td class="tdr" >3</td> + <td class="tdr"> 1,800,000</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" >}</td> + <td class="tdl" > first Mammalia</td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">}</td> + <td class="tdl" >} 7,200,000</td> + <td class="tdl" >}</td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Keuper -</td> + <td class="tdl">} 5</td> + <td class="tdl" >}</td> + <td class="tdl" >}1,800,000</td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Muschelkalk -</td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" >}</td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">New Red</td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" >}</td> + <td class="tdl" >Theomorpha</td> + <td class="tdr" >4</td> + <td class="tdr">425,000</td> +</tr> +<tr> + <td class="tdl"> Sandstone </td> + <td class="tdl"></td> + <td class="tdl" ></td> + <td class="tdl" ></td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Magnesian</td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" >}</td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl"> Limestone</td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" >}</td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Lower Red</td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" >}</td> + <td class="tdl" >Proreptilia</td> + <td class="tdr" >4</td> + <td class="tdr">250,000</td> +</tr> +<tr> + <td class="tdl"> Sandstone</td> + <td class="tdl">}15</td> + <td class="tdl" >}</td> + <td class="tdl" >}4,000,000</td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Coal-measures</td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" >}</td> + <td class="tdl" >Eotetrapoda</td> + <td class="tdr" >4</td> + <td class="tdr">500,000</td> +</tr> +<tr> + <td class="tdl">Mountain</td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" >}</td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl"> Limestone</td> + <td class="tdl">}</td> + <td class="tdl" >}17,500,000</td> + <td class="tdl" >}</td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> + +<tr> + <td class="tdl">Devonian -</td> + <td class="tdl"> 15</td> + <td class="tdl" >}</td> + <td class="tdl" >4,000,000</td> + <td class="tdl" >Dipnoi and</td> + <td class="tdr" >5</td> + <td class="tdr">1,000,000</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl"></td> + <td class="tdl" >}</td> + <td class="tdl" ></td> + <td class="tdl" > Crossopterygii</td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Silurian -</td> + <td class="tdl"> 10</td> + <td class="tdl" >}</td> + <td class="tdl" >2,700,000</td> + <td class="tdl" >First fishlike</td> + <td class="tdr" >3</td> + <td class="tdr">900,000</td> +</tr> +<tr> + <td class="tdl"></td> + <td class="tdl">}</td> + <td class="tdl" >}</td> + <td class="tdl" ></td> + <td class="tdl" > creatures</td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Ordovician -</td> + <td class="tdl"> 10</td> + <td class="tdl" >}</td> + <td class="tdl" >2,700,000</td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Cambrian -</td> + <td class="tdl"> 15</td> + <td class="tdl" >}</td> + <td class="tdl" > 4,000,000</td> + <td class="tdl" >Sum total of</td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +<tr> + <td class="tdl">Laurentian -</td> + <td class="tdl"></td> + <td class="tdl" ></td> + <td class="tdl" ></td> + <td class="tdl" > generations</td> + <td class="tdr" ></td> + <td class="tdr">————</td> +</tr> +<tr> + <td class="tdl">Archean or</td> + <td class="tdl"></td> + <td class="tdl" ></td> + <td class="tdl" ></td> + <td class="tdl" > (about)</td> + <td class="tdr" ></td> + <td class="tdr">5,375,000</td> +</tr> +<tr> + <td class="tdl"> Metamorphic</td> + <td class="tdl"></td> + <td class="tdl" ></td> + <td class="tdl" ></td> + <td class="tdl" ></td> + <td class="tdr" ></td> + <td class="tdr"></td> +</tr> +</table> +</div> +<p><span class="pagenum"><a name="Page_150" id="Page_150">[Pg 150]</a></span></p> + +<p><span class="smcap">Explanation of the Table on p. 149.</span></p> + +<blockquote> + +<p>Column I. contains the names of the successive sedimentary +strata.</p> + +<p> " II. contains the percentage of the duration of the +various epochs, according to <i>Williams</i>, the +time from the Cambrian until recent times +being taken as 100.</p> + +<p> " III. gives the estimated duration in years of the +Palæozoic, Mesozoic, and Cænozoic periods, +according to <i>Walcott</i>.</p> + +<p> " IV. gives in years the duration of the various +smaller epochs, as computed from Walcott and +Williams' statements.</p> + +<p> " V. Representatives of stages of the ancestral line of +man. The names stand in the level of the +stratum in which they have made their first +appearance.</p> + +<p> " VI. contains the number of years which, in the present +calculation, have been assumed necessary for +the animal to reach puberty.</p> + +<p> " VII. contains the number of generations which can +have elapsed from stage to stage. For example, +60,000 generations separate the earliest known +anthropoid apes from Pithecanthropus.</p> +</blockquote> + +<p>Let us follow the descent of man further +back. The next stage, reckoning backwards, +is that from Pithecanthropus to <i>bonâ-fide</i> +anthropoid apes. They are represented in +the Miocene by various genera—<i>e.g.</i>, Pliopithecus +and Dryopithecus. According to +Croll and Wallace, 850,000 years ago carry us<span class="pagenum"><a name="Page_151" id="Page_151">[Pg 151]</a></span> +into the Miocene epoch. Assuming that +these apes lived about 600,000 years before +Pithecanthropus, namely, in the later half of +the Miocene, and taking puberty at ten years +of age, a high estimate, we get not less than +60,000 generations.</p> + +<p>2. From Apes back to lowest Lemurs in +the lowest Eocene. The date of Eocene +being fixed at 3,000,000, we have about +2,100,000 years for this stage; assuming as +much as five years for puberty, this results in +420,000 generations.</p> + +<p>3. From Lemures to Prototheria. The +earliest known mammalian remains come +from the Rhætic, or top formation of the +Triassic epoch; allowing for the Rhætic +only 100,000 years, we have to add the +whole of the Jurassic and Cretaceous, in all +about 5,500,000 years. Assuming three +years for a generation, we get 1,800,000 +generations.</p> + +<p>4. From Prototheria to something like the +Theromorpha at the bottom of the Triassic<span class="pagenum"><a name="Page_152" id="Page_152">[Pg 152]</a></span> +strata. A duration of 1,700,000 years divided +by four gives 425,000 generations.</p> + +<p>5. From Theromorpha to Proreptilia, +represented by Eryops and Cricotus from +the Lower Permian of Texas. Allowing +1,000,000 years, each generation at four +years, we obtain 250,000 generations.</p> + +<p>6. From Proreptilia to Eotetrapoda, the +first terrestrial Vertebrata, represented by +something like the Stegocephali, the earliest +of which are known from the Coal-measures. +Assuming them to have come into existence +at the bottom of the Coal-measures, for the +duration of which we may guess 2,000,000 +years, we get, with four years' allowance for +puberty, 500,000 generations.</p> + +<p>7. From Eotetrapoda to a not yet separated +or differentiated group of Crossopterygian +and Dipnoan fishes, both of which +are known from Devonian strata. The +duration of the latter has been computed at +4,000,000 years, which, with 1,000,000 for +the Mountain Limestone formation, gives us<span class="pagenum"><a name="Page_153" id="Page_153">[Pg 153]</a></span> +5,000,000 for this stage. Assuming, for the +sake of round numbers, as much as five +years for a generation, we get 1,000,000 +generations.</p> + +<p>8. Earliest stage, down to the first fish-like +creatures. Teeth and spines indicating the +existence of fishes are known from the Upper +Silurian. By carrying the earliest fishes down +to the bottom of the Silurian, with 2,700,000 +years' duration, and allowing three years for +attaining puberty, the calculation results in +900,000 generations.</p> + +<p>Further back we cannot go. We do not +know of any Vertebrate remains from the +Ordovician and Cambrian, which together +represent 6,700,000 years, enough for at least +half as many generations of Prochordate +creatures. The pre-Cambrian or Laurentian +epoch lies quite beyond the reach of calculation, +nor have we any trustworthy fossil +remains of living matter from these strata, to +which, however, Haeckel and others refer the +first beginnings of life.</p> + +<p><span class="pagenum"><a name="Page_154" id="Page_154">[Pg 154]</a></span></p> + +<p>All the above calculations are, of course, +only approximate. What we do know is +the existence of representatives of the stages, +our proofs being the fossils; but when we refer +the origin of the Eotetrapoda, for example, to +the bottom and not somewhere to the middle +of the Coal-measures, we are guessing +merely. Alterations in the levels assumed +for the various stage-representatives will, of +course, alter the result of the number of +generations; but the leading idea, as a +whole, is not thereby upset. The fact +remains that in the Upper Silurian we have +fishes; from the Coal-measures onwards, fishes +and Amphibia; since the Permian, fishes, +Amphibia, and reptiles; since the end of the +Trias these three classes and the Mammalia; +and lastly, at least since the Plistocene, man +himself. If Evolution is true at all, the +transformation from early fish-like creatures +to man has come about within these epochs. +Being able to assign a time of duration to +each of them, with an approximate total of<span class="pagenum"><a name="Page_155" id="Page_155">[Pg 155]</a></span> +21,000,000 years, we are also able to put +the whole ancestral series to a test by expressing +each great stage in generations. The +result is very satisfactory. The whole enormous +stretch from the lowest fish-like creatures +to man has been resolved into more +than 5,000,000 successive generations, and +each of these means a little step forwards in +onward Evolution.</p> + +<p>Nothing is to be gained for the understanding +of our problem of Evolution if we +multiply this enormous number of generations +by ten or any other multiple. We +are not able to conceive changes so small +as those which necessarily have existed +between Pithecanthropus and man if the +whole striking difference is analysed into +17,000 steps. Every one of these stages in +the modifications of the muscles, the skeletal +framework, increase of brain, shortening of +the trunk, lengthening of the legs, improvement +of the hands, loss of the hairy coat, etc., +is truly microscopical, imperceptible, just as<span class="pagenum"><a name="Page_156" id="Page_156">[Pg 156]</a></span> +the Evolutionist imagines the whole process +to have been. Again, where is the difficulty +implied by the change from an air-breathing, +in many structural points half-amphibian, fish +into a primitive land-crawling four-footed +creature, if we are allowed to resolve the +transformation into 1,000,000 stages? So far +from there being any difficulty, rather does it +appear questionable if so many infinitely small +changes have been necessary to bring about +this result.</p> + +<p>One thousand years make apparently no +difference in the evolution of animals, nor +does one second change the aspect of the +hands on the face of a clock, nor did Julius +Cæsar's commission of scientific men appreciate +the error of about eleven minutes in +the length of the year beyond its real value; +but now the Russians are, owing to this +neglect, nearly two weeks behind the civilized +nations.</p> + + +<p class="center">THE END.<br /> + +<small>BILLING AND SONS, PRINTERS, GUILDFORD.</small></p> + +<p><span class="pagenum"><a name="Page_157" id="Page_157">[Pg 157]</a></span></p> +<hr class="chap"/> +<div class="chapter-beginning"/> +<p class="center">By PROFESSOR ERNST HAECKEL</p> + +<p class="center"><big>MONISM</big>;<br /> +<small>OR</small>,<br /> +The Confession of Faith of a Man of Science.</p> + +<p class="center"> Translated from the German by J. D. F. GILCHRIST.</p> + +<p class="center"><i>Crown 8vo., cloth. Price 1s. 6d. net.</i> +</p> + +<p>'We may readily admit that Professor Haeckel has stated his case +with the clearness and courage which we should expect of him, and +that his lecture may be regarded as a fair and authoritative statement +of the views now held by a large number of scientifically educated +people.'—<i>Times.</i></p> + +<p>'The Monism, which is the substance of his faith, is thus defined by +him: "Our conviction that there lives one spirit in all things, and that +the whole cognizable world is constituted, and has been developed, in +accordance with one common fundamental law." As the confession of +a distinguished man of science, this little work deserves to be read.'—<i>North +British Daily Mail.</i></p> + +<p>'This "Confession of Faith" was delivered by the great German +scientist, its author, as an extemporaneous address at Altenburg rather +more than two years ago. There are, no doubt, a large number of +English readers who will welcome a translation, for this "connecting of +religion and science" has long troubled many earnest students of +modern science.'—<i>Publisher's Circular.</i></p> + +<p>'This is a little book of great daring, an example of the wild speculative +flights of one of the very ablest and greatest of our contemporary +men of science.'—<i>Aberdeen Free Press.</i></p> + +<p>'The address, whatever we may think of its conclusions, is, however, +most interesting reading, and is admirably done into English by the +translator.'—<i>Literary World.</i></p> + + +<p class="center">LONDON: ADAM & CHARLES BLACK, SOHO SQUARE.</p> + +<p><span class="pagenum"><a name="Page_158" id="Page_158">[Pg 158]</a></span></p> +<hr class="tb"/> + +<p class="center"> <i>Demy 8vo., price 7s. 6d. net.</i></p> + +<p class="center"><big>SOURCES OF THE APOSTOLIC CANONS.</big></p> + +<p class="center"> <i>With a Treatise on the Origin of the Readership and other Lower Orders.</i></p> + +<p class="center"> By Professor ADOLF HARNACK.</p> + +<p class="center"> Translated by LEONARD A. WHEATLEY.</p> + +<p class="center"> <i>With an Introductory Essay on the Organization of the Early Church + and the Evolution of the Reader.</i></p> + +<p class="center"> By the Rev. <span class="smcap">John Owen</span>, Author of 'Evenings with the Skeptics.' +</p> + +<p>'Dr. Adolf Harnack is at the present time undoubtedly the leading liberal +authority in Germany on matters connected with early Christian history.'—<i>The +Times.</i></p> + +<p>'Those who are interested in early Church history know how to prize anything +from the pen of Prof. Harnack. They will not be disappointed with the present +paper, in which, with his accustomed learning and acute criticism, he annotates +and comments upon the fragments of primitive church law which partly form the +basis of the Apostolic Canons.'—<i>British Weekly.</i></p> + +<p>'The wide circulation of this volume would be of the happiest augury for a +more scientific and worthy conception of the organization of the primitive +Church.'—Dr. <span class="smcap">Marcus Dods</span> in <i>The Bookman</i>.</p> + + +<hr class="tb"/> +<p class="center"> <i>Crown 8vo., cloth, price 1s. 6d. net.</i></p> + +<p class="center"><big>CHRISTIANITY AND HISTORY.</big></p> + +<p class="center"> By ADOLF HARNACK.</p> + +<p class="center"> Translated, with the Author's sanction, by THOMAS BAILEY + SAUNDERS, with an Introductory Note. +</p> + +<p>'It is highly interesting and full of thought. The short introductory note with +which Mr. Saunders prefaces it is valuable for its information and excellent in its +tone.'—<i>Athenæum.</i></p> + +<p>'A singularly able exposition and defence of Christianity, as seen in the newer +light, by one of the most learned and acute "evangelical" critics of Germany. +The essay is a masterly one.'—<i>Glasgow Herald.</i></p> + +<p>' ... We hope the lecture will be widely read.'—<i>Primitive Methodist +Quarterly Review.</i></p> + +<p>'The lecture itself is weighty in its every word, and should be read and re-read +by those desiring to have in a nutshell the central positions of modern Christianity.'—<i>Christian +World.</i></p> + +<p class="center">LONDON: ADAM & CHARLES BLACK, SOHO SQUARE.</p> +<p><span class="pagenum"><a name="Page_159" id="Page_159">[Pg 159]</a></span></p> +<hr class="tb"/> + +<p class="center"> <i>Third Edition. Crown 8vo., cloth, price 5s.</i></p> + +<p class="center"><big>SKETCH OF THE HISTORY OF ISRAEL AND JUDAH.</big></p> + +<p class="center"> By J. WELLHAUSEN,<br /> +<small>PROFESSOR AT MARBURG.</small> +</p> + +<p>'This work is now issued for the third time as an independent +treatise. It admirably epitomizes the subject, and exhibits on almost +every page evidences of Professor Wellhausen's profound study.'—<i>Publishers' +Circular.</i></p> + +<p>'We would only say that those who differ from his critical views +will yet do well to study them, and to read this history in which +he applies them. Its separate publication, in a handy form and at +a moderate price, makes it generally accessible.'—<i>North British +Daily Mail.</i></p> + +<p>'The publication in a separate form of Professor Wellhausen's +article in the "Encyclopædia Britannica" on "Israel" will be very +warmly welcomed by many readers.'—<i>Manchester Guardian.</i></p> + +<p>'We are very glad to welcome an edition of Professor Wellhausen's +"Sketch of the History of Israel and Judah" in a convenient +and handy form. This is the first time it has appeared in +a separate form. It is already known to students; it ought now +to become popular. It is based on the learned author's studies in +Hebrew literature and history, and, though not controversial in form, +it differs totally from orthodox presentations of the subject.'—<i>Westminster +Review.</i></p> + +<p>'A sketch which has created such widespread and profound +interest as this could not be kept in the pages of a voluminous +encyclopædia. Wellhausen's words necessarily have exceptional +importance, even in the esteem of those who differ from him <i>toto +cœlo</i>.'—<i>Baptist Magazine.</i></p> + +<p>'The profound scholarship of the author does not elevate his +writing above the interest of the general reader, and a vivid idea +of the involved Jewish history is obtainable from this volume.'—<i>Christian +Advocate.</i></p> + +<p class="center">LONDON: ADAM & CHARLES BLACK, SOHO SQUARE.</p> +<p><span class="pagenum"><a name="Page_160" id="Page_160">[Pg 160]</a></span></p> +<hr class="tb"/> +<p class="center"> <i>Demy 8vo., boards, price 3s. 6d. net.</i></p> + +<p class="center"><big>A CLASSIFICATION OF VERTEBRATA,</big><br /> + RECENT AND EXTINCT.</p> + +<p class="center"> With Diagnoses and Definitions, a Chapter on Geographical + Distribution, and an Etymological Index.</p> + +<p class="center"> By HANS GADOW, M.A., <span class="smcap">Ph.D.</span>, F.R.S.,</p> + +<p class="center"><small>STRICKLAND CURATOR AND LECTURER ON ZOOLOGY TO THE UNIVERSITY, + CAMBRIDGE.</small> +</p> + +<p>'At the end of his work Dr. Gadow adds a useful chapter on the geographical +distribution of the Vertebrata, with a table showing the approximate number of +the known recent species. He also gives a fanciful though striking calculation +to show how some groups are still in the ascendant, while others are distinctly +declining. The little volume is indeed a welcome addition to the biological +student's library, and it deserves the wide circulation which its author's eminence +is likely to ensure for it.'—<i>Natural Science.</i></p> + +<p>'It is a book, it need hardly be said, for the student; it is simply a list of the +principal sub-divisions of backboned animals, with just as much definition as is +needed. It may be regarded as an exceedingly concentrated extract of a full +text-book of the vertebrates.'—<i>Daily Chronicle.</i></p> + +<p class="center">LONDON: ADAM & CHARLES BLACK, SOHO SQUARE.</p> +<hr class="tb"/> + + +<p class="center"> <i>Demy 8vo., cloth, price 21s.</i></p> + +<p class="center"><big>IN NORTHERN SPAIN.</big></p> + +<p class="center"> By Dr. HANS GADOW, M.A., <span class="smcap">Ph.D.</span>, F.R.S.</p> + +<p class="center"> <i>Containing Map and 89 Illustrations.</i> +</p> + +<p>'Some years back "Wild Spain," one of the best books of its kind, made you +desirous of knowing more of the country. And Hans Gadow has deepened this +feeling in his excellent volume "In Northern Spain," and that to an enormous +extent. Dwelling at inn or farm, or in their own tent, they saw the country as +it has been seen but rarely, and they came to know the inhabitants as they can +be known in no other fashion.'—<i>Black and White.</i></p> + +<p>'To persons visiting the provinces with which the author deals, this book will +be invaluable, and will do more to point their attention to objects of interest than +existing guide-books of Spain, most of which are out of date.'—<i>The Field.</i></p> + +<p>'About the best book of European travel that has appeared these many +years.'—<i>Literary World.</i></p> + +<p class="center">LONDON: ADAM & CHARLES BLACK, SOHO SQUARE.</p> + + +<div class="footnotes"><h3>FOOTNOTES:</h3> + +<div class="footnote"> + +<p><a name="Footnote_1_1" id="Footnote_1_1"></a><a href="#FNanchor_1_1"><span class="label">[1]</span></a> See note,p.<a name="FNanchor_40" id="FNanchor_40"></a><a href="#Footnote_40">80.</a> </p> + +<p><a name="Footnote_2_2" id="Footnote_2_2"></a><a href="#FNanchor_2_2"><span class="label">[2]</span></a> See note, p.<a name="FNanchor_41" id="FNanchor_41"></a><a href="#Footnote_41">89.</a></p> + +<p><a name="Footnote_3_3" id="Footnote_3_3"></a><a href="#FNanchor_3_3"><span class="label">[3]</span></a> +See notes, p. <a name="FNanchor_42" id="FNanchor_42"></a><a href="#Footnote_42">102</a>, <a name="FNanchor_43" id="FNanchor_43"></a><a href="#Footnote_43">106</a>. </p> + +<p><a name="Footnote_5_5" id="Footnote_5_5"></a><a href="#FNanchor_5_5"><span class="label">[5]</span></a> +See note, p. <a name="FNanchor_44" id="FNanchor_44"></a><a href="#Footnote_44">80.</a> </p> + +<p><a name="Footnote_6_6" id="Footnote_6_6"></a><a href="#FNanchor_6_6"><span class="label">[6]</span></a> <i>Perfect</i>, in the sense of highest stage of evolution, may +seem a <i>petitio principii</i>. Leaving aside the consideration +that no living creature is absolutely perfect, in the sense that +its organization cannot become more efficient or proficient, +we have here to deal with relative perfection of the whole +organization. A fish or a snake is in its way more specialized +than a mammal; but specialization does not necessarily +mean height of development: it generally means life in a +comparatively narrow groove. The acts of giving birth and +nourishing the young with the mother's milk is a much +higher stage than the act of laying eggs and letting them +run their chance. The development of a hairy coat goes +along with heightened temperature of the blood, subsequent +greater independence of the surrounding temperature, and +increased steady activity of the brain and other nerve-centres. +The brain of the Mammalia, in its minute structure, +is much more complex. This rule applies to some of +the principal sense organs, chiefly the nose and the ear. +The skeleton, not so much as a whole as in the various bones +and joints, is more neatly finished, and built up more in +conformity with 'scientific principles,' than is the case even +with birds, in spite of their marvellous specialization. The +same is the case with the vascular system, notably the heart +and the veins, and with the excretory organs. In all of these +many imperfections, still to be found in the other classes, +have been corrected in Mammalia. The Primates take an +easy first by their hands, and among them the apes and man +himself by their brains.</p> + +<p><a name="Footnote_7_7" id="Footnote_7_7"></a><a href="#FNanchor_7_7"><span class="label">[7]</span></a> 'Die menschenähnlichen Affen und ihre Organisation +im Vergleich zur menschlichen.' 1883.</p> + +<p><a name="Footnote_8_8" id="Footnote_8_8"></a><a href="#FNanchor_8_8"><span class="label">[8]</span></a> G. Schwalbe, 'In wiefern ist die menschliche Ohrmuschel ein +rudimentäres Organ?'—In what Respects is the Human Outer Ear a +Rudimentary Organ? (<i>Archiv f. Anatomie und Physiologie</i>, 1889).</p> + +<p><a name="Footnote_9_9" id="Footnote_9_9"></a><a href="#FNanchor_9_9"><span class="label">[9]</span></a> Wiedersheim, 'Der Bau des Menschen als Zeugniss für +seine Vergangenheit.' Freiburg, 1888. Translated: 'The +Structure of Man an Index to his Past History.' London, +1895.</p> + +<p><a name="Footnote_10_10" id="Footnote_10_10"></a><a href="#FNanchor_10_10"><span class="label">[10]</span></a> <i>Pithecanthropus erectus.</i> 'Eine menschenähnliche +Uebergangsform aus Java' ('A Human-like Transitional +Form'). Batavia, 1894.</p> + +<p><a name="Footnote_11_11" id="Footnote_11_11"></a><a href="#FNanchor_11_11"><span class="label">[11]</span></a> On the day after the delivery of this address Dr. Dubois +exhibited the cranium of Pithecanthropus, from which he had +removed the stony matrix which filled the inside, in order to +examine the impression left by the cerebral convolutions. +He was able to show that they also are very human, and +more highly developed than those of the recent apes.</p> + +<p><a name="Footnote_12_12" id="Footnote_12_12"></a><a href="#FNanchor_12_12"><span class="label">[12]</span></a> L. Manouvier: 'Deuxième étude sur le Pithecanthropus erectus +comme précurseur présumé de l'homme.' (<i>Bulletins de la Soc. +d'Anthropologie de Paris</i>, 1895.)</p> + +<p><a name="Footnote_13_13" id="Footnote_13_13"></a><a href="#FNanchor_13_13"><span class="label">[13]</span></a> +See notes, p. <a name="FNanchor_45" id="FNanchor_45"></a><a href="#Footnote_45">93.</a> </p> + +<p><a name="Footnote_14_14" id="Footnote_14_14"></a><a href="#FNanchor_14_14"><span class="label">[14]</span></a> +See notes, p. <a name="FNanchor_46" id="FNanchor_46"></a><a href="#Footnote_46">87.</a> </p> + +<p><a name="Footnote_15_15" id="Footnote_15_15"></a><a href="#FNanchor_15_15"><span class="label">[15]</span></a> +</p> + +<blockquote> + +<p><span class="smcap">F. Ameghino</span>: 'Contribucion al conocimiento de los +mamíferos de la república Argentina.' In <i>Actas de +la Academia nacional de Sciencias en Cordoba</i>, +1889.—Another article in <i>Revista Argentina de Historia +natural</i>. Buenos Aires, 1891. +</p> +<p> +<span class="smcap">A. Gaudry</span>: 'Animaux fossiles et géologie de l'Attique.' +1862.—'Le Dryopithèque.' <i>Mém. Soc. géol. de +France</i>: 'Paléontologie.' 1890. +</p> +<p> +<span class="smcap">O. Marsh</span>: 'Introduction and Succession of Vertebrate +Life in America.' Address, Amer. Assoc. Adv. Sci., +Nashville, 1887. +</p> +<p> +<span class="smcap">H. F. Osborn</span>: 'The Rise of the Mammalia in North +America.' Address, Amer. Assoc. Adv. Sci., Madison, +1893. +</p> +<p> +<span class="smcap">L. Ruetimeyer</span>: 'Ueber die Herkunft unserer Thierwelt,' +Basel, 1867. +</p> +<p> +<span class="smcap">C. S. Forsyth Major</span>: 'Fossil Monkeys from Madagascar.' +<i>Geological Magazine</i>, 1896. +</p> +<p> +<span class="smcap">M. Schlosser</span>: 'Ueber die Beziehungen der ausgestorbenen +Saeugethierfaunen und ihr Verhaeltniss zur Saeugethierfauna +der Gegenwart.' Biolog. Centralblatt, 1888.</p> +</blockquote> + +<p><a name="Footnote_16_16" id="Footnote_16_16"></a><a href="#FNanchor_16_16"><span class="label">[161</span></a> +See notes, p. <a name="FNanchor_47" id="FNanchor_47"></a><a href="#Footnote_47">102</a>, <a name="FNanchor_48" id="FNanchor_48"></a><a href="#Footnote_48">106</a>. </p> + +<p><a name="Footnote_17_17" id="Footnote_17_17"></a><a href="#FNanchor_17_17"><span class="label">[171</span></a> +See note, p. <a name="FNanchor_49" id="FNanchor_49"></a><a href="#Footnote_49">97</a>.</p> + +<p><a name="Footnote_18_18" id="Footnote_18_18"></a><a href="#FNanchor_18_18"><span class="label">[18]</span></a> Wilhelm Bischoff of Munich: works on the history +of the development of the rabbit, dog, guinea-pig, roe-deer. +1840-1854.</p> + +<p><a name="Footnote_19_19" id="Footnote_19_19"></a><a href="#FNanchor_19_19"><span class="label">[191</span></a> +See note, p. <a name="FNanchor_50" id="FNanchor_50"></a><a href="#Footnote_50">96</a>. </p> + +<p><a name="Footnote_20_20" id="Footnote_20_20"></a><a href="#FNanchor_20_20"><span class="label">[20]</span></a> 'Ueber die Entwicklung der einfachen Ascidien,' Mém. +Acad. St. Petersbourg, vii. ser., tome x. (1866). Other +papers in 'Archiv f. Mikroskop. Anatomie,' vii. (1871); xiii. +(1877).</p> + +<p><a name="Footnote_21_21" id="Footnote_21_21"></a><a href="#FNanchor_21_21"><span class="label">[21]</span></a> +See notes, p. <a name="FNanchor_51" id="FNanchor_51"></a><a href="#Footnote_51">102</a>, <a name="FNanchor_52" id="FNanchor_52"></a><a href="#Footnote_52">106</a>.</p> + +<p><a name="Footnote_22_22" id="Footnote_22_22"></a><a href="#FNanchor_22_22"><span class="label">[22]</span></a> Similar conditions seem to have prevailed among the +Proreptilia; but in those of their descendants which have +specialized into Reptiles and Birds the basi-occipital element +becomes more and more predominant in that formation +which ultimately leads to the apparently single condyle. +Hence it is misleading to divide the Tetrapoda into the two +main groups of Amphi-and Mono-condylia, and therefrom +to conclude that the two-condyled Mammalia are more +closely related to the likewise amphicondylous Amphibia +than to the so-called monocondylous Reptiles.</p> + +<p><a name="Footnote_23_23" id="Footnote_23_23"></a><a href="#FNanchor_23_23"><span class="label">[23]</span></a> 'Ergebnisse naturwissenschaftlicher Forschungen auf +Ceylon,' vols. 4 and 5. (With an atlas of 84 plates; 1893.)</p> + +<p><a name="Footnote_24_24" id="Footnote_24_24"></a><a href="#FNanchor_24_24"><span class="label">[24]</span></a> 'Principles of Biology': 'The Factors of Organic Evolution'; +'The Inadequacy of Natural Selection.'</p> + +<p><a name="Footnote_25_25" id="Footnote_25_25"></a><a href="#FNanchor_25_25"><span class="label">[25]</span></a> Abridged from Haeckel's 'Systematische Phylogenie +der Vertebraten,' § 14.</p> + +<p><a name="Footnote_26_26" id="Footnote_26_26"></a><a href="#FNanchor_26_26"><span class="label">[26]</span></a> That this great work is now comparatively rare, although +still in the second-hand market, may perhaps be urged in +excuse of the fact of so many attempts made by many authors, +both professional and amateur, to find fault with or to +explain the principles of adaptation, variation, heredity, +cænogenesis, phylogeny, etc., in complete ignorance that +all these and many more fundamental questions were fully +discussed more than thirty years ago in the 'Generelle Morphologie.'</p> + +<p><a name="Footnote_27_27" id="Footnote_27_27"></a><a href="#FNanchor_27_27"><span class="label">[27]</span></a> James Croll: 'On Geological Time, and the Probable +Date of the Glacial and Upper Miocene Period,' <i>Philos. +Magazine</i>, xxxv., 1868, pp. 363-384; xxxvi., pp. 141-154; +362-386.</p> + +<p><a name="Footnote_28_28" id="Footnote_28_28"></a><a href="#FNanchor_28_28"><span class="label">[28]</span></a> William Thomson: 'On the Secular Cooling of the +Earth,' <i>Transact. R. S. Edinb.</i>, xxiii., 1864, pp. 157-169.</p> + +<p><a name="Footnote_29_29" id="Footnote_29_29"></a><a href="#FNanchor_29_29"><span class="label">[29]</span></a> 'Geological Time as indicated by the Sedimentary +Rocks of North America.' <i>Proc. Amer. Assoc. Adv. Sci.</i>, +xlii., 1893, pp. 129-169.</p> + +<p><a name="Footnote_30_30" id="Footnote_30_30"></a><a href="#FNanchor_30_30"><span class="label">[30]</span></a> Henry Shaler Williams, 'Geological Biology.' New +York, 1895.</p> +</div> +</div> + +<p class= "transnote"> +Transcriber's Notes<br /> + + Variations in spelling, punctuation and hyphenation have been retained + except in obvious cases of typographical errors. + Inconsistent hyphenation and spelling are as in the original. + The layout of the chart Ancestral Tree of The Mammalia has been changed + from the original to enhance clarity, the essential relationships have + been preserved. + The second reference to footnote 3, in the same paragraph as the first, + has been left blind as it is redundant. +</p> + + + + + + + + +<pre> + + + + + +End of the Project Gutenberg EBook of The Last Link, by Ernst Haeckel + +*** END OF THIS PROJECT GUTENBERG EBOOK THE LAST LINK *** + +***** This file should be named 44541-h.htm or 44541-h.zip ***** +This and all associated files of various formats will be found in: + http://www.gutenberg.org/4/4/5/4/44541/ + +Produced by Chris Curnow, Les Galloway and the Online +Distributed Proofreading Team at http://www.pgdp.net (This +file was produced from images generously made available +by The Internet Archive) + + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. 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You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: The Last Link + Our Present Knowledge of the Descent of Man + +Author: Ernst Haeckel + +Commentator: Hans Gadow + +Release Date: December 29, 2013 [EBook #44541] + +Language: English + +Character set encoding: ASCII + +*** START OF THIS PROJECT GUTENBERG EBOOK THE LAST LINK *** + + + + +Produced by Chris Curnow, Les Galloway and the Online +Distributed Proofreading Team at http://www.pgdp.net (This +file was produced from images generously made available +by The Internet Archive) + + + + + + + THE LAST LINK + + OUR PRESENT KNOWLEDGE OF THE + DESCENT OF MAN + + BY + + ERNST HAECKEL + (JENA) + + WITH NOTES AND BIOGRAPHICAL SKETCHES + + BY + + HANS GADOW, F.R.S. + (CAMBRIDGE) + + + LONDON + ADAM AND CHARLES BLACK + 1898 + + + +CONTENTS + + + PAGE + THE LAST LINK + + INTRODUCTORY 1 + + COMPARATIVE ANATOMY 8 + + PALAEONTOLOGY 20 + + OTHER EVIDENCE 42 + + STAGES RECAPITULATED 47 + + BIOGRAPHICAL SKETCHES: + + LAMARCK, SAINT-HILAIRE, CUVIER, BAER, + MUELLER, VIRCHOW, COPE, KOELLIKER, GEGENBAUR, + HAECKEL 80 + + THEORY OF CELLS 115 + + FACTORS OF EVOLUTION 117 + + GEOLOGICAL TIME AND EVOLUTION 135 + + + + NOTE + + +The address I delivered on August 26 at the Fourth International +Congress of Zoology at Cambridge, 'On our Present Knowledge of the +Descent of Man,' has, I find, from the high significance of the theme +and the general importance of the questions connected with it, excited +much interest, and has led to requests for its publication. Hence this +volume, edited by my friend Dr. H. Gadow, my pupil in earlier days, +who has not only revised the text, but has also enriched it by many +valuable additions and notes. + + ERNST HAECKEL. + +_Jena, December, 1898._ + + + + + THE LAST LINK + + +At the end of the nineteenth century, the age of 'natural science,' the +department of knowledge that has made most progress is zoology. From +zoology has arisen the study of transformism, which now dominates the +whole of biology. Lamarck[1] laid its foundation in 1809, and forty +years ago Charles Darwin obtained for it a recognition which is now +universal. It is not my task to repeat the well-known principles of +Darwinism. I am not concerned to explain the scientific value of the +whole theory of descent. The whole of our biological study is pervaded +by it. No general problem in zoology and botany, in anatomy and +physiology, can be discussed without the question arising, How has this +problem originated? What are the real causes of its development? + + [1] See note, p. 80. + +This question was almost unknown seventy years ago, when Charles +Darwin, the great reformer of biology, began his academical career at +Cambridge as a student of theology. In the same year, 1828, Carl Ernst +von Baer[2] published in Germany his classical work on the embryology +of animals, the first successful attempt to elucidate by 'observation +and reflection' the mysterious origin of the animal body from the +egg, and to explain in every respect the 'history of the growing +individuality.' Darwin at that time had no knowledge of this great +advance, and he could not divine that forty years later embryology +would be one of the strongest supports of his own life's work--of that +very theory of transformism which, founded by Lamarck in the year of +Darwin's birth, was accepted with enthusiasm by Charles's grandfather +Erasmus. There is no doubt that of all the celebrated naturalists of +the nineteenth century Darwin achieved the greatest success, and we +should be justified in designating the last forty years as the Age of +Darwin. + + [2] See note, p. 89. + +In searching for the causes of this unexampled success, we must clearly +separate three sets of considerations: first, the comprehensive reform +of Lamarck's transformism, and its firm establishment by the many +arguments drawn from modern biology; secondly, the construction of the +new theory of selection, as established by Darwin, and independently +by Alfred Wallace (a theory called Darwinism in the proper sense); +thirdly, the deduction of anthropogeny, that most important conclusion +of the theory of descent, the value of which far surpasses all the +other truths in evolution. + +It is the third point of Darwin's theory that I shall discuss here; and +I shall discuss it chiefly with the intention of examining critically +the evidence and the different conclusions which at present represent +our scientific knowledge of the descent of man and of the different +stages of his animal pedigree. + +It is now generally admitted that this problem is the most important +of all biological questions. Huxley was right when in 1863 he called +it the question of questions for mankind. The problem which underlies +all others, and is more deeply interesting than any other, is as +to the place which man occupies in nature and his relations to the +universe of things. 'Whence our race has come; what are the limits of +our power over nature, and of nature's power over us; to what goal are +we tending--these are the problems which present themselves anew and +with undiminished interest to every man born into the world.' This +impressive view was explained by Huxley thirty-five years ago in his +three celebrated essays on 'Evidence as to Man's Place in Nature.' The +first is entitled 'On the Natural History of the Man-like Apes'; the +second, 'On the Relations of Man to the Lower Animals'; the third, 'On +some Fossil Remains of Man.' Darwin himself felt the burden of these +problems as much as Huxley; but in his chief work, 'On the Origin of +Species,' in 1859, he had purposely only just touched them, suggesting +that the theory of descent would shed light upon the origin of man and +his history. Twelve years later, in his celebrated work on 'The Descent +of Man, and Selection in Relation to Sex,' Darwin discussed fully and +ingeniously all the different sides of this 'question of questions' +from the morphological, historical, physiological, and psychological +points of view. As early as 1866 I myself had applied in the _Generelle +Morphologie der Organismen_ the theory of transformism to anthropology, +and had shown that the fundamental law of biogeny claims the same +value for man as for all the other animals. The intimate causal +connection between ontogeny and phylogeny, between the development of +the individual and the history of its ancestors, enables us to gain +a safe and certain knowledge of our ancestral series. I had at that +time distinguished in this series ten chief degrees of vertebrate +organization. I attributed the highest importance to the logical +connection of anthropogeny with transformism. If the latter be true, +the truth of the former is absolute. 'Our theory that man is descended +from lower vertebrates, and immediately from apes or primates, is a +case of special _deduction_ which follows with absolute certainty from +the general _induction_ of the theory of descent.' The full proof and +detailed explanation of this view was afterwards given in my 'History +of Natural Creation,' and especially in my 'Anthropogeny.'[3] Lastly, +it has received an ample scientific and critical foundation in the +third part of my 'Systematic Phylogeny.'[3] + + [3] See notes, pp. 102, 106 + +During the forty years which have elapsed since Darwin's first +publication of his theories an enormous literature, discussing the +_general problems_ of transformism as well as its special application +to man, has been published. In spite of the wide divergence of the +different views, all agree in one main point: the natural development +of man cannot be separated from general transformism. There are only +two possibilities. Either all the various species of animals and +plants have been created independently by supernatural forces (and +in this case the creation of man also is a miracle); or the species +have been produced in a natural way by transmutation, by adaptation +and progressive heredity (and in this case man also is descended from +other vertebrates, and immediately from a series of primates). We are +absolutely convinced that only the latter theory is fully scientific. +To prove its truth, we have to examine critically the strength of the +different arguments claimed for it. + + + + + I. + + +First, we have to consider the relative place which comparative +anatomy concedes to man in the 'natural system' of animals, for the +true value of our 'natural classification' is based upon its meaning +as a pedigree. All the minor and major groups of the system--the +classes, legions, orders, families, genera, and species--are only +different branches of the same pedigree. For man himself, his place +in the pedigree has been fixed since Lamarck,[4] in 1801, defined the +group of vertebrates. The most perfect[5] of these are the Mammalia; +and at the head of this class stands the order of Primates, in which +Linnaeus, in 1735, united four 'genera'--Homo, Simia, Lemur, and +Vespertilio. If we exclude the last-named, the Chiroptera of modern +zoology, there remain three natural groups of Primates--the Lemures, +the Simiae, and the Anthropi or Hominidae. This is the classification of +the majority of zoologists; but if we compare man with the two chief +groups of monkeys--the Eastern monkeys (or Catarrhinae) and the Western +or American monkeys (Platyrrhinae)--there can be no doubt that the +former group is much more closely related to man than is the latter. +In the natural order of the Catarrhinae we find united a long series +of lower and higher forms. The lowest, the Cynopitheci, appear still +closely related to the Platyrrhinae and to the Lemures; while, on the +other hand, the tailless apes (Anthropomorphae) approach man through +their higher organization. Hence one of our best authorities on the +Primates, Robert Hartmann,[6] proposed to subdivide the whole order of +the Simiae into three groups: (1) Primarii, man together with the other +Anthropomorphae, or tailless apes; (2) Simiae, all the other monkeys; (3) +Prosimiae, or Lemurs. This arrangement has received strong support from +the interesting discovery by Selenka that the peculiar placentation +of the human embryo is the same as in the great apes, and different +from that of all the other monkeys. Our choice between these different +classifications of Primates is best determined by the important thesis +of Huxley, in which, in 1863, he carried out a most careful and +critical comparison of all the anatomical gradations within this order. +In my opinion, this ingenious thesis--which I have called the Huxleyan +Law, or the 'Pithecometra-thesis of Huxley'--is of the utmost value. +It runs as follows: 'Thus, whatever system of organs be studied, the +comparison of their modifications in the ape-series leads to one and +the same result--that the structural differences which separate man +from the gorilla and the chimpanzee are not so great as those which +separate the gorilla from the lower apes.' If we accept the Huxleyan +law without prejudice, and apply it to the natural classification of +the Primates, we must concede that man's place is within the order +of the Simiae. On examining this relation with care, and judging +with logical persistence, we may even go a step further. Instead of +the wider conception of 'Simiae,' we must use the restricted term of +Catarrhinae, and our Pithecometra-thesis has then to be formulated +as follows: _The comparative anatomy of all organs of the group of +Catarrhine Simiae leads to the result that the morphological differences +between man and the great apes are not so great as are those between +the man-like apes and the lowest Catarrhinae_. In fact, it is very +difficult to show why man should not be classed with the large apes in +the same zoological family. We all know a man from an ape; but it is +quite another thing to find differences which are absolute and not of +degree only. Speaking generally, we may say that man alone combines the +four following features: (1) Erect walk; (2) extremities differentiated +accordingly; (3) articulate speech; (4) higher reasoning power. Speech +and reason are obviously relative distinctions only--the direct result +of more brains and more brain-power, the so-called mental faculties. +The erect walk is not an absolutely distinguishing characteristic: the +large apes likewise walk on their feet only, supporting their bodies +by touching the ground with the backs of their hands--in fact, with +their knuckles--and this is a mode of progression very different from +that of the tailed monkeys, which walk upon the palms of their hands. +There are, however, two obvious differences in the development of the +muscles. In man alone the gastrocnemius and the soleus muscle are thick +enough to form the calf of the leg, and the glutaeus maximus is enlarged +into the buttocks. A fourth glutaeal muscle occurs occasionally in +man, while it is constantly present in apes as the so-called musculus +scansorius. Concerning the muscles of the whole body, we cannot do +better than quote Testut's summary: 'The mass of recorded observations +upon the muscular anomalies in man is so great, and the agreement of +many of these with the condition normal in apes is so marked, that the +gap which usually separates the muscular system of man from that of the +apes appears to be completely bridged over.' + + [4] See note, p. 80. + + [5] _Perfect_, in the sense of highest stage of evolution, may seem a + _petitio principii_. Leaving aside the consideration that no living + creature is absolutely perfect, in the sense that its organization + cannot become more efficient or proficient, we have here to deal with + relative perfection of the whole organization. A fish or a snake is in + its way more specialized than a mammal; but specialization does not + necessarily mean height of development: it generally means life in a + comparatively narrow groove. The acts of giving birth and nourishing + the young with the mother's milk is a much higher stage than the act + of laying eggs and letting them run their chance. The development of + a hairy coat goes along with heightened temperature of the blood, + subsequent greater independence of the surrounding temperature, and + increased steady activity of the brain and other nerve-centres. The + brain of the Mammalia, in its minute structure, is much more complex. + This rule applies to some of the principal sense organs, chiefly the + nose and the ear. The skeleton, not so much as a whole as in the + various bones and joints, is more neatly finished, and built up more + in conformity with 'scientific principles,' than is the case even with + birds, in spite of their marvellous specialization. The same is the + case with the vascular system, notably the heart and the veins, and + with the excretory organs. In all of these many imperfections, still + to be found in the other classes, have been corrected in Mammalia. The + Primates take an easy first by their hands, and among them the apes and + man himself by their brains. + + [6] 'Die menschenaehnlichen Affen und ihre Organisation im Vergleich zur + menschlichen.' 1883. + +There are, for example, the muscles of the ear. In most people the +majority, or even all of them, are no longer movable at will, while in +the apes they are still in use. The important point, however, is that +these muscles are still present in man, although often in a reduced +condition. They are the following: (1) Musculus auricularis anterior +or attrahens auris, which is frequently much reduced and no longer +reaches the ear at all, being then absolutely useless; (2) Musculus +auricularis superior or attollens auris, more constant than the former; +(3) Musculus auricularis posterior or retrahens auris, likewise often +functional. Occasionally smaller slips differentiated from these +three muscles are present, and as so-called intrinsic muscles are +restricted to the ear itself; their function is, or was, that of +curling up or opening the external ear. + +[Illustration: OUTLINES OF THE LEFT EAR OF-- + +1. _Lemur macaco_; 2. _Macacus rhesus_, the Rhesus monkey; 3. +Cercopithecus, a macaque; 4. human embryo of six months; 5. man, with +Darwin's point well retained: the dotted outline is that of the ear of +a baboon; 6. orang-utan (after G. Schwalbe):[7] ^x the original tip of +the ear; 7. human ear with the principal muscles. + + [7] G. Schwalbe, 'In wiefern ist die menschliche Ohrmuschel ein + rudimentaeres Organ?'--In what Respects is the Human Outer Ear a + Rudimentary Organ? (_Archiv f. Anatomie und Physiologie_, 1889).] + +In connection with the ear, I may touch upon another interesting +and most suggestive little feature which is present in many +individuals--namely, 'Darwin's point.' This is the last remnant of the +original tip of the ear, before the outer, upper, and hinder rim became +doubled up or folded in. It is a feature quite useless, and absolutely +impossible of interpretation, excepting as the vestige of such previous +ancestral conditions as are normal in the monkeys. + +In some cases the reduction of muscles has proceeded further in apes +than in man--for example, the muscles of the little toe. Another +instance is afforded by the coccyx or vestige of the tail; this is +still furnished with muscles which are now in man, as well as in +the apes, quite useless, and vary considerably with every sign of +degeneration, most so in the orang-utan. + +Darwin has mentioned the frequent action of the 'snarling muscle,' by +which, in sneering, our upper canine teeth are exposed, like those of a +dog prepared to fight. + +Monkeys and apes possess vocal sacs, especially large in the +orang-utan; survivals of them, although no longer used, persist in man +in the shape of a pair of small diverticula, the pouches of Morgagni, +between the true and the false vocal cords. + +'In the native Australians, the dental formula appears least removed +from the hypothetical original type, for in it are still found complete +rows of splendid teeth, with powerfully-developed canines and molars, +the latter being either uniform, or even increasing in size, as we +proceed backwards, in such a way that the wisdom tooth is the largest +of the series. This is decidedly a pithecoid characteristic which is +always found in apes. The upper incisors of the Malay, apart from their +prognathous disposition, have occasionally a distinctly pithecoid +form, their anterior surface being convex, and their lingual surface +slightly concave. The ancestors of Europeans seem to have had the same +form of teeth, for the oldest existing fragments of skulls from the +Mammoth age (_e.g._, the jaws from La Naulette, in Belgium) reveal +tooth-forms which must be classed with those of the lowest races of +to-day.'[8] + + [8] Wiedersheim, 'Der Bau des Menschen als Zeugniss fuer seine + Vergangenheit.' Freiburg, 1888. Translated: 'The Structure of Man an + Index to his Past History.' London, 1895. + +Now we are able to apply this fundamental Pithecometra-thesis directly +to the classification of the Primates and to the phylogeny of man, +which is intimately connected with it, because in this order, as in +all the other groups of animals, the natural system is the clear +expression of true phylogenetic affinity. Four results follow from our +thesis: (1) The Primates, as the highest legion or order of mammals, +form one natural, monophyletic group. All the Lemures, Simiae, and +Homines descend from one common ancestral form, from a hypothetical +'Archiprimas.' (2) The Lemures are the older and lower of the natural +groups of the Primates; they stand between the oldest Placentalia +(Prochoriata) and the true Simiae. (3) All the Catarrhinae, or Eastern +Simiae, form one natural monophyletic group. Their hypothetical +common ancestor, the Archipithecus, may have descended directly or +indirectly from a branch of the Lemures. (4) Man is descended directly +from one series of extinct Catarrhine ancestors. The more recent +ancestors of this series were tailless anthropoids (similar to the +Anthropopithecus), with five sacral vertebrae. The more remote ancestors +were tailed Cercopitheci, with three or four sacral vertebrae. + +These four theses possess, in my opinion, absolute certainty. +They are independent of all future anatomical, embryological, and +palaeontological discoveries which may possibly throw more light upon +the details of our phyletic anthropogenesis. + + + + + II. + + +The next question is, how the facts of palaeontology agree with these +most important results of comparative anatomy and ontogeny. The fossils +are the true historical 'medals of creation,' the palpable evidence of +the historical succession of all those innumerable organic forms which +have peopled the globe for many millions of years. Here the question +arises, If the known fossil specimens of Mammalia, and particularly +of Primates, give proof of these Pithecometra-theses, do they confirm +directly the descent of man from ape-like creatures? The answer to this +question is, in my opinion, affirmative. + +It is true that the gaps in the palaeontological evidence, here as +elsewhere, are many and keenly felt. In the order of the Primates +they are greater than in many other orders, chiefly because of the +arboreal life of our ancestors. The explanation is very simple. It is +really due to a long chain of favourable coincidences if the skeleton +of a vertebrate, covered as it was with flesh and skin, and containing +still more perishable viscera, is petrified at all. The body may be +devoured by other creatures, and its bones scattered about; or it rots +away and crumbles to pieces. Many animals hide in thick undergrowth +when death approaches them; and, leading an almost entirely arboreal +life, the Primates are especially likely to disappear without being +fossilized. It is only when the body is quickly covered with sand, or +is embedded in suitable lime or silica containing mud, that the process +of petrifaction can come to pass. Even then it is only by great good +luck that we come across such a fossil. Very few countries have been +searched systematically, and the areas that have been searched amount +to little in comparison with the whole surface of the land, even if we +leave out of account the fact that more than two-thirds of the globe +are covered by water. + +These deplorable deficiencies of empirical palaeontology are balanced +on the other side by a growing number of positive facts, which possess +an inestimable value in human phylogeny. The most interesting and most +important of these is the celebrated fossil _Pithecanthropus erectus_, +discovered in Java in 1894 by Dr. Eugene Dubois.[9] Three years ago +this now famous ape-like man provoked an animated discussion at the +third International Zoological Congress at Leyden. I may therefore +be allowed to say a few words as to its scientific significance. +Unfortunately, the fossil remains of this creature are very scanty: the +skull-cap, a femur, and two teeth. It is obviously impossible to form +from these scanty remains a complete and satisfactory reconstruction of +this remarkable Pliocene Primate. + +[9] _Pithecanthropus erectus._ 'Eine menschenaehnliche Uebergangsform +aus Java' ('A Human-like Transitional Form'). Batavia, 1894. + +The more important points are the following: The remains in question +rested upon a conglomerate which lies upon a bed of marine marl and +sand of Pliocene age. Together with the bones of Pithecanthropus were +found those of Stegodon, Leptobos, Rhinoceros, Sus, Felis, Hyaena, +Hippopotamus, Tapir, Elephas, and a gigantic Pangolin. It is remarkable +that the first two of these genera are now extinct, and that neither +hippopotamus nor hyaena exists any longer in the Oriental region. If we +may judge from these fossil remains, the bones of Pithecanthropus are +not younger than the oldest Pleistocene, and probably belong to the +upper Pliocene. The teeth are like those of man. The femur, also, is +very human, but shows some resemblances to that of the gibbons. Its +size, however, indicates an animal which stood when erect not less +than 5 feet 6 inches high. The skull-cap also is very human, but with +very prominent eyebrow ridges, like those of the famous Neanderthal +cranium. It is certainly not that of an idiot. It had an estimated +cranial capacity of about 1,000 cubic centimetres--that is to say, much +more than that of the largest ape, which possesses not more than 600 +c.c. The crania of female Australians and Veddahs measure not more than +1,100, some even less than 1,000 c.c.; but, as these Veddah women stand +only about 4 feet 9 inches high, the computed cranial capacity of the +much taller Pithecanthropus is comparatively very low indeed.[10] + + [10] On the day after the delivery of this address Dr. Dubois exhibited + the cranium of Pithecanthropus, from which he had removed the stony + matrix which filled the inside, in order to examine the impression left + by the cerebral convolutions. He was able to show that they also are + very human, and more highly developed than those of the recent apes. [ + Illustration: The upper figure represents the outlines + of the skull of Pithecanthropus, as restored by Manouvier.[11] The + lower figure shows the comparative size and shape of Pithecanthropus, + the Neanderthal skull, a specimen of the Cro-Magnon race of neolithic + France, and a Young Chimpanzee before the full development of the + supraorbital crests.] + + [11] L. Manouvier: 'Deuxieme etude sur le Pithecanthropus erectus comme + precurseur presume de l'homme.' (_Bulletins de la Soc. d'Anthropologie + de Paris_, 1895.) + +The final result of the long discussion at Leyden was that, of twelve +experts present, three held that the fossil remains belonged to a low +race of man; three declared them to be those of a man-like ape of great +size; the rest maintained that they belonged to an intermediate +form, which directly connected primitive man with the anthropoid +apes. This last view is the right one, and accords with the laws of +logical inference. _Pithecanthropus erectus_ of Dubois is truly a +Pliocene remainder of that famous group of highest Catarrhines which +were the immediate pithecoid ancestors of man. He is, indeed, the +long-searched-for 'missing link,' for which, in 1866, I myself had +proposed the hypothetical genus Pithecanthropus, species Alalus. + +It must, however, be admitted that this opinion is still strongly +combated by some distinguished authorities. At the Leyden Congress it +was attacked by the illustrious pathologist Rudolf Virchow.[12] He, +however, is one of the minority of leading men of science who set +themselves to refute the theory of Evolution in every possible way. For +thirty years he has defended the thesis: 'It is quite certain that man +is not a descendant of apes.' He declares any intermediate form to be +unimaginable save in a dream. + + [12] See Notes, p. 93. + +Virchow went to the Leyden Congress with the set purpose of disproving +that the bones found by Dubois belonged to a creature which linked +together apes and man. First, he maintained that the skull was that +of an ape, while the thigh belonged to man. This insinuation was at +once refuted by the expert palaeontologists, who declared that without +the slightest doubt the bones belonged to one and the same individual. +Next, Virchow explained that certain exostoses or growths observable on +the thigh proved its human nature, since only under careful treatment +the patient could have healed the original injury. Thereupon Professor +Marsh, the celebrated palaeontologist, exhibited a number of thigh-bones +of wild monkeys which showed similar exostoses and had healed without +hospital treatment. As a last argument the Berlin pathologist declared +that the deep constriction behind the upper margin of the orbits +proved that the skull was that of an ape, as such never occurred in +man. It so happened that a few weeks later Professor Nehring of Berlin +demonstrated exactly the same formation on a human prehistoric skull +received by him from Santos, in Brazil. + +Virchow was, in fact, just as unlucky in Leyden in his fight with our +pliocene ancestor as he had been unfortunate in his opinion on the +famous skulls of Neanderthal, Spy, La Naulette, etc., every one of which +he explained as a pathological abnormality. It would be a very curious +coincidence indeed if all these and other fossil human remains were +those of idiots or otherwise abnormal individuals, provided they are +old and low enough in their organization to be of phylogenetic value to +the unbiassed zoologist. + +As the sworn adversary of Evolution, transformism, and Darwinism in +particular, but a believer in the constancy of species, the great and +renowned pathologist has been driven to the incredible contention that +all variations of organic forms are pathological. + +Four years ago, as honorary president of the Anthropological Congress +at Vienna, he attacked Darwinism in the severest manner, and declared +that 'man may be as well descended from the elephant or from the sheep +as from the ape.' Such attacks on the theory of transformism indicate a +failure to understand the principles of the theory of Evolution and to +appreciate the significance of palaeontology, comparative anatomy, and +ontogeny. + +The thousands of other objections which have been made during the last +forty years (chiefly by outsiders) may be passed over in silence. They +do not require serious refutation. In spite of, or perhaps because of, +these attacks, the theory of Evolution stands established more firmly +than ever. + +It is easy for the outsider to exult over the difficulties which our +problem implies--difficulties which we who have given our lives to the +study understand likewise, and try our best not only to bridge over, +but also to point out. Anyhow, we do not conceal them; while those who +reject the explanation offered by Evolution make the most of the gaps, +and pass silently over the far more numerous points favourable to our +theory. + +How fruitful during the last thirty years the astonishing progress in +our palaeontological knowledge has been for our Pithecometra-thesis is +best shown by a short glance at the growth of our knowledge of fossil +Primates. Cuvier,[13] the founder of palaeontology, continued up to the +time of his death, in 1832, to assert that fossil remains of monkeys +and lemurs did not exist. The only skull of a fossil lemuroid which +he described (namely, Adapis) he declared to be that of an ungulate. +Not until 1836 were the first fragments of extinct monkeys found in +India; it was two years later, near Athens, that the skeleton of +_Mesopithecus penthelicus_ was discovered. Other remains of lemurs were +found in 1862. But during the last twenty years the number of fossil +Primates has been augmented by the remarkable discoveries of Gaudry, +Filhol, Milne Edwards, Seeley, Schlosser, and others in Europe; of +Marsh, Cope, Osborn, Leidy, Ameghino, in South America; and Forsyth +Major in Madagascar.[14] These tertiary remains, chiefly of Eocene and +Miocene date, fill many gaps between existing genera of Primates, and +afford us quite a clear insight into the phyletic development of this +order during the millions of years of the Caenozoic age. + + [13] See notes, p. 87. + + [14] + F. AMEGHINO: 'Contribucion al conocimiento de los mamiferos + de la republica Argentina.' In _Actas de la Academia nacional de + Sciencias en Cordoba_, 1889.--Another article in _Revista Argentina de + Historia natural_. Buenos Aires, 1891. + + A. GAUDRY: 'Animaux fossiles et geologie de l'Attique.' + 1862.--'Le Dryopitheque.' _Mem. Soc. geol. de France_: + 'Paleontologie.' 1890. + + O. MARSH: 'Introduction and Succession of Vertebrate Life in + America.' Address, Amer. Assoc. Adv. Sci., Nashville, 1887. + + H. F. OSBORN: 'The Rise of the Mammalia in North America.' + Address, Amer. Assoc. Adv. Sci., Madison, 1893. + + L. RUETIMEYER: 'Ueber die Herkunft unserer Thierwelt,' Basel, + 1867. + + C. S. FORSYTH MAJOR: 'Fossil Monkeys from Madagascar.' + _Geological Magazine_, 1896. + + M. SCHLOSSER: 'Ueber die Beziehungen der ausgestorbenen + Saeugethierfaunen und ihr Verhaeltniss zur Saeugethierfauna der + Gegenwart.' Biolog. Centralblatt, 1888. + +The most important difference between the two groups of existing +monkeys is indicated by their dentition. Adult man possesses, like +all the other Catarrhine Simiae, thirty-two teeth, whilst the American +monkeys (the Platyrrhinae) have thirty-six teeth--namely, one pair of +premolars more in the upper and lower jaws. Comparative odontology +leads us to the phylogenetic conclusion that this number has been +produced by reduction from a still older form with forty-four teeth. +This typical dental formula (three incisors, one canine, four +premolars, and three molars, in each half-jaw) is common to all those +most important older mammals which in the beginning of the Eocene +period constituted the four large groups of Lemuravida, Condylarthra, +Esthonychida, and Ictopsida. These are the four ancestral groups +of the four main orders of Placentalia--namely, of the Primates, +Ungulata, Rodentia, and Carnassia. They seem to be so closely related +by their primitive organization that they may be united in one common +super-order, Prochoriata. + +With a considerable degree of probability, we are led to formulate +the further hypothesis that all the orders of Placentalia--from the +lowest Prochoriata upwards to man--have descended from some unknown +common ancestor living in the Cretaceous period, and that this oldest +placental form originated from some Jurassic group of marsupials. + +Among these numerous fossil Lemures which have been discovered within +the last twenty years, there exist, indeed, all the connecting forms +of the older series of Primates, all the 'missing links' sought for by +comparative odontology. + +The oldest Lemures of the tertiary age are the Eocene Pachylemures, +or Hyopsodina. They possess the complete dentition of the +Prochoriata--namely, forty-four teeth (3.1.4.3/3.1.4.3). Then follow +the Eocene Palaeolemures, or Adapida, with forty teeth, they having lost +one pair of incisors in each jaw. To these are attached the younger +Autolemures, or Stenopida, with thirty-six teeth, they thus possessing +already the same dentition as the Platyrrhinae. The characteristic +dentition of the Catarrhinae is derived from this formula by the loss of +another premolar. + +These relations are so clear and so closely connected with a +gradual transformation of the whole skull, and with the progressive +differentiation of the Primate-form, that we are justified in saying +that the pedigree of the Primates, from the oldest Eocene Lemures +upwards to man, is now so well known, its principal features so firmly +fixed within the Tertiary age, that there is no missing link whatever. + +Quite different, and much more incomplete, is the palaeontological +evidence, if we go further back into the Secondary or Mesozoic age, +and look there for the older ancestors of the mammalian series. There +we meet everywhere with wide gaps, and the scarce fragments of fossil +Mesozoic mammals (excessively rare in the Cretaceous formation) are too +poor to permit definite conclusions as to their systematic position. +Indeed, comparative anatomy and ontogeny lead us to the hypothesis +that the oldest Cretaceous Mammalia--the Prochoriata--are descended +from Jurassic marsupials, and these again from Monotremes. We may +also suppose with high probability that among the unknown Cretaceous +Prochoriata there have been Lemuravida and forms intermediate between +these and the Jurassic Amphitheriidae, and that these marsupials in +their turn are descendants of Pantotheria or similar monotreme-like +creatures of the Triassic age. Any certain evidence for these +hypotheses is at present still wanting. One important fact, however, +is established--namely, that these interesting and oldest Mammalia--the +Pantotheria of Marsh, the Triassic Dromatheriidae, and the Jurassic +Triconodontidae of Osborn--were small insectivorous mammals with a very +primitive organization. Probably they were Monotremes, and may be +derived directly from Permian Sauromammalia, an ill-defined mixture of +Mammalia and Reptilia. + +This generalized characteristic supports our view that _the whole +class of Mammalia is monophyletic_, and that all its members, from +the oldest Monotremes upwards to man, have descended from one common +ancestor living in the older Triassic, or perhaps in the Permian, +age. To acquire full conviction of this important conception, we have +only to think of the hair and the glands of our human skin, of our +diaphragm, the heart and the blood corpuscles without a nucleus, our +skull with its squamoso-mandibular articulation. All these singular +and striking modifications of the vertebrate organization are common +to mammals, and distinguish them clearly from the other Craniota. This +characteristic combination and correlation proves that they have been +developed only _once_ in the history of the vertebrate stem, and that +they have been transferred by heredity from one common ancestor to all +the members of the class of Mammalia. + +The next step, as we trace our human phylogeny to its origin, leads us +further back into the lower Vertebrata, into that obscure Palaeozoic +age the immeasurable length of which (much greater than that of the +Mesozoic) may, according to one of the newest geological calculations, +have comprised about one thousand millions of years.[15] + + [15] See note, 'Geological Time and Evolution' p. 134. + +The first important fact we have to face here is the complete absence +of mammalian remains. Instead of these we find in the later Palaeozoic +period, the Permian, air-breathing _reptiles_ as the earliest +representatives of Amniota. They belong to the most primitive order +of that class, the Tocosauria; and besides them there were the +Theromorpha, which approach the Mammalia in a remarkable manner. These +reptiles in turn were preceded, in the Carboniferous period, by true +Amphibia, most of them belonging to the armour-clad Stegocephali. +These interesting Progonamphibia were the oldest Tetrapoda, the first +vertebrates which had adapted themselves to the terrestrial mode of +life; in them the swimming fin of fishes and Dipneusta was transformed +into the pentadactyle extremities characteristic of quadrupeds. + +To appreciate the high importance of this metamorphosis, we need only +compare the skeleton of our own human limbs with that of the living +Amphibia. We find in the latter the same characteristic composition as +in man: the same shoulder and pelvic girdle; the same single bone, the +humerus or the femur, followed by the same pair of bones in the forearm +and leg; then the same skeletal elements composing the wrist and the +ankle regions; and, lastly, the same five fingers and toes. + +The arrangement of these bones, peculiar and often complicated, but +everywhere essentially the same in all the Tetrapoda, is a striking +evidence that man is a descendant from the oldest pentadactyle Amphibia +of the Carboniferous period. In man the pentadactyle type has been +better preserved by constant heredity than in many other Mammalia, +notably the Ungulata. + +The oldest Carboniferous Amphibia, the armour-clad Stegocephali, and +especially the remarkable Branchiosauri discovered by Credner, are +now regarded by all competent zoologists as the indubitable common +ancestral group of all Tetrapoda, comprising both Amphibia and Amniota. +But whence this most remote group of Tetrapoda? That difficult question +is answered by the marvellous progress of modern palaeontology, and +the answer is in complete harmony with the older results arrived +at by comparative anatomy and ontogeny. Thirty-four years ago Carl +Gegenbaur,[16] the great living master of comparative anatomy, had +demonstrated in a series of works how the skeletal parts of the various +classes of Vertebrata, especially the skull and the limbs, still +represent a continuous scale of phyletic gradations. Apart from the +Cyclostomes, there are the fishes, and among them the Elasmobranchi +(sharks and rays), which have best preserved the original structure in +all its essential parts of organization. Closely connected with the +Elasmobranchi are the Crossopterygii, and with these the Dipneusta or +Dipnoi. Among the latter the highest importance attaches to the ancient +Australian Ceratodus. Its organization and development is now, at last, +becoming well known. This transitional group of Dipnoi, 'fishes with +lungs' but without pentadactyle limbs, is the morphological bridge +which joins the Ganoids and the oldest Amphibia. With this chain +of successive groups of Vertebrata, constructed anatomically, the +palaeontological facts agree most satisfactorily. Selachians and Ganoids +existed in the Silurian times, Dipnoi in the Devonian, Amphibia in the +Carboniferous, Reptilia in the Permian, Mammalia in the Trias. These +are historical facts of first rank. They connote in the most convincing +manner that remarkable ascending scale in the series of vertebrates +for our knowledge of which we are indebted to the works of Cuvier and +Blainville, Meckel, Johannes Mueller and Gegenbaur, Owen and Huxley. +The historical succession of the classes and orders of the Vertebrata +in the course of untold millions of years is definitely fixed by the +concordance of those leading works, and this invaluable acquisition is +much more important for the foundation of our human pedigree than would +be a complete series of all possible skeletons of Primates. + + [16] See note, p. 97. + +Greater and more frequent difficulties arise if we penetrate further +into the most remote part of the human phylogeny, and attempt to derive +the vertebrate stem from an older stem of invertebrate ancestors. None +of those had a skeleton which could be petrified; and the same remark +applies to the lowest classes of Vertebrata--to the Cyclostomes and +the Acrania. Palaeontology, therefore, can tell us nothing about them; +and we are limited to the other two great documents of phylogeny--the +results of comparative anatomy and ontogeny. The value of their +evidence is, however, so great that every competent zoologist can +perceive the most important features of the most remote portion of our +phylogeny. + +Here the first place belongs to the invaluable results which modern +comparative ontogeny has gained by the aid of the biogenetic law or +the theory of recapitulation. The foundation-stones of vertebrate +embryology had been laid by the works of Von Baer, Bischoff,[17] Remak, +and Koelliker;[18] but the clearest light was thrown upon it by the +famous discoveries of Kowalevsky[19] in 1866. He proved the identity +of the first developmental stages of Amphioxus and the Ascidians, and +thereby confirmed the divination of Goodsir, who had already announced +the close affinity of Vertebrates and Tunicates. The acknowledgment of +this affinity has proved of increasing importance, and has abolished +the erroneous hypothesis that the Vertebrata may have arisen from +Annelids or from other Articulata. Meanwhile, from 1860 to 1872, I +myself had been studying the development of the Spongiae, Medusae, +Siphonophora, and other Coelenterata. Their comparison led me to the +statements embodied in the 'Gastraeatheorie,' the first abstract of +which was published in 1872 in my monograph of the Calcispongiae. + + [17] Wilhelm Bischoff of Munich: works on the history of the + development of the rabbit, dog, guinea-pig, roe-deer. 1840-1854. + + [18] See note, p. 96. + + [19] 'Ueber die Entwicklung der einfachen Ascidien,' Mem. Acad. St. + Petersbourg, vii. ser., tome x. (1866). Other papers in 'Archiv f. + Mikroskop. Anatomie,' vii. (1871); xiii. (1877). + +These ideas were carried on and expanded during the subsequent ten +years by the help of many excellent embryologists--first of all by E. +Ray Lankester and Francis Balfour. The most fruitful result of these +widely extended researches was the conclusion that the first stages of +embryonic development are essentially the same in all the different +Metazoa, and that we may derive from these facts certain views on +the common descent of all from one ancestral form. The unicellular +egg[20] repeats the stage of our Protozoan ancestors; the Blastula +is equivalent to an ancestral coenobium of Magosphaera or Volvox; +the Gastrula is the hereditary repetition of the Gastraea, the common +ancestor of all the Metazoa. + + [20] See note, p. 115--Theory of cells. + +Man agrees in all these respects with the other vertebrates, and must +have descended with them from the same common root. + +Particularly obscure is that part of our phylogeny which extends from +the Gastraea to Amphioxus. The morphological importance of this last +small creature had been perceived by Johannes Mueller, who in 1842 +gave the first accurate description of it. It would not, of course, be +correct to proclaim the modern Amphioxus the common ancestor of all the +vertebrates; but he must be regarded as closely related to them, and +as the only survivor of the whole class of Acrania. If the Amphioxidae +had through some unfortunate accident become extinct, we should not +have been able to gain anything like a positive glimpse at our most +remote vertebrate ancestor. On the one hand, Amphioxus is closely +connected with the early larva of the Cyclostomes, which are the +oldest Craniota, and the pre-Silurian ancestors of the fishes. On the +other hand, the ontogeny of Amphioxus is in harmony with that of the +Ascidians, and if this agreement is not merely coincidental, but due to +relationship, we are justified in reconstructing for both Ascidians +and Amphioxus one common ancestral group of chordate animals, the +hypothetical _Prochordonia_. The modern Copelata give us a remote idea +of their structure. The curious Balanoglossus, the only living form of +Enteropneusta, seems to connect these Prochordonia with the Nemertina +and other Vermalia, which we unite in one large class--Frontonia. + +No doubt these pre-Cambrian Vermalia, and the common root of all +Metazoa, the Gastraeades, were connected during the Laurentian period +by a long chain of intermediate forms, and probably among these +were some older forms of Rotatoria and Turbellaria; but at present +it is not possible to fill this wide gap with hypotheses that are +satisfactory, and we have to admit that here indeed are many missing +links in the older history of the Invertebrata. Still, every zoologist +who is convinced of the truth of transformism, and is accustomed to +phylogenetic speculations, knows very well that their results are most +unequal, often incomplete. + + + + +III. + + +Let us now recapitulate the ancestral chain of man, as it is set forth +in the accompanying diagram (p. 55), which represents our present +knowledge of our descent. For simplicity's sake the many side-issues +or branches which lead to groups not in the main line of our descent +have been left out, or have been indicated merely. Many of the stages +are of course hypothetical, arrived at by the study of comparative +anatomy and ontogeny; but an example for each of them has been taken +from those living or fossil creatures which seem to be their nearest +representatives. + +1. The most remote ancestors of all living organisms were living beings +of the simplest imaginable kind, organisms without organs, like +the still existing _Monera_. Each consisted of a simple granule of +protoplasm, a structureless mass of albuminous matter or plasson, like +the recent Chromaceae and Bacteriae. The morphological value of these +beings is not yet that of a cell, but that of a cytode, or cell without +a nucleus. Cytoplasm and nucleus were still undifferentiated. + +I assume that the first Monera owe their existence to spontaneous +creation out of so-called anorganic combinations, consisting of carbon, +hydrogen, oxygen, and nitrogen. An explanation of this hypothesis I +have given in my 'Generelle Morphologie.' + +The Monera probably arose early in the Laurentian period. The oldest +are the Phytomonera, with vegetable metabolism. They possessed the +power (characteristic of plants) of forming albumin by synthesis from +carbon, water, and ammonia. From some of these plasma-forming Monera +arose the plasmophagous Zoomonera with animal metabolism, living +directly upon the produce of their plasmodomous or plasma-forming +sisters. This is the first instance of the great principle of division +of labour. + +2. The second stage is that of the _simple and single cell_, a bit +of protoplasm with a nucleus. Such unicellular organisms are still +very common. The _Amoebae_ are their simplest representatives. The +morphological value of such beings is the same as that of the egg +of any animal. The naked egg cells of the sponges creep about in an +amoeboid fashion, scarcely distinguishable from Amoeba. The same +remark applies to the egg-cell of man himself in its early stages +before it is enclosed in a membrane. The first unicellular organisms +arose from Monera through differentiation of the inner nucleus from the +outer protoplasm. + +3. Repeated division of the unicellular organism produces the +_Synamoebium_, or community of Amoebae, provided the divisional +products, or new generations of the original cell, do not scatter, +but remain together. The existence of such a _Coenobium_, a number +of equal and only loosely-connected cells, as a separate stage in the +ancestral history of animals, is made highly probable by the fact that +the eggs of all animals undergo after fertilization such a process of +repeated self-division, or 'cleavage,' until the single egg cell is +transformed into a heap of cells closely packed together, not unlike a +mulberry (_morula_)--hence _morula_ stage in ontogeny. + +4. The morula of most animals further changes into a _Blastula_, a +hollow ball filled with fluid, the wall being formed by a single layer +of cells, the blastoderm or germinal layer. This modification is +brought about by the action of the cells--they conveying nourishing +fluid into the interior of the whole cell colony and thereby +being themselves forced towards the surface. The Blastula of most +Invertebrata, and even that of Amphioxus, is possessed of fine ciliae, +or hair-like processes, the vibrating motion of which causes the whole +organism to rotate and advance in the water. Living representatives of +such Blastaeads, namely, globular gelatinous colonies of cells enclosing +a cavity, are Volvox and Magosphaera. + +5. The Blastula of most animals assumes a new larval form called +_Gastrula_, in which the essential characteristics are that a portion +of the blastoderm by invagination converts the Blastula into a cup +with double walls, enclosing a new cavity, the primitive gut. This +invagination or bulging-in obliterates the original inner cavity of +the Blastula. The outer layer of the Gastrula is the ectoderm, the +inner the endoderm; both pass into each other at the blastoporus, or +opening of the gut cavity. The Gastrula is a stage in the embryonic +development of the various great groups of animals, and some such +primitive form as ancestral to all Metazoa is thus indicated. This +hypothetical _Gastraea_ is still very essentially represented by the +lower Coelenterates--_e.g._, Olynthus, Hydra. + +6. The sixth stage--that of the _Platodes_, or flat-worms--is very +hypothetical. They are bilateral gastraeads, with a flattened oblong +body, furnished with ciliae, with a primitive nervous system, simple +sensory and reproductive organs, but still without appendages, body +cavity, vent, and blood-vessels. The nearest living representatives of +such creatures are the acoelous Turbellarians--_e.g._, Convoluta, a +free-swimming, ciliated creature. + +7. The next higher stage is represented by such low animals as the +_Gastrotricha_--_e.g._, Chaetonotus among the Rotatoria, which differ +from the rhabdocoelous Turbellarians chiefly by the formation of +a vent and the beginnings of a coelom, or cavity, between gut and +body wall. The addition of a primitive vascular system and a pair of +nephridia, or excretory organs, is first met with in the _Nemertines_. + +8. These, together with the _Enteropneusta_ (Balanoglossus), are +comprised under the name of Frontonia, or Rhynchelminthes, and form the +highest group of the Vermalia. + +The Enteropneusta especially fix our attention, because they alone, +although essentially 'worms,' exhibit certain characteristics which +make it possible to bridge over the gulf which still separates the +Invertebrata from the vertebrate phylum. The anterior portion of the +gut is transformed into a breathing apparatus--hence Gegenbaur's +term of Enteropneusta, or Gut-breathers. Moreover, Balanoglossus and +Cephalodiscus possess another modification of the gut--namely, a +peculiar diverticulum, which, in the present state of our knowledge, +may be looked upon as the forerunner of the chorda dorsalis. + +9. Stage of _Prochordonia_, as indicated by the larval form, called +Chordula, which is common to the Tunicata and all the Vertebrata. +These two groups possess three most important features: (_a_) A chorda +dorsalis, a stiff rod lying in the long axis of the body, dorsally from +the gut and below the central nervous system. This latter, for the +first time in the animal kingdom, appears in the shape of a spinal +cord. (_b_) The use of the anterior portion of the gut for respiratory +purposes. (_c_) The larval development of the Tunicata is essentially +the same as that of the Vertebrata in its early stages. Only the +free-swimming Copelata or Appendicularia among the Tunicates retain +most of these features. The others, which become sessile--namely, the +Ascidiae, or sea-squirts--degenerate and specialize away from the main +line. + +10. Stage of the _Acrania_, represented by Amphioxus. The early +development of this little marine creature agrees closely with +that of the Tunicates; but one important feature is added to its +organization--namely, metamerism, segmentally arranged mesoderm. +Amphioxus still possesses neither skull nor vertebrae, neither ribs +nor jaws, and no limbs. But it is a member of the Vertebrata if we +define these as follows: Bilateral symmetrical animals with segmentally +arranged mesoderm, with a chorda dorsalis between the tubular nervous +system and the gut, and with respiratory organs which arise from the +anterior portion of the gut. We do not assume that Amphioxus stands +in the direct ancestral line; it is probably much specialized, partly +degenerated, and represents a side-branch; but it is, nevertheless, +the only creature, hitherto known, which satisfactorily connects the +Vertebrata with their invertebrate ancestors. Many other efforts have +been made to solve the mystery of the origin of the Vertebrata--all +less satisfactory than the present suggestion, or even absolutely +futile. This remark applies especially to the attempts to derive them +from either Articulata or Echinoderms. The other great and highly +developed phylum, the Mollusca, is quite out of the question. We have +to go back to a level at which all these principal phyla meet, and +there we find the Vermalia, the lower of which alone permit connection +in an upward direction with the higher phyla. + + ANCESTRAL TREE OF THE VERTEBRATA. + + _Abridged from 'Systemat. Phylogenie,' Sec. 15._ + + Names underlined refer to hypothetical groups. + + _Mammalia_ + _Aves_ | + | _Reptilia_ | + | | | + +----------------+ | + | | + +--------------+ + | + _Proreptilia_ + | _Amphibia_ + _Pisces_ | | + | | +----------+ + | | | + | | | _Dipnoi_ + | _Stegocephali_ | + | | | + | +---------------+ + | | + +---------------+ + | _Cyclostomata_ + _Proselachii_ | + | | + _Tunicata_ | +--------+ + | | | + | *_Archicrania_* + | | _Acrania_ + | | | + | *_Prospondylia_*------+ + | | + +----------+ | + | | + *_Prochordonia_* + + +11. Stage of _Cyclostomata_. This now small group of Lampreys and +Hagfishes represents the lowest Craniota; and although much specialized +as a side-branch of the main-stem from which the other Craniota have +sprung, they give us an idea of what the direct ancestors of the latter +must have been like:--still without visceral arches, without jaws and +without paired limbs; with a persistent pronephros; the ear with one +semicircular canal only; mouth suctorial; cranium very primitive; +and the metamerism of the vertebral column indicated only by little +blocks of cartilage in the perichordal sheath. Such creatures must +have existed at least as early as the Lower Silurian epoch; but until +1890 fossil Cyclostomes were unknown. Their life in the mud, or as +endoparasites of fishes, coupled with their soft structure, makes them +very unfit for preservation. This gives all the greater importance to +Traquair's discovery, in 1890, of many little creatures, called by him +_Palaeospondylus gunni_, in the Old Red Sandstone of Caithness, which +seem to be very closely allied to Cyclostomata. + +12. The _Elasmobranchi_ (sharks and skates), with their immediate +forerunners, the Acanthodi of the Devonian and Carboniferous age, +are the first typical fishes. That they existed as far back as the +Silurian age is proved by many enamelled spines of the dermal armour, +chiefly from the dorsal fins. This higher stage is characterized by the +possession of typical jaws, by visceral or gill-bearing arches, and by +two pairs of limbs. None of the Elasmobranchs, fossil or recent, stands +in the direct ancestral line; but they are the lowest Gnathostomata, +jaw-and-limb-possessing creatures, known. + +13. Closely connected with the Elasmobranchs in a wider sense are the +_Crossopterygii_, which begin in the Devonian age as a large group, but +have left only two survivals, the African Polypterus and Calamoichthys. +They are possessed of dermal bones and other ossifications, and are +characterized by their lobate paired fins, which have a thick axis +beset with biserial fin rays. Their gill-clefts are covered by an +operculum, and they have a well-developed air-bladder. Whilst they +are in many respects more highly developed than the Elasmobranchs, +and are intimately connected with the typical Ganoids and other +bony fishes (all of which form a great, manifold side-branch of the +general vertebrate stem), they stand in many other respects (notably, +the structure of the paired fins, the vertebral column, and the +air-bladder) nearer the main-stem of our own ancestral line. + +14. This is shown by their intimate relation to the _Dipnoi_, which +are still represented by the Australian, African, and South American +mud-fishes: Ceratodus, Protopterus, and Lepidosiren. The genus +Ceratodus existed in the Upper Trias, whence various other unmistakably +dipnoous forms lead down through the Carboniferous (_e.g._, Ctenodus) +to the Devonian strata--_e.g._, Dipterus. They are characterized as +follows: The paired fins still retain the archipterygial form (namely, +one axis with biserial rays); the heart is already trilocular, and +receives blood which is mixed arterial and venous, owing to the gills +being retained, while the air-bladder has been modified into a lung. In +fact, the generalized Dipnoi form the actual link between fishes and +_Amphibia_. + +15. _Amphibia._ The earliest amphibian fossils occur in +the Carboniferous strata. They alone--the Stegocephali or +Phractamphibia--stand in the ancestral line, while the Lissamphibia, to +which all the recent forms belong, are side-branches. The Stegocephali +are the earliest Tetrapoda, the archipterygial paired fins having been +transformed into the pentadactyle fore and hind limbs, which are so +characteristic of all the higher Vertebrata. The cranium is roofed +over by dermal bones, of which, besides others, supra-occipitals, +supra-orbitals, and supra-temporals are always present. The lowest +members (Branchiosauri) still retained gills besides the lungs, while +others (Microsauri) have lost the gills. Be it remembered that all +the recent Amphibia still undergo the same metamorphosis during their +ontogenetic development. + +In the very important Temnospondyli, a subgroup of the +Stegocephali--_e.g._, Trimerorhachis of the Lower Red Sandstone or +Lower Permian--the component cartilaginous or bony units which compose +the vertebrae still remained in a separate, unfused state, showing at +the same time an arrangement whence has arisen that which is typical +of the Amniota. The same applies to the limbs and their girdles. In +fact, the Stegocephali, taken as a whole, lead imperceptibly to the +_Proreptilia_. + +16. _Proreptilia_ are represented by the Permian genera Eryops and +Cricotus. Until quite recently these and many other fossils from +the Carboniferous strata were looked upon as Amphibia, while many +undoubted fossil Amphibia were mistaken for reptiles, as indicated by +the frequent termination '-saurus' in their names. + +The nearest living representative of these extinct Proreptilia is +the New Zealand reptile Hatteria, or Sphenodon, close relations +of which are known from the Upper Trias; while others--_e.g._, +Palaeohatteria--have been discovered in the Permian. Anyhow, Sphenodon +is the reptile which stands nearest to the main stem of our ancestry. + +The most important characteristics of the Reptilia, which mark a higher +stage or level, are (1) The entire suppression of the gills--although +during the embryonic development the gill-clefts still appear in all +reptiles, birds, and mammals; (2) The development of an amnion and an +allantois, both for the embryonic life only, but so characteristic +that all these animals are comprised under the name of Amniota; +(3) The articulation of the skull with the first neck vertebrae by +well-developed condyles, either single (really triple) or double (such +a condylar arrangement begins with the Amphibia, but only the two +lateral condyles are developed, while the middle portion, belonging to +the basi-occipital element, remains rudimentary[21]); (4) The formation +of centra, or bodies of the vertebrae, mainly by a ventral pair of the +original quadruple constituents, or arcualia. + + [21] Similar conditions seem to have prevailed among the Proreptilia; + but in those of their descendants which have specialized into Reptiles + and Birds the basi-occipital element becomes more and more predominant + in that formation which ultimately leads to the apparently single + condyle. Hence it is misleading to divide the Tetrapoda into the two + main groups of Amphi-and Mono-condylia, and therefrom to conclude that + the two-condyled Mammalia are more closely related to the likewise + amphicondylous Amphibia than to the so-called monocondylous Reptiles. + +17. Between the Proreptilia and the Mammalia, which latter occur in +the Upper Triassic epoch, we have necessarily to intercalate a group +of very low reptiles, which are still so generalized that their +descendants could branch off either into the Reptilia proper or into +the Mammalia. The changes concerned chiefly the brain and the heart; +of the skeleton, the skull and the pelvis; and, of the tegumentary +structures, the formation of a hairy covering. Many such creatures +existed in the Triassic epoch--namely, the _Theromorpha_--some of which +indeed possess so many characteristics which otherwise occur in the +Mammalia only, that these creatures have been termed _Sauro-Mammalia_. +However, it has to be emphasized that none of the Theromorpha hitherto +discovered fulfils all the requirements which would entitle them to +this important linking position. They only give us an approximate idea +of what this link was like. + +18. Stage of the _Promammalia_, or _Prototheria_. The only surviving +members are the famous duck-bill, Ornithorhynchus, and the spiny +ant-eaters, Echidna and Proechidna, of the Australian region. These +few genera, however, differ so much from one another in various +important respects that they cannot but be remnants of an originally +much larger group. Indeed, many fossils from the Upper Triassic and +from the Jurassic strata have without much doubt to be referred to the +Prototheria. The Prototheria are typical mammals, because they possess +the following characteristics: The heart is completely quadrilocular; +the blood is warm, and its red corpuscles have, owing to the loss +of their nucleus, been modified from biconvex into biconcave discs; +they have a hairy coat and sweat glands, and two occipital condyles; +the ilio-sacral connection is preacetabular; the ankle-joint is +cruro-tarsal; the quadrate bone of the Reptilia has ceased to carry the +under jaw, which now articulates directly with the squamosal portion +of the skull. Their low position is shown by the retention of the +following reptilian features: Complete coracoid bones and a T-shaped +interclavicle; a cloaca, or common chamber for the passage of the +faeces, the genital and the urinary products; they are still oviparous; +the embryo develops without a chorion, and is therefore not nourished +through a placenta. Even the milk glands, which are absolutely +peculiar to the Mammalia, are still in a very primitive stage, and do +not yet produce milk proper; and there is only a temporary shallow +marsupium. + +19. Stage of _Metatheria_, or _Marsupialia_, are direct descendants of +Prototheria; but they show higher development by the reduction of the +coracoid bones and the interclavicle. The original cloaca is divided +into a rectal chamber and a uro-genital sinus, completely separated, +at least in the males; they are viviparous; the young are received +into a permanent marsupium, in the walls of which are formed typical +milk glands and nipples, but the embryo is still devoid of a placenta, +although some recent marsupials show indications of such an organ. The +corpus callosum in the brain is still very weak. + +Most of the marsupials are extinct. They occur from the Upper Trias +onwards, and had in the Jurassic epoch attained a wide distribution +both in Europe and in America. Since the Tertiary epoch they have +been restricted to America and to the Australian region, and are now +represented by about 150 species. + +20. Stage of _Prochoriata_, or early _Placentalia_: a further +development of the Metatheria by the development of a placenta, loss +of the marsupium and the marsupial bones, complete division by the +perineum of the anal and uro-genital chambers, stronger development of +the corpus callosum, or chief commissure of the two hemispheres of the +brain. + +Placentalia must have come into existence during the Cretaceous +epoch. Up to that time all the Mammalia seem to have belonged to +either Prototheria or to Metatheria; but in the early Eocene we can +distinguish the main groups of Placentalia--namely, (1) Trogontia, now +represented by the rodents; (2) Edentata, or sloths, armadilloes, etc.; +(3) Carnassia, or Insectivora and Carnivora; (4) Chiroptera, or bats; +(5) Cetomorpha, or whales and dugongs; (6) Ungulata; (7) Primates. +Of these groups, the first and second, third and fourth, fifth and +sixth, can perhaps, to judge from palaeontological evidence, be combined +into three greater groups, as indicated by the fossil Esthonychida, +Ictopsida, and Condylarthra, in addition to the ancestral Primates, +or Lemuravida, as the fourth large branch of the ancestral-tree where +this has reached the placental level. Among none of the first three +branches can we look for the ancestors of the Primates. The Lemuravida, +therefore, represent a branch equivalent to the three other branches. + +21. Stage of _Lemures_, or _Prosimiae_, comprising the older members of +the Primates, consequently approaching most nearly to the Lemuravida. +The limbs are modified into pentadactyle hands and feet of the arboreal +type, and are protected by nails. The dentition is of the frugivorous +or omnivorous type, with an originally complete series of teeth, with +milk teeth and with permanent. The orbit is surrounded by a complete +bony ring, posteriorly by a fronto-jugal arch, but still widely +communicating with the temporal fossa. The placenta is diffuse and +non-deciduous. + + ANCESTRAL TREE OF THE MAMMALIA. + + _'Systematische Phylogenie,' Sec. 386._ + + _Perissodactyla_ _Homo_ _Carnivora_ + | (_Litopterna_) | | _Pinnipedia_ + | | | | | + +-------+ _Anthropoidae_ +------+ + _Artiodactyla_ | | | + | | | _Carnassia_ + +----------+ _Catarhinae_ | + | | _Chiroptera_ | + _Proboscidea_ | | | _Insectivora_ | + | | _Platyrhinae_ | | | + (_Amblypoda_) | | | | +-------+ + | | | | | | _Rodentia_ + +-------+ | _Simiae_ +-------+ | + | | | | (_Tillodontia_) + +--+ | | | + _Cetacea_ | | | _Trogontia_ + | _Sirenia_ | _Lemures_ _*Ictopsales*_ | _Edentata_ + | | | | | | | + _Cetomorpha_ | _Hyracoidea_ | | _*Esthonychales*_ + | | | | | | + +---_?_---+------+ | | | + | _*Lemuravidae*_ | | + _*Condylarthrales*_ | +-------+ | + | | | | + +--------Eutheria s. Placentalia------------------+ + | + | _Marsupialia polyprotodontia_ + _Marsupialia diprotodontia_ | | + | | | + +-------------Metatheria--------------+ + | + | _Monotremata_ + | | (_Allotheria_) + | | | + | +-----------------+ + | | + Prototheria-----+ + | + | + _*Hypotheria s.*_ _*Promammalia*_ + + _Names in brackets indicate extinct groups. + Names *underlined* indicate hypothetical groups or combinations._ + +22. Stage of _Simiae_. Orbit completely separated from the temporal +fossa by an inward extension of the frontal and malar bones meeting the +alisphenoid. Placenta consolidated into a disc, and with a maternal +deciduous portion. Mammae pectoral only. The dental formula is 2.1.3.3. +All the fingers and toes are protected by flat nails. The tail is long. +The American prehensile-tailed monkeys are a lower side-branch. + +23. Stage of _Catarrhinae Cercopithecidae_. The dental formula is +2.1.2.3, owing to the loss of one pair of premolars in each jaw. +The frontal and alisphenoid bones are in contact, separating the +parietal from the malar bone; this feature is correlated with the +enlarged brain. The internarial septum is narrow, and the nostrils +look forwards and downwards instead of sidewards--hence the term +'Catarrhinae.' The external auditory meatus is long and bony. The tail +is long, with the exception of _Macacus inuus_. The body is covered +with a thick coat of furry hair. Catarrhine monkeys have existed, we +know with certainty, since the Miocene. + +24. Stage of _Catarrhinae Anthropoidae_, or _Apes_. Now represented by +the large apes--namely, the Hylobates or gibbon of South-Eastern Asia, +_Simia satyrus_, the orang-utan of Sumatra and Borneo, _Troglodytes +gorilla_, _T. niger_ and _T. calvus_, the gorilla and the chimpanzees +from Western Equatorial Africa. Of fossils are to be mentioned +Pliopithecus and Dryopithecus from European Miocene, and _Troglodytes +sivalensis_ from the Pliocene of the Punjaub. The tail is reduced +to a few caudal vertebrae, which are transformed into a coccyx, not +visible externally; but in the embryos of apes and man the tail is +still a conspicuous feature. The walk is semierect; in adaptation +to the prevailing arboreal life, the arms are longer than the legs. +The hair of the body is considerably more scanty than in the tailed +monkeys. _Troglodytes calvus_, a species or variety of chimpanzee, is +bald-headed. None of the recent genera of apes can lay claim to a place +in the ancestry of mankind. + +25. Stage of _Pithecanthropi_. Hitherto the only known representative +is _Pithecanthropus erectus_, from the Upper Pliocene of Java. In +adaptation to a more erect gait, the legs have become stronger and the +hind-hand has been turned into a flat-soled walking 'foot.' The brain +is considerably enlarged. Presumably it is still devoid of so-called +articulate speech; this is indicated by the fact that children have +to learn the language of their parents, and by the circumstance that +comparative philology declares it impossible to reduce the chief human +languages to anything like one common origin. + +26. _Man._ Known with certainty to have existed as an implement-using +creature in the last Glacial epoch. His probable origin cannot, +therefore, have been later than the beginning of the Plistocene. The +place of origin was probably somewhere in Southern Asia. + +Whilst we have to admit that there are great defects in the older +(invertebrate) portion of our pedigree, we have all the more reason to +be satisfied with the positive results of our investigation of the more +recent (vertebrate) part of it. All modern researches have confirmed +the views of Lamarck, Darwin, and Huxley, and they allow of no doubt +that the nearest vertebrate ancestors of mankind were a series of +Tertiary Primates. + +Particularly valuable are the admirable attempts of the two zoologists, +Paul and Fritz Sarasin,[22] to throw light upon the human phylogeny by +painstaking comparison of all the skeletal parts of man with those of +the anthropoid apes. They have shown that among the lower races of man +the primitive Veddahs of Ceylon approach the apes most nearly, and that +among the latter the chimpanzee stands nearest to man. + + [22] 'Ergebnisse naturwissenschaftlicher Forschungen auf Ceylon,' vols. + 4 and 5. (With an atlas of 84 plates; 1893.) + +The direct descent of man from some extinct ape-like form is now beyond +doubt, and admits of being traced much more clearly than the origin +of many another mammalian order. The pedigrees of the Elephants, the +Sirenia, the Cetacea, and, above all, of the Edentata, for example, +are much more obscure and difficult to explain. In many parts of their +organization--for example, in the number and structure of his five +digits and toes--man and monkeys have remained much more primitive than +most of the Ungulata. + +The immense significance of this positive knowledge of the origin of +man from some Primate does not require to be enforced. Its bearing +upon the highest questions of philosophy cannot be exaggerated. Among +modern philosophers no one has perceived this more deeply than Herbert +Spencer.[23] He is one of those older thinkers who before Darwin were +convinced that the theory of development is the only way to solve +the 'enigma of the world.' Spencer is also the champion of those +evolutionists who lay the greatest weight upon _progressive heredity_, +or the much combated _heredity of acquired characters_. From the first +he has severely attacked and criticised the theories of Weismann, who +denies this most important factor of phylogeny, and would explain +the whole of transformism by the 'all-sufficiency of selection.' In +England the theories of Weismann were received with enthusiastic +acclamation, much more so than on the Continent, and they were called +'Neo-Darwinism,' in opposition to the older conception of Evolution, +or 'Neo-Lamarckism.' Neither of those expressions is correct. Darwin +himself was convinced of the fundamental importance of progressive +heredity quite as much as his great predecessor Lamarck; as were also +Huxley and Spencer. + + [23] 'Principles of Biology': 'The Factors of Organic Evolution'; 'The + Inadequacy of Natural Selection.' + +Three times I had the good fortune to visit Darwin at Down, and on each +occasion we discussed this fundamental question in complete harmony. +I agree with Spencer in the conviction that progressive heredity is +an indispensable factor in every true monistic theory of Evolution, +and that it is one of its most important elements. If one denies with +Weismann the heredity of acquired characters, then it becomes necessary +to have recourse to purely mystical qualities of germ-plasm. I am of +the opinion of Spencer, that in that case it would be better to accept +a mysterious creation of all the various species as described in the +Mosaic account. + +If we look at the results of modern anthropogeny from the highest point +of view, and compare all its empirical arguments, we are justified in +affirming that _the descent of man from an extinct Tertiary series of +Primates is not a vague hypothesis, but an historical fact_. + +Of course, this fact cannot be proved _exactly_. We cannot explain all +the innumerable physical and chemical processes, all the physiological +mutations, which have led during untold millions of years from the +simplest Monera and from the unicellular Protista upwards to the +chimpanzee and to man. But the same consideration applies to all +historical facts. We all believe that Aristotle, Caesar, and King Alfred +did live; but it is impossible to give a proof within the meaning of +modern exact science. We believe firmly in the former existence of +these and other great heroes of thought, because we know well the works +they have left behind them, and we see their effects in the history +of human culture. These indirect arguments do not furnish stronger +evidence than those of our history as vertebrates. We know of many +Jurassic mammals only a single bone, the under jaw. We all believe that +these mammals possessed also an upper jaw, a skull, and other bones. +But the so-called 'exact school,' which regards the transformation of +species as a hypothesis not proven, must suppose that the mandibula was +the only bone in the body of these curious animals. + +Looking forward to the twentieth century, I am convinced that it will +universally accept our theory of descent, and that future science +will regard it as the greatest advance made in our time. I have no +doubt that the influence of the study of anthropogeny upon all other +branches of science will be fruitful and auspicious. The work done in +the present century by Lamarck and Darwin will in all future times be +considered one of the greatest conquests made by thinking man. + + EVOLUTIONARY STAGES OF THE PRINCIPAL GROUPS OF VERTEBRATA.[24] + + STAGES OF THE CLASSES. STAGES OF THE HEART. + PAIRED LIMBS. + + { 1. _Acrania._ I. _Leptocardia._ + I. _Adactylia_ { Cold-blooded; heart + s. _Impinnata_. { with one chamber; + Without jaws { without lungs. + and limbs. { + { 2. _Cyclostomata._ } II. _Ichthyocardia._ + } Cold-blooded; heart + } two-chambered, with + } one atrium and one + } ventricle; heart + } containing venous + } blood only; without + II. _Polydactylia_ { 3. _Pisces._ } lungs. + s. _Pinnata_. { + With two { } III. _Amphicardia._ + pairs of fins. { 4. _Dipnoi._ } Cold-blooded; heart + } with three complete + } chambers, namely, with + } two atria and one + } ventricle, or (Reptilia) + { 5. _Amphibia._ } two ventricles with still + { } incomplete septum; heart + { } containing mixed venous + { } and arterialized + III. _Pentadactylia_ { 6. _Reptilia._ } blood; with lungs. + s. _Tetrapoda_. { + With two pairs { { IV. _Thermocardia._ + of pentadactyle { { Warm-blooded; heart + limbs (unless { 7. _Aves._ { with four complete + they have { { chambers, namely, two + been lost by { { auricles and two + reduction). { { ventricles; right half + { { of the heart with venous, + { { left half with + { { arterialized, blood; with + { 8. _Mammalia._ { lungs. + + + [24] Abridged from Haeckel's 'Systematische Phylogenie der + Vertebraten,' Sec. 14. + + + + + BIOGRAPHICAL SKETCHES + + +JEAN BAPTISTE DE MONET, CHEVALIER DE LAMARCK, was born on +August 1, 1744, in Picardy, where his father owned land. Originally +educated for the Church, he soon enlisted, and distinguished himself +in active service. Owing to an accident affecting his health, the +young Lieutenant gave up the military career, and, without means, +studied medicine and natural sciences at Paris. In 1778 appeared his +'Flore francaise.' In 1793 he was appointed to a Chair of Zoology at +the newly-formed Musee d'Histoire Naturelle. He had the misfortune to +become gradually blind, and the last years of his life were spent amid +straitened circumstances. He died in 1829. + +In 1794 Lamarck divided the whole animal kingdom into vertebrate and +invertebrate animals, and founded successively the groups of Crustacea, +Arachnida, Annelida, and Radiata. Between 1816 and 1822 he published +his celebrated 'Histoire naturelle des Animaux sans Vertebres.' + +His most famous work is the 'Philosophie zoologique,' 1809. + +Assuming the spontaneous origin of life, he propounded the doctrine +that all animals and plants have arisen from low forms through +incessant modifications and changes. In this respect he was in absolute +opposition to Cuvier, who upheld the immutability of species, and did +his best by absolute silence to suppress the spread of the new doctrine. + +Lamarck has explained his views of transformism chiefly in the seventh +chapter of the first volume of his 'Philosophie zoologique.' + +Organisms strive to accommodate or adapt themselves to new +circumstances, or to satisfy new requirements--_e.g._, climate, mode +of procuring food, escape from enemies. The continued function of +parts of an organism changes the old and produces new organs. The +acquirements are inherited by the offspring, and thus are produced the +more complicated from simpler organisms. Continued disuse brings about +degeneration and ultimate loss of an organ. + +Lamarck consequently sees in the adaptability, or power of adaptation, +which he assumes for all living matter the ultimate cause of variation; +and, as he was certainly the first to point out that acquired +characters are inherited by the progeny, he has given a working +explanation of Evolution. + +But his doctrine did not spread--partly because he was misunderstood. +His theory, that a new want, by making itself felt, exacts from the +animal new exertions, perhaps from parts hitherto not used, until the +want is satisfied--this way of putting it sounds too teleological +to explain the yearned-for change in a mechanical or natural way. +Moreover, many of his examples lacked the exact basis of experiment +and observation necessary for their acceptance. Witness that of the +neck of the giraffe,--a never-failing source of ridicule to men who +cannot see the deeper purpose underlying the well-meant attempt at +an explanation, which failed from want of complete knowledge of the +intricate circumstances. + +However, the theory of transformism was, so to speak, in the air; +and various authors have written on the subject, filling the gap +between Lamarck and Darwin, especially Goethe, Treviranus, Leopold +von Buch, and Herbert Spencer. But it is Darwin's immortal merit to +have opened our eyes by his theory of natural selection, which is, at +least, the first attempt to explain some of the causes and incidents +of organic Evolution in a natural mechanical way. Moreover, he was +the first clearly to express the fundamental principles of the theory +of descent, to elaborate what had been at best a general sketch of an +ill-defined problem, and to enter into detail, supported by a host +of painstaking observations, the making of which had taken him half a +lifetime. Darwin, without going further than cursorily into the causes +of variation, argued as follows: We know that variations do occur +in every kind of living creatures. Some of these variations lead to +something, while others do not. An enormously greater number of animals +and plants are born than reach maturity and can in their turn continue +the race. What is the regulating factor? His answer is, The struggle +for existence--in other words, the weeding out of the less fit, or +rather of the owners of those variations which are not so well adapted +to their surroundings. + +For 'adapted' we had better read 'adaptable,' because a variation which +does not answer, which cannot be made use of, or, still more notably, +is a hindrance or disadvantage, does not become an adapted feature. +There is often a confusion between adaptation as an accomplished +fact, a feature, or resultant condition, and adaptation as the mode +of fitting the organism to, or making the best of, the prevailing +surroundings or circumstances. + +ETIENNE GEOFFROY SAINT-HILAIRE was born in 1772 at Etampes, +Seine-et-Oise. He was originally brought up for the Church; but when +already ordained he attended lectures on natural science and medicine +in Paris. He managed to get the place of assistant in the Musee +d'Histoire Naturelle; he became Professor of Zoology in 1793, and took +the opportunity of encouraging young Cuvier. Later he became Professor +of Zoology of the Faculte des Sciences, and in 1818 he published his +remarkable 'Philosophie anatomique.' He died in 1844. + +He had conceived the 'unity of organic composition,' meaning that there +is only one plan of construction,--the same principle, but varied in +its accessory parts. In 1830, when Geoffroy proceeded to apply to the +Invertebrata his views as to the uniformity of animal composition, +he found a vigorous opponent in Cuvier. Geoffroy, like Goethe, held +that there is in Nature a law of compensation, or balancing of growth, +so that if one organ take on an excess of development, it is at the +expense of another part; and he maintained that, since Nature takes no +sudden leaps, even organs which are superfluous in any given species, +if they have played an important part in other species of the same +family, are retained as rudiments, which testify to the permanence +of the general plan of creation. It was his conviction that, owing +to the conditions of life, the same forms had _not_ been perpetuated +since the origin of all things, although it was not his belief that +existing species were becoming modified. Cuvier, on the other hand, +maintained the absolute invariability of species, which, he declared, +had been created with regard to the circumstances in which they were +placed, each organ contrived with a view to the function it had +to fulfil,--thus putting the effect for the cause ('Encyclopaedia +Britannica,' 9th edition, vol. xxi., p. 171). + +GEORGE CUVIER was born in 1769 at Montbeliard, in the department of +Doubs, which at that time belonged to Wuerttemberg. He was educated at +Stuttgart, and studied political economy. While acting as private tutor +to a French family in France he followed his favourite pursuit, the +study of natural sciences. Geoffroy Saint-Hilaire heard of him, and +appointed him assistant in the department of comparative anatomy in the +Musee d'Histoire Naturelle. In 1799 he was elected Professor of Natural +History at the College de France, and soon after he became Perpetual +Secretary of the Institut National. In 1831, a year before his death, +Louis Philippe raised him to the rank of a peer of France. + +Cuvier was the first to indicate the true principle upon which the +natural classification of animals should be based--namely, their +structure. It is the study of the anatomy of the creatures and their +comparison which affords the only sound basis of a classification. +The work which had the greatest influence upon the scientific public +is his 'Regne animal distribue d'apres son Organisation,' 1817. The +system which he propounded in this book gradually came to have almost +world-wide fame, and, in spite of its many obvious deficiencies, still +lingers in some of our most recent text-books. + +A standard work is his 'Lecons d'Anatomie comparee,' and, in truth, he +is the founder of that kind of comparative anatomy which was brought +to such a high state by his pupil, the late Sir Richard Owen. Cuvier +discovered the law of 'correlation of growth,' and was the first to +apply this law to the reconstruction of animals from fragments: see his +monumental work entitled 'Recherches sur les Ossemens fossiles,' 1812. + +Cuvier, however, as a strict matter-of-fact man, was incapable of +appreciating the speculative conclusions which were drawn by his +contemporaries Saint-Hilaire and Lamarck. On the contrary, he firmly +stuck to the doctrine of the immutability of species; and, in order to +account for the existence of animals whose kind exists no longer, he +invented the famous doctrine of successive cataclysms. + +KARL ERNST VON BAER was born in 1792 in Esthonia, studied at Dorpat +and then at Wuerzburg, where Doellinger introduced him to comparative +anatomy. For a few years he was a _Privat-docent_ at Berlin; then he +went to Koenigsberg as Professor of Zoology and Embryology. In 1834 +he became an Academician at St. Petersburg, where for many years he +was occupied with the most varied studies, chiefly geographical and +ethnological. The last years of his long, active life he spent in +contemplative retirement on his paternal estate, and he died at Dorpat +in 1876. + +While still at Wuerzburg he induced his friend Pander, a young man +of means, to study the development of the chick; and Pander was the +first to start the theory of the germinal layers from which all the +organs arise. Baer, however, continued these researches in Koenigsberg, +and after nine years' labour produced his epoch-making work, 'Ueber +Entwicklungsgeschichte der Thiere: Beobachtung und Reflexion,' +Koenigsberg, 1828. Nine years later he completed the second volume. +He established upon a firm basis the theory of the germinal layers, +and by further 'reflexions' arrived at the elucidation of some of the +most fundamental laws of biology. For example, in the first volume +he made the following prophetic statement: 'Perhaps all animals are +alike, and nothing but hollow globes at their earliest developmental +beginning. The farther back we trace their development, the more +resemblance we find in the most different creatures. And this leads to +the question whether at the beginning of their development all animals +are essentially alike, and referable to one common ancestral form. +Considering that the "germ" (which at a certain stage appears in the +shape of a hollow globe or bag) is the undeveloped animal itself, we +are not without reason for assuming that the common fundamental form is +that of a simple vesicle, from which every animal is evolved, not only +theoretically, but historically.' + +This statement is all the more wonderful when we consider that the +cells, the all-composing individual units, were not discovered until +ten years later. + +In 1829 Baer discovered the human egg, and later the chorda dorsalis. +In an address delivered in 1834, entitled 'The Most Universal Law +of Nature in all Development,' he explained that only from a most +superficial point of view can the various species be looked upon as +permanent and immutable types; that, on the contrary, they can be +nothing but passing stages, or series of stages, of development, which +have been evolved by transformation out of common ancestral forms. + +JOHANNES MUELLER, born at Coblenz in 1801, established himself +as _Privat-docent_ at Bonn, where in 1830 he became Professor of +Physiology. In 1833 he accepted the Chair of Anatomy and Physiology at +Berlin, where he died in 1858. + +He was one of the most distinguished physiologists and comparative +anatomists. By summarizing the labours and discoveries already made in +the field of physiology, by reducing them to order, and abstracting the +general principles, he became the founder of modern physiology. But +he was scarcely less distinguished by his researches in comparative +anatomy. His 'Vergleichende Anatomie der Myxinoiden,' in _Abhandlungen +der Berliner Akademie_, 1835-45, and 'Ueber die Grenzen der Ganoiden' +(_ibid._, 1846), are standard works of lasting value. + +Mueller exercised a stimulative influence as a teacher. Many well-known +men--such as Helmholtz, Gegenbaur, Bruecke the physiologist, Guenther +the zoologist, Virchow the pathologist, Koelliker and Haeckel--have +been his pupils. + +RUDOLPH VIRCHOW was born in 1821 at Schievelbein, a small +town in Eastern Pomerania. He studied medicine in Berlin as a pupil +of Johannes Mueller, and went in 1849 to Wuerzburg, where, under the +influence of Koelliker, and Leydig the pathologist, he laid the +foundation of an entirely new branch of medical science--that of +'cellular pathology.' Since 1856 he has filled the principal Chair of +Pathology at Berlin. In 1892 he received the Copley medal of the Royal +Society. + +'His contributions to the study of morbid anatomy have thrown light +upon the diseases of every part of the body; but the broad and +philosophical view he has taken of the processes of pathology has +done more than his most brilliant observations to make the science of +disease. + +'In pathology, strictly so called, his two great achievements--the +detection of the cellular activity which lies at the bottom of +all morbid as well as normal physiological processes, and the +classification of the important group of new growths on a natural +histological basis--have each of them not only made an epoch in +medicine, but have also been the occasion of fresh extension of science +by other labourers' (Proc. Royal Soc., 1892). + +Virchow has not confined himself to medicine. He takes the keenest +interest in anthropology and ethnology, on which subjects he has +contributed many papers. Together with his colleagues Helmholtz the +physicist, and Du Bois Reymond the physiologist, he has taken a leading +place in the spreading of natural science; but, unfortunately, he +did not take to the doctrine of Evolution, and for the last thirty +years has been its declared antagonist, rarely missing an opportunity +of denouncing everything but descriptive anatomy and zoology as the +unsound speculations of dreamers. This has on more than one occasion +brought him into sharp conflict with Haeckel. His activity is +astonishing, especially if it be remembered that Virchow has for many +years been one of the most conspicuous leaders of the Progressists and +Radicals in the German Parliament and Berlin town-council. + +EDWARD DRINKER COPE was born at Philadelphia, Pa. After studying at +several Continental Universities, especially at Heidelberg, he became +first Professor of Natural Science at Haverford College, and later +Professor of Geology and Mineralogy. He died at an early age in 1897. +As a member of various geological expeditions and other surveys, he +explored chiefly Kansas, Wyoming, and Colorado; and he published many +most suggestive papers on the fossil vertebrate fauna of North America, +and on classification especially of Amphibia and Reptiles. + +Among works of a more general philosophical scope may be mentioned 'The +Origin of the Fittest,' 1887, and his latest work, 'The Primary Factors +of Organic Evolution,' 1896. + +ALBERT VON KOELLIKER, born in 1817, became Professor of Anatomy at +Wuerzburg. His earlier studies and discoveries contributed considerably +to the systematic development of the cell theory. In 1844 he observed +the division and further multiplication of the original egg cell. Next +year he showed the continuity between nerve cells and nerve fibres in +the Vertebrata; later, that the non-striped or smooth muscular tissue +is composed of cellular elements. He demonstrated that the Gregarinae +are unicellular creatures. In 1852 he went with his younger friend +Gegenbaur to Messina, where he studied especially the development +of the Cephalopoda (cuttlefishes and allies); and he produced a +magnificent work on Alcyonaria, Medusae, and other allied forms. He +elucidated the development of the vertebral column, especially with +reference to the notochord. + +In 1848 he founded, together with Th. von Siebold, the famous +_Zeitschrift fuer wissenschaftliche Zoologie_. + +A standard work on mammalian embryology is his 'Entwicklungsgeschichte +des Menschen und der hoeheren Thiere,' a text-book of which the second +edition appeared in 1879. + +At the anniversary meeting of 1897 he received the Copley medal, the +highest honour which the Royal Society can bestow. + +CARL GEGENBAUR was born on August 21, 1826, in Bavaria. He studied +medicine and kindred subjects in Wuerzburg, and as a pupil of Johannes +Mueller in Berlin. + +In 1852 he went with Koelliker to Messina to study the structure and +development of the marine fauna. Important papers on Siphonophora, +Echinoderms, Pteropoda, and, later, Hydrozoa and Mollusca, were the +result. Soon after his return he was offered the chair of Anatomy at +Jena, and at this retired spot he produced his most important works, +devoting himself more and more to the study of the Vertebrata. Since +1875 he has held the Chair of Anatomy at Heidelberg. + +In 1859 he published his 'Principles of Comparative Anatomy'; but in +1870 he remodelled it completely, the theory of descent being the +guiding principle. These 'Grundzuege' were followed by a somewhat more +condensed 'Grundriss,' the second edition of which was published +in 1878, and has been translated into French and English. In the +meantime he had broken new ground by the development and treatment of +certain problems concerning the composition and origin of the limbs, +the shoulder-girdle and the skull, researches which are embodied in +his 'Untersuchungen zur vergleichenden Anatomie der Wirbelthiere,' +1864-65-72. + +In 1883 he brought out a text-book on human anatomy. This also marked +a new epoch, because for the first time, not only the nomenclature, +but also the general treatment of human anatomy, was put upon a firm +comparative anatomical basis. The success of this work is indicated by +the fact that it reached the sixth edition in 1897. + +Lastly, in 1898, appeared the first volume of what may be called his +crowning work, 'Vergleichende Anatomie der Wirbelthiere.' + +Gegenbaur is universally recognised, not only as the greatest living +comparative anatomist, but also as the founder of the modern side of +this science, by having based it on the theory of descent. + +In 1896 he received from the Royal Society the Copley medal 'for +his pre-eminence in the science of comparative anatomy or animal +morphology.' + +His marvellously powerful influence as a teacher and investigator has +made Heidelberg a centre whence many pupils have spread his teaching, +and above all his method of research. + +ERNST HEINRICH HAECKEL was born on February 16, 1834, at Potsdam. He +carried out his academical studies alternately at Berlin and Wuerzburg, +attracted by such men as Johannes Mueller, Koelliker, and Virchow. +For years he was undecided what his career should be, whether that +of botanist, collector, or geographical traveller. Certainly that of +medicine attracted him least, although in deference to his father's +wishes he qualified and settled down for a year's practice in Berlin. +As he himself has told us, he might perhaps have proved rather +successful as a physician, to judge from the fact that he did not lose +a single patient. But 'I had only three patients all told, and the +reason of this is perhaps that I had given on my plate the hours of +consultation as from 5 to 6 _a.m._' + +During the year 1859 he travelled as medical man and artist in Sicily. +In 1861 he was induced by Gegenbaur, whose acquaintance he had made in +Wuerzburg, to establish himself as a _Privat-docent_ for comparative +anatomy in Jena. And there he has remained ever since, filling the +Chair of Zoology, and having declined several much more tempting offers +from the Universities of Wuerzburg, Vienna, Strassburg, and Bonn. + +Within one year, 1865, he wrote the two volumes of his 'Generelle +Morphologie der Organismen,' as he himself relates, in order to master +his sorrow over the loss of his first wife. But he broke down, and went +to the Canaries to recruit health and strength. The 'Morphologie,' +which has long been out of print,[25] made scarcely any impression. It +was ignored, probably because he had placed the old-fashioned study of +zoology and morphology upon a thoroughly Darwinistic basis. + +[25] That this great work is now comparatively rare, although still +in the second-hand market, may perhaps be urged in excuse of the +fact of so many attempts made by many authors, both professional and +amateur, to find fault with or to explain the principles of adaptation, +variation, heredity, caenogenesis, phylogeny, etc., in complete +ignorance that all these and many more fundamental questions were fully +discussed more than thirty years ago in the 'Generelle Morphologie.' + +On the advice of his friend Gegenbaur, he gave a more popularly +written abstract of his 'Generelle Morphologie'--in fact, the +substance of a series of his lectures--in the shape of his 'Natuerliche +Schoepfungsgeschichte.' This 'History of Natural Creation,' which +in 1898 has reached the ninth edition (first edition translated +into English in 1873), had the desired effect. So also had his +'Anthropogenie oder Entwicklungsgeschichte des Menschen,' the fourth +edition of which appeared in 1891. + +It was a lucky coincidence that Haeckel had just finished his +preliminary academical studies, was entirely at leisure, and +undetermined to which branch of natural science he should devote his +genius, when Darwin's great work was given to the world. Haeckel +embraced the new doctrine fervently, and, as Huxley was doing in +England, he spread it and fought for it with ever-increasing vigour in +Germany. + +With marvellous vigour and quickness of perception he applied the +principles of Evolution or the theory of descent to the whole organic +world, and not only opened entirely new vistas for the study of +morphology, but also worked them out and fixed them. He was the first +to draw up pedigrees of the various larger groups of animals and +plants, filling the gaps by fossils or with hypothetical forms (the +necessary existence of which he arrived at by logical deductions); +and thus he reconstructed the first universal pedigree, a gigantic +ancestral tree, from the simple unicellular Amoeba to Man. Of course +these pedigrees were entirely provisional, as he himself has over and +over again avowed; but they are, nevertheless, the ideal which all +systematists and morphologists working upon the basis of Evolution have +since been seeking to establish. + +Naturally he was vigorously attacked, not only by anti-Darwinians, +or rather anti-Evolutionists, but also by many of those who, having +accepted the principle of transformism, ought to have known better. +Perhaps they thought they did know better. Imperfections or mistakes in +details of the grand attempt,--and these, naturally, were many,--were +singled out as samples of the whole, which was ridiculed as the romance +of a dreamer. + +In the end, however, this hostility, narrow-minded and unfair in +many respects, has done good to the cause. There has arisen an +ever-increasing school of workers in favour of the new doctrine. Owing +to renewed research, criticism, corrections in all directions, we +now know considerably more about natural classification (and this is +pedigree) than when Haeckel first opened out the whole problem. + +Owing to his fearless mode of exposition, regardless of the indignant +wrath which the new doctrine aroused in certain ecclesiastical +quarters, Haeckel bore the brunt of almost endless attacks, and had to +write polemical essays. The result has been that friend and foe alike +are now working on the lines which he has laid down; most of the ideas +which he was the first to conceive, and to formulate by inventing a +scientific terminology for them, have become important branches, or +even disciplines, of the science. + +Most morphologists of the younger generations now take these terms +for granted, without remembering the name of their founder. It is, +therefore, perhaps not quite superfluous to mention some of them: + +_Phylum_, or stem, the sum total of all those organisms which have +probably descended from one common lower form. He distinguished eight +such phyla--Protozoa, Coelenterata, Helminthes or Vermes, Tunicata, +Mollusca, Articulata, and Vertebrata. The phyla are more or less +analogous to 'super-classes,' large branches or 'circles,' or principal +groups of other zoologists. + +_Phylogeny_, the history of the development of these various phyla, +classes, orders, families, and species. + +_Ontogeny_, the history or study of the development of the individual, +generally called embryology. In reality the scope of embryology +is the ontogenetic study of the various species, and this branch +of developmental study alone can be checked by direct, 'exact' +observation, for the simple reason that the individuals alone are +entities, while the species, genera, families, etc., are abstract ideas. + +The _ontogenesis of any given living organism is a short, condensed +recapitulation of its ancestral history or of its phylogenesis_. This +is Haeckel's 'fundamental biogenetic law.' + +A complete proof of the phylogeny of any creature would be given by +the preservation of an unbroken series of all its fossil ancestors. +Such a series will in most cases, for obvious reasons, always remain a +desideratum. In a few cases, however, the desideratum is nearly met: +for example, the ancestral line of the one-toed digitigrade horse from +a four-or five-toed plantigrade and still very generalized Ungulate is +approaching completion. + +Phylogenetic study has to rely upon other help. This is afforded by +comparative anatomy and by the study of ontogeny. If the latter were +a faithful, unbroken recapitulation of all the stages through which +the ancestors have passed, the whole matter would be very simple; but +we know for certain that in the individual development many stages +are left out (or, rather, are hurried through, and are so condensed +by short-cuts being taken that we cannot observe them), while other +features which have been introduced obscure, and occasionally modify +beyond recognition, the original course. + +Again, the sequence of the appearance of the various organs is +frequently upset (_heterochronism_). Some organs are accelerated in +their development, while others, which we know to be phylogenetically +older, are retarded in making their reappearance in the embryo. + +These disturbing or distorting newly introduced features or factors +show themselves chiefly in connection with the embryonic conditions of +growth--for example, yolk-sac, placenta, amnion. They all come within +the category of _caenogenesis_: they are caenogenetic, while the true, +undisturbed recapitulation is _palingenetic_. + +Lastly, some features, so-called rudimentary or vestigial organs, +instead of disappearing, are most tenacious in their recurrence, +while others of originally fundamental importance scarcely leave +recognisable traces, and are, so to speak, only hinted at during the +embryonic growth of the creature we happen to study. Hence arises the +philosophical study of 'Dysteleology.' + +Among other terms invented by Haeckel, and now in general use, are +_Metamere_, _Metamerism_, _Coelom_, _Gonochorism_, _Gastrula_, +_Metazoa_, _Gnathostomata_, _Acrania_, _Craniota_, and _Amniota_. + +Hitherto we have dealt with his general work only, a resume of which +he gave for many years in a course of thirty lectures before an +audience composed of 'all sorts and conditions of men.' Students of +biology and of medicine side by side with theologians, incipient and +ordained, jurists, political economists, and philosophers, crowded his +lecture-room during the 'seventies to hear the master explaining the +'natural history of creation' or the mysteries of anthropogenesis. +Another course of eighty lectures during the winter semester was, and +still is, devoted to a systematic treatment of zoology, while practical +classes are reserved for the more select. + +His winning personality and fascinating eloquence, combined with a +clear and concise delivery, have gained the enthusiastic admiration of +many a student who went to the quiet University town in order to learn +with his own ears and eyes. + +_List of Separate Publications by Professor Haeckel._ + +'Biologische Studien. I.: Studien ueber die Moneren und andere +Protisten.' Leipzig, 1870 (out of print). He was the first to +make observations on the natural history of the Monera, living +bits of protoplasm, devoid even of a nucleus--_e.g._, _Protogenes +primordialis_, _Protomyxa aurantiaca_. + +'Monographie der Radiolarien.' Berlin, 1862-88. With 171 plates. + +'Entwicklungsgeschichte der Siphonophoren.' Utrecht, 1869. + +'Plankton-Studien. Vergleichende Untersuchungen ueber die Bedeutung und +Zusammensetzung der pelagischen Fauna und Flora.' Jena, 1880. + +'Metagenesis und Hypogenesis von Aurelia aurita.' Jena, 1881. + +'Monographie der Geryoniden oder Ruesselquallen.' Leipzig, 1865. + +'Generelle Morphologie der Organismen.' 2 vols. Berlin, 1866. + +'Anthropogenie oder Entwicklungsgeschichte des Menschen,' 1874; 4th +edition, 1891. + +'Natuerliche Schoepfungs-Geschichte.' 2 vols. Berlin, 1st edition, +1868; 9th edition, 1898. This work has been translated into most +European languages (the first edition in English, under the title +'Natural History of Creation' in 1873; the eighth in 1892). + +'Monographie der Kalkschwaemme.' 3 vols. Berlin, 1872 (out of print). +With the subtitle, 'An Attempt to solve analytically the Problem of +the Origin of Species.' In this work, illustrated by sixty plates, he +showed that the Calcispongia are individually so yielding, so adaptive +to external influences, that it is practically impossible to break up +the whole group into anything like satisfactory species or genera. +According to predilection, we can distinguish either 1 genus with only +3 species, or 3, 21, 43 genera, with 21, 111, 181, or 289 species +respectively. + +In this work, in 1872, Haeckel established the homology of the two +primary layers, ecto- and endoderm, throughout the Metazoa. The attempt +to do the same for the four secondary layers, as made in the second +part of his 'Gastraea-theory,' failed. It caused an enormous amount of +research, hitherto without a satisfactory solution of the problem. + +'Studien zur Gastraea-Theorie.' Jena, 1874. The transformation of +the single primitive egg-cell by cleavage into a globular mass of +cells (Morula)--which latter, becoming hollow (and then known as the +Blastula), turns ultimately by invagination or by delamination into +the Gastrula--is a series of processes which applies to all Metazoa. +The Gastrula is, therefore, the ancestral form of the Metazoa; and the +Gastraea-theory, founded by Haeckel, throws light, on the one hand, upon +the mystery of the phyletic connection of the various animal groups, +while, on the other hand, it connects the Metazoa, or multicellular +organisms, with the lowest Protozoa. We come to this conclusion +becaues the Gastrula arises from and passes through stages which exist as +independent, permanent organisms among the Protozoa. + +Needless to say this Gastraea-theory has been violently attacked in +detail, with the result that various modifications of the Gastrula, +until then undreamed of, have become known. + +'Monographie der Medusen.' Jena, 1879-81. With 72 coloured plates. + +'Reports on the Scientific Results of the Voyage of H.M.S. +_Challenger_.' With 230 plates: + + 1. Deep-sea Medusae. 1881. + 2. Radiolaria. 1887. + 3. Siphonophorae. 1888. + 4. Deep-sea Keratosa. 1889. + +A short holiday spent on the coasts of the Red Sea produced the volume +'Arabische Korallen' (Berlin, 1876); and a longer trip to Ceylon has +been described in 'Indische Reisebriefe,' of which the third edition +appeared in 1893. The English translation (1883) is entitled 'A Visit +to Ceylon.' + +'Monism as connecting Religion and Science: the Confession of Faith of +a Man of Science.' 1894. + +Haeckels latest work is the 'Systematische Phylogenie' (Berlin, 1896), +three volumes dealing with Protistae and Plants, Invertebrata and +Vertebrata. They contain the author's views on the natural system of +the organic world, both living and extinct. Notable in the work are +the many reconstructions of ancestral forms which, provided Evolution +is true, must have existed--hypothetical until they, or something like +them, are found in a fossil state. Everybody who works systematically, +and upon the basis of Evolution, does, sometimes unconsciously, +reconstruct such links, although he may perhaps not see the necessity, +or have the courage to fix his vision, by assigning to it all those +attributes or characters which are indicated by deductions from +comparative anatomy, palaeontology, and embryology. + + + + + THEORY OF CELLS. + + +The vegetable cell was discovered by _Schleiden_, Professor of Botany +at Jena, in 1838. Next year _Schwann_ found the animal cell. + +In 1844 _Koelliker_ discovered that the egg cell, by division and +multiplication, becomes an aggregation--a heap of new cells. + +In 1849 _Huxley_ found the two primary layers (observed long before +by _Pander_ and _Baer_ in the chick) also in certain Invertebrata, +the Medusae; and he called these layers 'ectoderm' and 'endoderm' +respectively. + +In 1851 _Remak_, in his 'Untersuchungen ueber die Entwicklung der +Thiere,' showed the egg to be a simple cell, and that from it, by +repeated division or multiplication, arise the germinal layers, and +that by differentiation of the cells of these layers are formed all the +tissues of the body. + +_Kowalevsky_, of St. Petersburg, found the two primary germinal layers +also in Worms, Echinoderms, Articulata, and other animals. + +_Haeckel_, in 1872, found the same in the Sponges. He stated that these +two germinal layers occur in all animals, except in the Protozoa; +and that they are homologous, or equivalent, in all the groups of +animals, from the Sponges up to Man. In 1873, in his 'Gastraea-theorie,' +he explained the phylogenetic significance, and tried to show the +homology, of the four secondary germinal layers. + + + + + FACTORS OF EVOLUTION. + + +An organism, as living matter, does not stand in opposition to, +or outside of, the rest of the world. It is part of the world. It +receives matter from its surroundings, and gives some back; therefore +it is influenced by its surroundings. It is acted upon, and it reacts +upon the latter, and if these change (and they are nowhere and never +strictly the same) the organism also _varies_. It _adapts_ itself, and +if it does not, or, rather, cannot, do so, it dies, because it is unfit +to live in the world, or, rather, in those particular surroundings +and conditions in which it happens to be. That organism which yields +most easily, accommodates itself most quickly, has the best chance of +existence--_survival of the fittest_. 'Fitness' in this case does not +mean fitness to live, but rather a particular condition which happens +to fit into the new circumstances. + +Adaptation and variation are simultaneous: they are fundamentally the +same. If there were no adaptability and no variability, those simplest +of organisms which we suppose to have sprung into existence in the +pre-Cambrian period would long ago have ceased to exist. + +It is the physiological momentum which models the organism, and, by +causing its adaptations, has produced its organs by change of function. +Gegenbaur illustrates this most important fundamental truth by an +excellent example. Suppose that, in an absolutely simple organism, all +the parts of its exterior are under the same functional conditions, +so that each part of the surface can take in food, and that this is +digested, assimilated, in the interior. There is, in this condition, +not yet any definite organ. If this organism sinks to the bottom and +becomes sessile, this part is excluded from taking in nourishing +matter, while the opposite surface alone remains, or becomes more, fit +for this function. Thus, a simple variation and adaptation has been +produced, and if the same organism continues in this position, its +bottom cells will estrange themselves from their original function, +while those on the top will convey the food into the interior, where +a cavity will be formed, ultimately with a permanent opening, the +primitive gut and mouth, both very different from the 'foot.' + +Thus, by adaptation and variation the organism acquires new functions, +organs, features, and it gives up and eventually loses others. Its +offspring is like it. Like produces like. This is the principle of +_heredity_. Adaptation, when going on generation after generation on +the same lines in the same direction, becomes continuous, and has an +intensifying, _cumulative_ effect. By always weeding out from a flock +of pigeons those birds which possess more dark feathers than the rest, +we ultimately produce an entirely white race. We hurry on what Nature +does slowly. + +The inheritance of acquired characters becomes very obvious in the +following example: The Monera are the lowest living organisms known; +they consist of a mass of protoplasm, and are still devoid of even +a nucleus. They multiply simply by division; each half is like the +other, and like the parent (which by this process has ceased to exist), +except that each is smaller and has to grow. A certain Moneron, +_Protomyxa aurantiaca_, is orange-coloured, and its offspring is from +the beginning of the same colour, and this colour has been acquired +by that kind of Monera-like protoplasm which thereby has become the +species called Aurantiaca. We have no reason for assuming that there +existed from the beginning of life not only colourless, but also red, +orange, and other kinds of protoplasm. In these simplest of organisms +the whole process of heredity seems very obvious; but in the higher +ones, in those which propagate by eggs, the problem is infinitely +more complicated. It is true that the egg is, strictly, nothing but +a small part of the parental organism, and we know from everyday +experience that this single egg-cell has in it all the attributes and +characteristics of the parent; but these attributes and characteristics +make their appearance successively, just as the egg cell of a chick has +neither wings nor feathers, not even a backbone, but develops these +organs because its parents have them. + +The theory that acquired characters are hereditary has often been +vigorously attacked; but the champions of the negative position have +not given us anything satisfactory instead. They question, also, the +principle of adaptation as a factor in Evolution, and substitute +'variation,' coupled with 'natural selection.' + +They point to Darwin's argument: (1) It is a fact that animals and +plants produce a much greater number of young than in their turn grow +up to propagate the race; (2) no two of the frequently many individuals +of the same breed are exactly alike, although the differences may be +hidden to our perception (this is quite true, because no two entities +can live in absolutely the same place and conditions); (3) through +heredity the offspring takes over the faculties and features of the +parents; (4) what decides which of the many individuals (each one +possessing some aberration or variation) are to live and to propagate +the race?--obviously those individual variations which happen to make +the lucky possessors most fit for the struggle for life. + +So far, well; but the 'Neo-Darwinians' imagine that 'adaptation' +is not the cause, but the result, the effect, of the formation of +species. According to them, the species are neither adapted by, nor do +they adapt themselves to, their surroundings. Adaptation is to them +an accomplished fact, a condition which a species happens to be in +because its particular variation is the one which, to the exclusion of +others, suits or fits into its surroundings. Such a view simply takes +variation for granted, and stipulates it as a something _a priori_, +without raising the further necessary question, why there should be +any variations at all. Why, indeed, unless they are caused by external +influences? Haeckel elucidated this by the conception of adaptation as +explained in the foregoing pages. + +These and kindred speculations have produced some rather curious +discussions, which not infrequently end in conundrums. If we speak of +a case of adaptation as a condition, a fact, we easily run the risk +of getting into confusion about cause and effect. For example: Is the +stag swift because he has long and slender legs, or are his legs long +because he is swift? In reality, swiftness and length of legs are cause +and effect in one. His legs have been so modified as to make him swift, +because he has put them continuously to whatever was his full speed, +which in his thick-footed ancestors was probably a very slow one. The +above question reads, therefore, more sensibly as follows: Has the stag +become swift because his legs have become long and slender, or have his +legs become long and slender because he has attained swiftness? Now, we +see that both halves of the double question are practically the same +and instantly suggest the answer. + +A fundamental difference between artificial machines and living +organisms is that the former are worn out by use, while the latter not +only repair the loss caused by use, but are also stimulated to further +increase. On the other hand, organs which are not put into function, +or are not used, _degenerate_. The various cells of the organ react +upon external stimuli by increased activity. Why this should be so is +another question--perhaps because those which do not would soon be not +fit to survive. Each cell has a function; the more specialized the more +intense it is. Every external stimulus, every contact with the outer +surroundings, is an insult, necessarily of detrimental effect, as it +disturbs the equilibrium of the cell body. It must, therefore, be of +advantage to the cells' well-being to return as soon as possible to the +_status quo ante_, and this can only be done by increased activity. + +In the present state of our knowledge, we can approach only the +simplest cases of acquisition of characteristics. Mostly they are +so complicated, subject to so many unthought-of conditions, that we +do not know from which end to approach the problem. Frequently the +supposed use of certain obvious features is the merest guesswork. This +applies especially to features to which we are not accustomed (although +wrongly so) to assign a function--for example, coloration. A green +tree-frog will with predilection rest on green leaves. The advantages +of concealment are obvious, and in this case he 'adapts himself' to the +surroundings by making for green localities: if he did not he would +be eaten up sooner than his more circumspect comrades. But this making +for, and sitting in, the green has not _necessarily_ made him of that +colour. Extreme advocates of one view would argue as follows: Once upon +a time there were among the offspring of ancestral tree-frogs some +which, among other colours, exhibited green, not much, perhaps not even +perceptible to our eyes. The occurrence of this colour, according to +them, was spontaneous, a freak--as if in reality there were anything +spontaneous in the sense of being causeless. The descendants of these +more greenish creatures, provided they did not pair with frogs of the +ordinary set, became still greener (by accumulative inheritance), and +so on, until the green was pronounced sufficient to be of advantage +when competition could set in. + +With this view there is always the difficulty of understanding how the +initial very small changes can be useful, unless we have to deal with +extremely simple organisms. Is it likely in the case of our frogs that +an almost imperceptible variation in colour makes them more fit to +live? We have to assume that 'luck' or chance kept them for generations +out of harm's reach, until the accumulation of green, hitherto quite +ineffective, neither harmful nor useful, became strong enough to be +effective. Such cases undoubtedly happen. + +But we can also argue out this problem in a somewhat different way, +which goes nearer to the root of the whole process. The original +slight, imperceptible change in pigmentation is not a spontaneous +freak; it was caused by the direct influence of the surroundings in +which the particular frogs happened to live, be this factor light or +temperature or food. Thus it stands to reason that the offspring, +living under similar conditions, will be acted upon in the same way. +That factor which has added green to the parents will add green to the +children, until by accumulative inheritance a more decidedly green +race is produced. + +The offspring of green plants do not become green when grown in the +dark; the young plants inherit not the green, but the capacity of +becoming green when acted upon by sunlight. This as an instance of +direct influence of the surroundings on a substance (chlorophyll), +which has not yet performed a function. But the kittens of a pair of +black cats produce black hair before they are born, and we have no +reason to doubt that the black pigment in their tegumentary structures +is ultimately referable to the action of the sunlight. In many +instances creatures living for generations in darkness become white, +pigmentless, and they regain it when exposed to light. For example, the +white, colourless Proteus from the caves of Adelsberg becomes clouded +grey, and ultimately jet black, when kept in a tank whence light is not +strictly excluded. + +Blindness is a very general characteristic of creatures which dwell in +darkness. There are all stages between total blindness and weak eyes. +Now, do these blind creatures live in darkness because they are blind, +or have they become first weak-eyed and then blind because of the +continuous disuse of their eyes? The former explanation has actually +been suggested! Individuals not smitten, but spontaneously, as a freak, +born with sore eyes, have crept into the darkness for relief and have +produced a blind race! To carry such a notion to the bitter end leads +to absurdities. Anyhow, it is not understandable where the benefit +of losing the eyesight arises. It can be explained only by continued +disuse: witness _Spalax typhlus_, the blind mole, and, above all, the +Endoparasites. + +Let us now take an example to explain the influence of a tangible +external stimulus. Repeated pressure produces callosities. Although +they are not exactly beneficial in the shape of corns on our toes, +they are so on our hands. At any rate, the morphologist can trace the +development of the footpads, nails, hoofs, and horns, step by step from +small beginnings. The cells of the Malpighian stratum, of the inner, +active portion of our epidermis, are excited to extra activity, and +by continually producing more horn cells than peel off the surface of +the skin in the normal process of wear and tear cause the formation +of the pad. It need scarcely be mentioned that hypertrophic growths +are not necessarily useful; they are often harmful, and in that case +pathological. + +Lastly, a few words about the very difficult question of _teleology_. +In trying to explain Evolution in a mechanical--sometimes called +monistic, but in reality natural--way, we exclude anything like a +set purpose, a goal, or ideal, a final condition which the organism +strives to attain. Unknown, however, to many morphologists, especially +embryologists, their writings are full of this teleological notion. +Indeed, there are many cases in which an organism becomes changed, and +quickly, too, in a way which cannot but be called reasonable. It starts +modifications, be they outgrowths, alterations in shape or colour, or +the making good of injuries received, which by 'short-cuts' produce +the only advantageous result that can reasonably satisfy the new +requirement or altered circumstances. + +Trees growing in precarious positions, after part of the supporting +rock has slipped away, throw out new roots, and rearrange some of +the old ones in the only way which could save the tree. In animals +which have lost part of a limb the wound closes up, and what is left +is turned into a serviceable stump--for example, in water-tortoises +(creatures in which reproduction of lost limbs does not happen). In +frogs and newts the lost part is reproduced, not correctly, but in a +good semblance. Tortoises which have had their shell smashed can throw +off an astonishingly large portion and renew the bone as well as the +overlapping scutes; but this mending is not neatly done. It serves the +requirement, but it is patchwork; the new shell is such as no tortoise +ever possessed before. + +Mammals transported into colder countries, or subjected to continued +exposure, grow a thicker coat; and the same kind of tree which in a +sheltered valley is tall, large-leaved, and soft-wooded, assumes a very +different aspect, although perhaps growing into a healthy specimen, +when planted on a wind-exposed hill. + +There is no room, or, rather, no time, to apply to these cases the +principle of many variations or the long-continued accumulation of +infinitely small changes. The thing is to be done quickly, or not +at all. Nor can we explain the mending of a wound, which implies an +activity of countless cells, simply as a case of, or similar to, the +reproduction of a lost part; against such an explanation militates the +almost absolute unlikelihood of that precise injury having happened +before to any of the creature's ancestors. + +Still, I think we are brought near the solution of the mystery by +such considerations. We see no difficulty in the regeneration of a +few cells, or in the making good of the disturbance suffered by one +of the most simple organisms; but we become suspicious when we see +that countless cells, not of one kind, but of the most varied tissues +and parts of the body, make common cause in remedying a defect in a +serviceable way. + +We must assume that since the beginning of life organisms have been +subjected to countless insults. We can scarcely speak of a wound in +an Amaeba; but these insults have always been made good, and whenever +this was not the case, that particular organism came to an end. As +these organisms developed into more complicated ones, the possible +insults became more serious, more complicated; and the organisms took +adaptive measures so as to be superior to them. This action, I have +no hesitation in declaring, became by heredity a habit. The whole +creature became so thoroughly 'imbued' (for want of a better word) with +the finding of ways and means for meeting sudden, serious conditions, +that it now acts directly, and produces by a short-cut, with the least +amount of time and with the smallest possible waste of material, that +which meets the occasion, thereby saving the life of the individual +and that of the race. This we cannot but call reasonable and to the +purpose, although it is all carried out by _causae efficientes_ without +there being any _causae finales_. + + + + + GEOLOGICAL TIME AND EVOLUTION. + + +One million years is a stretch of time beyond our conception. We can +arrive at a more or less adequate understanding of what a million +individuals or concrete things means. Several Continental nations +can put more than a million men into the field. We can gaze at a +building which contains as many bricks; and we know that our own body +is composed of millions of millions of cells. No such help applies to +time, because that itself is an entirely relative, abstract conception. +We can imagine what one hundred years are like--a span of time +seemingly short to the hale and hearty octogenarian, enormous to the +child, totally inapplicable to certain animals whose whole life is +crowded into one single day. + +Astronomers have long ceased to reckon distances by miles or any +other understandable unit. They express the distances between us and +the stars and nebulae by 'years of light.' Try to imagine a unit of +length equal to that which is passed through by light (186,000 miles +per second) in one year. Not so very long ago the enormous distances +resulting from astronomical calculations were looked upon as the most +serious objection to the correctness of the astronomers' views as to +the distances which separate our globe from the nearest fixed stars. +We have not yet accustomed ourselves to reckoning time by some similar +broadly-conceived standard--say aeons of so many thousand years each. + +Unfortunately, we possess no data whatever for calculating the age +of the successive geological strata. Thanks to Lyell, the theory of +violent universal cataclysms has been done away with. It is more +probable that the same agencies have acted which are now changing +the aspect of the globe; and these changes are slow, as far as we +know them--at least, as far as the formation of sedimentary strata is +concerned, and these alone we have to deal with. Various calculations +have been made, based upon the denudation of the mountains, the +filling up of the valleys by the debris, the formation of deltas, +etc. The results give enormous stretches of time, but all of them +unsatisfactory, because the methods are so very local in their +application. + +The least objectionable attempt is that which, based upon astronomical +calculations, tried to fix the height of the last Glacial epoch[26] at +about 200,000 years ago, and asserted that since its beginning in the +Pliocene epoch as many as 270,000 years have elapsed. The duration +of the whole Tertiary period has by the same authorities been fixed +approximately at 3,000,000 to 4,000,000 years. Beyond this we cannot +venture without the wildest speculation; but we know to a certain +extent the thickness of the various sedimentary strata, which amount +in all to from 100,000 to 175,000 feet--on the average perhaps 130,000 +feet, or about twenty miles. + + [26] James Croll: 'On Geological Time, and the Probable Date of the + Glacial and Upper Miocene Period,' _Philos. Magazine_, xxxv., 1868, pp. + 363-384; xxxvi., pp. 141-154; 362-386. + +Unless we prefer giving up all attempt at calculation as absolutely +hopeless, and thus resign the whole problem, we must at least try to +arrive at some results, and then see if these cannot reasonably be made +use of. + +Neither geologist nor physicist, and no zoologist, would accept the +suggestion that these 130,000 feet of stratified rocks have been +deposited within only as many years, although the average rate of +deposit would in that case be not more than 1 foot per year. On the +other hand, an indignant protest is raised against the assumption of +1,000,000,000 years. + +Lord Kelvin[27] has come to the conclusion (from data which various +other authorities regard as very unsatisfactory) that not much more +than 100,000,000 years can have elapsed since the molten globe acquired +a consolidated crust. Further time must have passed before the surface +had become stable and cool enough to allow the temperature of the +collecting oceans to fall below boiling-point, and it is obvious that +life cannot possibly have begun until after this had happened. + + [27] William Thomson: 'On the Secular Cooling of the Earth,' _Transact. + R. S. Edinb._, xxiii., 1864, pp. 157-169. + +Wallace, in his 'Island Life,' by making use of Professor A. Geikie's +results as to the rate of denudation of matter by rivers from the +area of their basins, and estimating the average rate of deposition, +concludes that 'the time required to produce this thickness of rock +[Professor Haughton's maximum of 177,000 feet] at the present rate +of denudation and deposition is only 28,000,000 years.' Our lower +assumption of 130,000 feet thickness would give only 20,000,000 +years--a rate of 1 foot in 154 years. + +Again, if we prefer round numbers to start with, we have only to +assume that the age of the whole Tertiary period, with its 3,000 feet +thickness, is 3,000,000 years (_i.e._, 1,000 feet in 1,000,000 years, +or 1 foot in 1,000 years, surely an excessively slow rate); then +130,000,000 years would bring us to the bottom of the Laurentian or +pre-Cambrian deposits. Of course, it is a pure assumption that the +same rate of destruction and sedimentation applies to the whole of the +strata; but we know nothing to the contrary, especially if we consider +the average periods, the quick periods of extra activity, taken with +the slow periods or those of standstill. + +Dana estimated the length of the whole Tertiary period at one-fifteenth +of the Mesozoic and Palaeozoic combined. If we take the duration of the +Tertiary period, as before, as 3,000,000 to 4,000,000 years, the total +will amount to from 45,000,000 to 60,000,000 years. + +Lastly, Walcott[28] has estimated the duration of the Palaeozoic, +Mesozoic, and Caenozoic or Tertiary epochs at about 17,000,000, +7,000,000 and 3,000,000 years respectively, giving 27,700,000 years +from the beginning of the Cambrian; and Williams[29] has calculated the +relative duration of the smaller epochs. See the table on p. 149. + +The results of all these calculations fall surprisingly well within +the limits of Lord Kelvin's allowance. Of course they are based upon +assumptions, but none of them is inherently unreasonable; and it +was my purpose to draw attention to the surprising coincidence in +the closeness of these results, perhaps too good to be true. Such +calculations are considered close enough if they range within a few +multiples of each other. + + [28] 'Geological Time as indicated by the Sedimentary Rocks of North + America.' _Proc. Amer. Assoc. Adv. Sci._, xlii., 1893, pp. 129-169. + + [29] Henry Shaler Williams, 'Geological Biology.' New York, 1895. + +Zoologists have fallen into the habit of requiring enormous lengths of +time for the evolution of the animal kingdom. We know that Evolution is +at best a slow process, and the conception of the changes necessary to +evolve man from monkey-like creatures, these from the lowest imaginary +mammals, these from some reptilian stock, thence descending to Dipnoan +fish-like creatures, and so on back into Invertebrata, down to the +simple Monera--this conception is indeed gigantic. Innumerable, almost +endless, slow changes require seemingly unlimited time, and as time is +endless, why not draw upon it _ad libitum_? + +Huxley pointed out that it took nearly the whole of the Tertiary epoch +to produce the horse out of the four-toed Eohippos, and that, if we +apply this rate to the rest of its pedigree, enormous times would +be required. This is, however, a very misleading statement, which +necessitates considerable reduction, in conformity with our increased +palaeontological knowledge. Animals of the genus Equus--namely, +Ungulata, with one toe, and with a certain tooth pattern--from the +Upper Miocene of India are now known. Moreover, it is not simply a +question of the gradual loss of the side-toes. The change from the +fox-sized little Eohippos and Hyracotherium, so far as skull, teeth, +vertebral column, and limbs are concerned (about the soft parts we know +next to nothing), is a very great one indeed. + +Elephants and mammoths seem to have developed very rapidly. None are +known from Eocene strata; but towards the end of the Miocene they had +spread over Asia, Europe, and North America, and that in great numbers. +The Eocene Amblypoda are still so different that we hesitate to connect +them ancestrally with the elephants. + +The Pinnipedia (seals and walruses) are strongly modified fissiped +Carnivora, and have existed since at least the Upper Miocene; the +transformation must have been accomplished within the Miocene period. + +We cannot shut our eyes to the fact that various groups have from the +time of their first appearance burst out into an exuberant growth of +modifications in form, size, and numbers, into all possible--and one +might almost say impossible--shapes; and they have done this within +comparatively short periods, after which they have died out not less +rapidly. It seems almost as if these go-ahead creatures had, by +accepting every possible modification and carrying the same to the +extreme, too quickly exhausted their plasticity--which, after all, +must have limits--thereby becoming unable to meet successfully the +requirements of further changes in their surroundings. The slowly +developing groups, keeping within main lines of Evolution, and not +being tempted into aberrant side-issues, had, after all, a much better +chance of onward evolution. + +A good example of the former are the Dinosaurs. We do not know +their ancestors; but we have here to deal only with their range of +transformation. The oldest known forms occur in the Upper Trias; they +attain their most stupendous development in the Upper Jurassic and in +the Wealden; and they have died out with the Cretaceous epoch. But +already some of their earliest forms had assumed bipedal gait, and the +Oolitic Compsognathus had developed almost bird-like hind-limbs. + +On the other hand, there are many instances of extremely slow +development--facts which raise the difficult question of 'persistent +types.' Are these due to a state of perfection which cannot be improved +upon? Or are they due to a kind of morphological consolidation (not +necessarily specialization) which can no longer yield easily, so that +therefore through changes in their surroundings they may come to an end +sooner than more plastic groups? + +Struthio, the ostrich; Orycteropus, the Cape ant-eater; Tapirus, and +many others, existed in the Miocene age practically as they are +now; but pre-Pliocene dolphins, cats, monkeys, stags, all belong to +closely-allied and well-defined 'genera,' but different from the living +forms. + +Alligators and crocodiles are known from the Upper Chalk; Tomistoma +since the Miocene; Gavialis since the Pliocene. + +The oldest surviving reptile is Sphenodon, the Hatteria of New Zealand, +a fair representative of what generalized reptiles of the later +Triassic period seem to have been like; and to the same period belongs +Ceratodus, the Australian mud-fish, hitherto the oldest known surviving +genus of a very ancient and low type so far as Vertebrata are concerned. + +Now let us see if the above estimates of geological time are so utterly +inapplicable to animal evolution. On purpose we take one of the lowest +estimates, about 28,000,000 years, and apportion them equally to the +various strata or epochs. + +The original owner of the famous Trinil skull, a _Pithecanthropus +erectus_, lived, according to some, in the Late Pliocene, according +to others in the Early Plistocene, period--that is to say, somewhere +about the beginning of our last Glacial epoch, some 270,000 years ago. +Assuming that he and his like reached puberty at sixteen to twenty +years of age, about 17,000 generations would lie between him and +ourselves, or, to put it more forcibly, between him and the lowest +living human races--say the Ceylonese Veddahs. Only 250 generations, +at twenty years, carry us back to 3000 B.C. (_i.e._, beyond +the ken of history); and if it be objected that the differences between +the oldest inhabitants of Egypt, the Naquada, and the present Fellahin +are very slight, we are welcome to multiply these differences sixty +or seventy fold, in order to arrive at the Pithecanthropus level. +But these Naquada had no metal implements, and there cannot be the +slightest doubt that the development of the human race went on by leaps +and bounds after certain discoveries had been made--to wit, the use +of implements and that of fire. That creature which first took up a +stone or a branch and wielded it thereby got such an enormous advantage +over his fellow-creatures that his mental and bodily development went +on apace. The same applies to the improvement of speech. We assume the +single, monophyletic origin of mankind at one place, in one district; +and the differences between some of the races of man are great enough +to constitute what we might call species. Compare the Venus of Milo, +that noble expression of the ancient Greeks' notion of female beauty, +with the 'products of art' of the Veddahs or the dwarfs of Central +Africa, or think of the beau-ideal which a Michael Angelo could +possibly have evolved if he had never seen any but such people. + + _TIME AND EVOLUTION_ + + ====================================================================== + I. |II.| III. | IV. | V. |VI.| VII. + | | | | | |Generations. + -----------+---+-----------+----------+--------------+---+------------ + |} |} |} |Adam and Eve | | 250 + Recent |} 5|} |} |Man, contem- | | 3,500 + Plistocene |} |} |} 270,000| porary with | | + | |} |} | Reindeer | | + | |} |} | in France | | + Pliocene -|} |} 3,000,000| |_Pithecanthro-| 16| 17,000 + |} |} |} 600,000| pus erectus_| | + Miocene -|}10|} |} |Anthropoid | 10| 60,000 + |} |} |}2,100,000| Apes | | + Eocene -|} |} |} |Lemures | 5| 420,000 + | | | | | | + Cretaceous | 10|} | 3,600,000| | | + Jurassic - | 5|} | 1,800,000| | | + Rhaetic -|} |} |} |Prototheria, | 3| 1,800,000 + |} |} |} | or first | | + |} |} 7,200,000|} | Mammalia | | + Keuper -|} |} |}1,800,000| | | + Muschel- |} 5|} |} | | | + kalk |} |} |} | | | + New Red |} |} |} |Theromorpha | 4| 425,000 + Sandstone| | | | | | + Magnesian |} |} |} | | | + Limestone|} |} |} | | | + Lower Red |} |} |} |Proreptilia | 4| 250,000 + Sandstone|} |} |}4,000,000| | | + Coal- |}15|} |} |Eotetrapoda | 4| 500,000 + measures |} |} |} | | | + Mountain |} |}17,500,000|} | | | + Limestone | |} | | | | + Devonian -| 15|} | 4,000,000|Dipnoi and | 5| 1,000,000 + | |} | |Crossopterygii| | + Silurian -| 10|} | 2,700,000|First fishlike| 3| 900,000 + | |} | | creatures | | + Ordovician | 10|} | 2,700,000| | | + Cambrian -| 15|} | 4,000,000| Sum total of| | + Laurentian | | | | generations| | --------- + Archaean | | | | (about) | | 5,375,000 + or Meta- | | | | | | + morphic | | | | | | + ====================================================================== + +EXPLANATION OF THE TABLE ON P. 149. + + Column I. contains the names of the successive sedimentary strata. + + " II. contains the percentage of the duration of the various epochs, + according to _Williams_, the time from the Cambrian until recent times + being taken as 100. + + " III. gives the estimated duration in years of the Palaeozoic, + Mesozoic, and Caenozoic periods, according to _Walcott_. + + " IV. gives in years the duration of the various smaller epochs, as + computed from Walcott and Williams' statements. + + " V. Representatives of stages of the ancestral line of man. The + names stand in the level of the stratum in which they have made their + first appearance. + + " VI. contains the number of years which, in the present + calculation, have been assumed necessary for the animal to reach + puberty. + + " VII. contains the number of generations which can have elapsed + from stage to stage. For example, 60,000 generations separate the + earliest known anthropoid apes from Pithecanthropus. + +Let us follow the descent of man further back. The next stage, +reckoning backwards, is that from Pithecanthropus to _bona-fide_ +anthropoid apes. They are represented in the Miocene by various +genera--_e.g._, Pliopithecus and Dryopithecus. According to Croll and +Wallace, 850,000 years ago carry us into the Miocene epoch. Assuming +that these apes lived about 600,000 years before Pithecanthropus, +namely, in the later half of the Miocene, and taking puberty at ten +years of age, a high estimate, we get not less than 60,000 generations. + +2. From Apes back to lowest Lemurs in the lowest Eocene. The date of +Eocene being fixed at 3,000,000, we have about 2,100,000 years for this +stage; assuming as much as five years for puberty, this results in +420,000 generations. + +3. From Lemures to Prototheria. The earliest known mammalian remains +come from the Rhaetic, or top formation of the Triassic epoch; allowing +for the Rhaetic only 100,000 years, we have to add the whole of the +Jurassic and Cretaceous, in all about 5,500,000 years. Assuming three +years for a generation, we get 1,800,000 generations. + +4. From Prototheria to something like the Theromorpha at the bottom of +the Triassic strata. A duration of 1,700,000 years divided by four +gives 425,000 generations. + +5. From Theromorpha to Proreptilia, represented by Eryops and Cricotus +from the Lower Permian of Texas. Allowing 1,000,000 years, each +generation at four years, we obtain 250,000 generations. + +6. From Proreptilia to Eotetrapoda, the first terrestrial Vertebrata, +represented by something like the Stegocephali, the earliest of which +are known from the Coal-measures. Assuming them to have come into +existence at the bottom of the Coal-measures, for the duration of which +we may guess 2,000,000 years, we get, with four years' allowance for +puberty, 500,000 generations. + +7. From Eotetrapoda to a not yet separated or differentiated group +of Crossopterygian and Dipnoan fishes, both of which are known from +Devonian strata. The duration of the latter has been computed at +4,000,000 years, which, with 1,000,000 for the Mountain Limestone +formation, gives us 5,000,000 for this stage. Assuming, for the sake +of round numbers, as much as five years for a generation, we get +1,000,000 generations. + +8. Earliest stage, down to the first fish-like creatures. Teeth and +spines indicating the existence of fishes are known from the Upper +Silurian. By carrying the earliest fishes down to the bottom of the +Silurian, with 2,700,000 years' duration, and allowing three years for +attaining puberty, the calculation results in 900,000 generations. + +Further back we cannot go. We do not know of any Vertebrate remains +from the Ordovician and Cambrian, which together represent 6,700,000 +years, enough for at least half as many generations of Prochordate +creatures. The pre-Cambrian or Laurentian epoch lies quite beyond the +reach of calculation, nor have we any trustworthy fossil remains of +living matter from these strata, to which, however, Haeckel and others +refer the first beginnings of life. + +All the above calculations are, of course, only approximate. What we +do know is the existence of representatives of the stages, our proofs +being the fossils; but when we refer the origin of the Eotetrapoda, +for example, to the bottom and not somewhere to the middle of the +Coal-measures, we are guessing merely. Alterations in the levels +assumed for the various stage-representatives will, of course, alter +the result of the number of generations; but the leading idea, as +a whole, is not thereby upset. The fact remains that in the Upper +Silurian we have fishes; from the Coal-measures onwards, fishes and +Amphibia; since the Permian, fishes, Amphibia, and reptiles; since the +end of the Trias these three classes and the Mammalia; and lastly, at +least since the Plistocene, man himself. If Evolution is true at all, +the transformation from early fish-like creatures to man has come about +within these epochs. Being able to assign a time of duration to each +of them, with an approximate total of 21,000,000 years, we are also +able to put the whole ancestral series to a test by expressing each +great stage in generations. The result is very satisfactory. The whole +enormous stretch from the lowest fish-like creatures to man has been +resolved into more than 5,000,000 successive generations, and each of +these means a little step forwards in onward Evolution. + +Nothing is to be gained for the understanding of our problem of +Evolution if we multiply this enormous number of generations by ten +or any other multiple. We are not able to conceive changes so small +as those which necessarily have existed between Pithecanthropus and +man if the whole striking difference is analysed into 17,000 steps. +Every one of these stages in the modifications of the muscles, the +skeletal framework, increase of brain, shortening of the trunk, +lengthening of the legs, improvement of the hands, loss of the hairy +coat, etc., is truly microscopical, imperceptible, just as the +Evolutionist imagines the whole process to have been. Again, where is +the difficulty implied by the change from an air-breathing, in many +structural points half-amphibian, fish into a primitive land-crawling +four-footed creature, if we are allowed to resolve the transformation +into 1,000,000 stages? So far from there being any difficulty, rather +does it appear questionable if so many infinitely small changes have +been necessary to bring about this result. + +One thousand years make apparently no difference in the evolution of +animals, nor does one second change the aspect of the hands on the +face of a clock, nor did Julius Caesar's commission of scientific men +appreciate the error of about eleven minutes in the length of the year +beyond its real value; but now the Russians are, owing to this neglect, +nearly two weeks behind the civilized nations. + + + THE END. + + + BILLING AND SONS, PRINTERS, GUILDFORD. + + + By PROFESSOR ERNST HAECKEL + + + MONISM; + OR, + The Confession of Faith of a Man of Science. + + Translated from the German by J. D. F. GILCHRIST. + + _Crown 8vo., cloth. Price 1s. 6d. net._ + +'We may readily admit that Professor Haeckel has stated his case with +the clearness and courage which we should expect of him, and that +his lecture may be regarded as a fair and authoritative statement +of the views now held by a large number of scientifically educated +people.'--_Times._ + +'The Monism, which is the substance of his faith, is thus defined by +him: "Our conviction that there lives one spirit in all things, and +that the whole cognizable world is constituted, and has been developed, +in accordance with one common fundamental law." As the confession +of a distinguished man of science, this little work deserves to be +read.'--_North British Daily Mail._ + +'This "Confession of Faith" was delivered by the great German +scientist, its author, as an extemporaneous address at Altenburg +rather more than two years ago. There are, no doubt, a large number of +English readers who will welcome a translation, for this "connecting of +religion and science" has long troubled many earnest students of modern +science.'--_Publisher's Circular._ + +'This is a little book of great daring, an example of the wild +speculative flights of one of the very ablest and greatest of our +contemporary men of science.'--_Aberdeen Free Press._ + +'The address, whatever we may think of its conclusions, is, however, +most interesting reading, and is admirably done into English by the +translator.'--_Literary World._ + + + LONDON: ADAM & CHARLES BLACK, SOHO SQUARE. + + + _Demy 8vo., price 7s. 6d. net._ + + SOURCES OF THE APOSTOLIC + CANONS. + + _With a Treatise on the Origin of the Readership and other Lower Orders._ + + By Professor ADOLF HARNACK. + + Translated by LEONARD A. WHEATLEY. + + _With an Introductory Essay on the Organization of the Early Church + and the Evolution of the Reader._ + + By the Rev. JOHN OWEN, Author of 'Evenings with the Skeptics.' + +'Dr. Adolf Harnack is at the present time undoubtedly the leading +liberal authority in Germany on matters connected with early Christian +history.'--_The Times._ + +'Those who are interested in early Church history know how to prize +anything from the pen of Prof. Harnack. They will not be disappointed +with the present paper, in which, with his accustomed learning and +acute criticism, he annotates and comments upon the fragments of +primitive church law which partly form the basis of the Apostolic +Canons.'--_British Weekly._ + +'The wide circulation of this volume would be of the happiest augury +for a more scientific and worthy conception of the organization of the +primitive Church.'--Dr. MARCUS DODS in _The Bookman_. + + + + _Crown 8vo., cloth, price 1s. 6d. net._ + + CHRISTIANITY AND HISTORY. + + By ADOLF HARNACK. + + Translated, with the Author's sanction, by THOMAS BAILEY + SAUNDERS, with an Introductory Note. + +'It is highly interesting and full of thought. The short introductory +note with which Mr. Saunders prefaces it is valuable for its +information and excellent in its tone.'--_Athenaeum._ + +'A singularly able exposition and defence of Christianity, as seen in +the newer light, by one of the most learned and acute "evangelical" +critics of Germany. The essay is a masterly one.'--_Glasgow Herald._ + +' ... We hope the lecture will be widely read.'--_Primitive Methodist +Quarterly Review._ + +'The lecture itself is weighty in its every word, and should be read +and re-read by those desiring to have in a nutshell the central +positions of modern Christianity.'--_Christian World._ + + + LONDON: ADAM & CHARLES BLACK, SOHO SQUARE. + + + _Third Edition. Crown 8vo., cloth, price 5s._ + + SKETCH OF THE HISTORY OF + ISRAEL AND JUDAH. + + By J. WELLHAUSEN, + PROFESSOR AT MARBURG. + +'This work is now issued for the third time as an independent treatise. +It admirably epitomizes the subject, and exhibits on almost every page +evidences of Professor Wellhausen's profound study.'--_Publishers' +Circular._ + +'We would only say that those who differ from his critical views will +yet do well to study them, and to read this history in which he applies +them. Its separate publication, in a handy form and at a moderate +price, makes it generally accessible.'--_North British Daily Mail._ + +'The publication in a separate form of Professor Wellhausen's article +in the "Encyclopaedia Britannica" on "Israel" will be very warmly +welcomed by many readers.'--_Manchester Guardian._ + +'We are very glad to welcome an edition of Professor Wellhausen's +"Sketch of the History of Israel and Judah" in a convenient and handy +form. This is the first time it has appeared in a separate form. It is +already known to students; it ought now to become popular. It is based +on the learned author's studies in Hebrew literature and history, and, +though not controversial in form, it differs totally from orthodox +presentations of the subject.'--_Westminster Review._ + +'A sketch which has created such widespread and profound interest as +this could not be kept in the pages of a voluminous encyclopaedia. +Wellhausen's words necessarily have exceptional importance, even in +the esteem of those who differ from him _toto coelo_.'--_Baptist +Magazine._ + +'The profound scholarship of the author does not elevate his writing +above the interest of the general reader, and a vivid idea of the +involved Jewish history is obtainable from this volume.'--_Christian +Advocate._ + + + LONDON: ADAM & CHARLES BLACK, SOHO SQUARE. + + + _Demy 8vo., boards, price 3s. 6d. net._ + + A CLASSIFICATION OF + VERTEBRATA, + RECENT AND EXTINCT. + + With Diagnoses and Definitions, a Chapter on Geographical + Distribution, and an Etymological Index. + + By HANS GADOW, M.A., PH.D., F.R.S., + + STRICKLAND CURATOR AND LECTURER ON ZOOLOGY TO THE UNIVERSITY, + CAMBRIDGE. + +'At the end of his work Dr. Gadow adds a useful chapter on the +geographical distribution of the Vertebrata, with a table showing +the approximate number of the known recent species. He also gives +a fanciful though striking calculation to show how some groups are +still in the ascendant, while others are distinctly declining. The +little volume is indeed a welcome addition to the biological student's +library, and it deserves the wide circulation which its author's +eminence is likely to ensure for it.'--_Natural Science._ + +'It is a book, it need hardly be said, for the student; it is simply +a list of the principal sub-divisions of backboned animals, with just +as much definition as is needed. It may be regarded as an exceedingly +concentrated extract of a full text-book of the vertebrates.'--_Daily +Chronicle._ + + + + _Demy 8vo., cloth, price 21s._ + + IN NORTHERN SPAIN. + + By Dr. HANS GADOW, M.A., PH.D., F.R.S. + + _Containing Map and 89 Illustrations._ + +'Some years back "Wild Spain," one of the best books of its kind, +made you desirous of knowing more of the country. And Hans Gadow has +deepened this feeling in his excellent volume "In Northern Spain," +and that to an enormous extent. Dwelling at inn or farm, or in their +own tent, they saw the country as it has been seen but rarely, and +they came to know the inhabitants as they can be known in no other +fashion.'--_Black and White._ + +'To persons visiting the provinces with which the author deals, this +book will be invaluable, and will do more to point their attention to +objects of interest than existing guide-books of Spain, most of which +are out of date.'--_The Field._ + +'About the best book of European travel that has appeared these many +years.'--_Literary World._ + + + LONDON: ADAM & CHARLES BLACK, SOHO SQUARE. + + +Transcriber's Notes + + Variations in spelling, punctuation and hyphenation have been retained + except in obvious cases of typographical errors. + Inconsistent hyphenation and spelling are as in the oringinal. + Italics are shown thus _italic_ and underline thus *underline*. + + + + + +End of the Project Gutenberg EBook of The Last Link, by Ernst Haeckel + +*** END OF THIS PROJECT GUTENBERG EBOOK THE LAST LINK *** + +***** This file should be named 44541.txt or 44541.zip ***** +This and all associated files of various formats will be found in: + http://www.gutenberg.org/4/4/5/4/44541/ + +Produced by Chris Curnow, Les Galloway and the Online +Distributed Proofreading Team at http://www.pgdp.net (This +file was produced from images generously made available +by The Internet Archive) + + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. 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