Percy E.Davidson Recapitulation Theory and Human Infancy THE RECAPITULATION THEORY AND HUMAN INFANCY BT PERCY E. DAVIDSON, PH.D. ATE PROFESSOR OF EDUCATION, LELAXD STANFORD JUNIOR UNIVERSITY TEACHERS COLLEGE, COLUMBIA UNIVERSITY CONTRIBUTIONS TO EDUCATION, NO. 65 PUBLISHED BT Utatbers tCnllrgr. Cnlnmbia Smnrrstly NEW YORK CITY 1914 THE RECAPITULATION THEORY AND HUMAN INFANCY BY PERCY E. DA\TDSON, PH.D. ASSOCIATE PBOFES8OB OF EDUCATION, LELAXD STANFORD JUXIOB UNIVERSITY TEACHERS COLLEGE, COLUMBIA UNI\7ERSITY CONTRIBUTIONS TO EDUCATION, NO. 65 PUBLISHED BY ararhrrs Cnllrg?. (Cnlnmhia UniurrHity NEW YORK CITY 1914 Copyright, 1914, BY PERCY E. DAVIDSON ACKNOWLEDGMENTS This paper was presented to the Division of Philosophy of Columbia University as a doctoral dissertation. It was written under the direction of Professor John Angus MacVannel, of Teachers College, to whom is made grateful acknowledgment of kind encouragement and valued suggestions. The writer welcomes the opportunity of expressing his sense of an indebt- edness of a fundamental character to the teachings and gen- erosity of Professor John Dewey. Thanks are due also to Professor J. Perrin Smith, of the Department of Geology in Stanford Unversity, for his courtesy in reading the manuscript. P. E. D. 111 CONTENTS CHAPTER I PAGB INTRODUCTION 1 CHAPTER II THE RECAPITULATION THEORY IN BIOLOGY: A SKETCH OP ITS HISTORY SEC. 1. Other Names for the Theory 5 " 2. Anticipations of the Recapitulation Idea 5 " 3. The "Theory of Types" 7 " 4. Von Baer's Law: The Law of Embryonic Resemblance 8 " 5. The Correspondence Stated as Between Developmental Stages of Existing Animals and the Succession of Adult Forms of Extinct Representatives. Agassiz 9 " 6. Embryology and Darwinism 11 " 7. Darwin 11 " 8. The Developmental-ancestral Correspondence Clearly Enunci- ated: Fritz Muller 14 " 9. " Ontogeny is a Short and Rapid Recapit ulation of Phylogeny" : Haeckel 14 " 10. Herbert Spencer 20 " 11. The Laws of Acceleration and Retardation 23 " 12. The Facts of Recapitulation 28 a. Those of Palaeontology 29 b. Those of Embryonic Resemblance 33 c. Those of Comparative Morphology 37 " 13. Recapitulation and the Physiology of Development 41 " 14. Biological Opinion Regarding Recapitulation 49 " 15. Review and Summary 57 CHAPTER HI HUMAN INFANCY AND RECAPITULATION SEC. 1. Human Embryogeny 62 " 2. The Theory of Infancy 64 " 3. Recapitulation and Human Infancy 77 " 4. Cultural Recapitulation 93 CHAPTER IV CONCLUSION 99 THE RECAPITULATION THEORY AND HUMAN INFANCY CHAPTER I INTRODUCTION The strong interest in its biological and anthropological set- ting which attended the beginnings of the systematic study of childhood in this country has somewhat abated. Among other things practical considerations have drawn attention away to urgent matters of institutional management, while newer and more exact methods, borrowed from the nearby sciences, have been enthusiastically resorted to in the hope of a more immediately serviceable knowledge of childhood than any search into its history could reasonably be expected to yield. Doubtless this change of emphasis is a wholesome one. Ed- ucation has still to find its most advantageous methods, if indeed it has not yet to delimit its field. It is only right, then, that all the methods which have done excellent work in the sciences should be tested and evaluated for their usefulness in its service. It would be a mistake, however, to regard this departure from biology and anthropology as a final one, and to conclude that education has nothing to learn from these sources. Man's animal heritage is too intimate a part of him, and his historical career too significant of his make-up, ever to justify a neglect of these things on the part of those who propose to mould his present condition and in some measure to direct his future. It may be, too, that some sense of disappointment has figured in this willingness of students of childhood to turn in new directions. Fruitful as it was in suggestion, the older genetic line of approach could not, in the nature of the case, lead to 1 2 The Recapitulation Theory and Human Infancy a scientific basis for a practical educational program. This could come only with the aid of an exact and faithful inter- pretation of childhood as it exists in modern societies. Ed- ucational schemes based upon historical inferences were there- fore necessarily precarious and could easily be found unsound when fairly tested. More especially has the older genetic method of study suffered from the discredit into which some of its guiding principles have fallen. One of these principles was embodied in the theory of recapitulation, the idea that the child in its development rehearses the history of its ancestry, and that in consequence its nature may be inferred from the probable course of human evolution. Taken bodily from em- bryology, this idea was projected upon the field of mental gen- esis, where it became a commonplace. More recently dis- quieting rumors from the source of its origin have been heard to the effect that the principle was formulated without suffi- cient warrant, and that it cannot be depended upon even as a helpful hypothesis. Its prestige has in consequence been ser- iously damaged and there is plainly evident great uncertainty as to the degree of truth it may contain. This uncertainty with regard to a principle with important implications for the theory of infancy and psychogenesis, is hardly excusable or necessary. For recourse to the science from which the principle was derived is open, and no obvious reason exists why its real standing there should not be known. If education is to be spared the humiliation which comes in- evitably from building on the sand, it must earnestly endeavor solidly to ground its doctrine. Especially is this true when this doctrine is drawn from the pure sciences, for a thorough knowledge of these on the part of outsiders is not easy of attain- ment and a little knowledge is a dangerous thing. Moreover, the position of education is peculiarly difficult, for as an art its practice is not only dependent upon science as such; more than one science is implicated. Education is none the less in duty bound either to acquaint itself with the true value of these borrowed principles or to leave them alone. This paper represents an effort to discover something of the status of recapitulation in biology and to note its implications for the period of infancy. It makes no pretensions to scholarly exhaustiveness. Its justification is the lack of any accessible Introduction 3 account of the history and present position of the idea to which students of psychogenesis may refer, and its one merit is that it stands for a conscientious attempt to understand and report some of the more obvious aspects of the discussion. At some future time someone with the requisite knowledge of biology, anthropology, and psychology will do full justice to the topic and supply us with an authoritative account of the matter. Meanwhile we can at least clear away the superficial obstacles and prepare ourselves for the more complete statement. No one can justly object to a desire on the part of students of childhood to know its biological history and its nature in con- sequence. It is at least a legitimate object of curiosity. More than this, no situation ever failed to become more intelligible, and so more amenable, in the perspective yielded by its history. On the side of possible cultural homologies in infancy and child- hood there is the chance of a more direct usefulness. Some years ago Professor Dewey inquired pointedly as to what good could come from a knowledge of the historical genetic order, when an argument from it directly to the proper treatment of growth is not warranted. And it must be admitted that there are positive limits to the use of principles derived from this source. Education must be based primarily upon a knowledge of the ontogenetic order itself. But it appears already that the ontogenetic order is not easy of discovery. Although childish and youthful performances can be objectively described and in many cases measured, the true inward significance of these performances is determined with the greatest diffi- culty, because it is ultimately a matter of interpretation. Is it not possible, then, that a knowledge of historical processes may have something to offer, not as principles upon which ac- tion shall be based, but as cues and hypotheses with which to approach the exceedingly intricate phenomena of individual psychogenesis? Historical processes expressed themselves slow- ly. They were made with difficulty and became registered step by step in objective products which lie open the world over for sympathetic inspection. If a warrant can be found in general terms for some degree of correspondence between in- dividual psychogenesis and social or historical development, it seems not impossible that a close study of the latter order may yield suggestions of real value with which to approach 4 The Recapitulation Theory and Human Infancy the difficulties of the first. At least the possibility should not be denied in advance of a fair trial. Obviously the resources of child psychology would be immensely amplified if they might include those of comparative psychology and ethnology. This hope may stand as some justification for the present effort to clear away some part of the obscurity which gathers about the relations of the child and the race. If this should be in- sufficient there still remains the interest which attaches to a knowledge of the net result of one phase of a significant pioneer movement in the study of childhood. THE RECAPITULATION THEORY IN BIOLOGY: A SKETCH OF ITS HISTORY 1. Other Names for the Theory. "This has been named by Hatschek the 'morphogenetic theory,' by Hyatt the 'law of morphogenesis,' by Haeckel the 'biogenetic law,' by Cope the 'doctrine of parallelism,' and by Morgan the 'repetition theory.' Sometimes it has been alluded to as the 'law of von Baer,' but incorrectly, for von Baer was its severest critic." * 2. Anticipations of the Recapitulation Idea. The idea that embryos of higher forms pass through the adult stages of the lower animals is a very old one and no one name is associated with its origin. The first clear reference to it appeared at the end of the eighteenth and the beginning of the nineteenth centuries. The system of classification then in vogue was that of Linnaeus, which placed the various groups one above the other in a single scale or series from the lowest to the highest. .In this scale the worms held the lowest rank, and then in order, the insects, fishes, amphibia, birds, mammals. The allusions to the animal series in the extracts which follow are therefore to this uniserial system. In these early expressions embryonic or developmental stages were naturally found to resemble the mature forms of existing lower animals, evolution as yet being a conception of a very few prophetic minds. One of the earliest of these expressions, however, was that of such a prophetic mind. Lor- enzo Oken, a speculative evolutionist and a popularizer of the science of the time, wrote in 1805, "Each animal 'metamorphoses itself through all animal forms. The frog appears first under the form of a mollusk in order to pass from this stage to a higher one. The tadpole 1 Montgomery. Analysis of Racial Descent in Animals, 1906, p. 177. 5 6 The Recapitulation Theory and Human Infancy stage is a true snail; it has gills which hang free at the sides of the body as is the case in Unio pictorum. It has even a byssus, as in Mytilus, in order to cling to the grass. The tail is nothing else than the foot of the snail. The metamorphosis of an insect is a repetition of the whole class, scolopendra, oniscus, julus, spider, crab."2 Later, in 1883, Oken wrote, in reference to the same matter, "There is no doubt that we have here a striking resemblance, and one that justifies us hi thinking that the development in the ovum is merely a repetition of the story of the creation of the animal groups."3 Here, plainly enough, is a statement in crude form of the idea of recapitulation which was to have clear definition with the advent of the doctrine of descent, and which was destined to play so important a role in the history of that doctrine. The other early references to be noted make comparisons of development with the rank of existing animals. Thus, Wal- ther, in 1808, said, "The human foetus passes through its metamorphosis in the cavity of the uterus in such a way that it repeats all classes of animals, but, remaining permanently in none, develops more and more into the innate human form. First the embryo has the form of a worm. It reaches the insect stage just before its metamorphosis. The origin of the liver, the appearance of the different secretions, etc., show clearly an advance from the class of the worm into that of the mollusk."4 The embryologist Meckel, in 1808, 1811, and 1821, gave greater definiteness to these comparisons: "He held that the embryo of higher forms, before reaching its complete development, passes through many stages that correspond to those at which the lower animals appeared to be checked through their whole life. In fact the embryos of higher animals, the mammals, and especially man, correspond in the form of their organs, in their number, position, and proportionate size, to those of the animals standing below them. The skin is at first, and for a considerable period of embryonic life, soft, smooth, hairless, as in the zoophytes, medusae, many worms, mollusks, fishes, and even in the lower amphibians."6 ' Quoted by Morgan, Evolution and Adaptation, 1903, p. 59. » Quoted by Bolsche, Haeckel, His Life and Works, translated by J. McCabe, p. 227. • Quoted by Morgan, loc. cit., p. 59. •ZWd. The Recapitulation Theory in Biology 7 Many other instances were given by Meckel, some fantastic and absurd, others still to be found in the text-books on em- bryology. It was this conception that met with the opposition of von Baer, writing in 1828. Von Baer refers to "The accepted idea, that the embryo in higher animals passes through the permanent forms of the lower. . . . This idea, which was born in a time when, besides Malpighi and Wolff, no connected investigations had been undertaken upon the early periods of the embryology of any animal, and was especi- ally carried out by a man who possessed perhaps the most knowledge upon the embryology of the higher organisms, could not help but arouse great support, because it was based upon a multitude of special proofs. . . . Some supporters were so zealous that they spoke no longer of similarity, but of complete identity, and acted as though the correspondence were proven universally and in each particular. We read a short time ago, in a paper upon the blood circulation of the embryo, that the human embryo does not omit a single animal form."6 "That," remarks Montgomery, "must indeed have been the luscious Springtime of the theory!" Von Baer urged against the prevailing view of recapitulation " (1) that no adult animal ever has a yolk sac, or (2) is sur- rounded by embryonic fluids; (3) that it is not the case that an embryo of a higher animal in each embryonic stage corresponds in every point with an adult of a lower species, or (4) that in the ontogeny of a lower form structural relations do not occur which are found in the adult of a higher; (5) that it is equally not the case that parts which are characteristic of only the high- est forms appear latest in the ontogeny."7 S. The ''Theory of Types." Recapitulation in its next phase became intimately involved in that scientific theory of the natural world which preceded the evolutionary or Darwinian conception now current, and which stubbornly contested the claims of the latter until over- whelmed by an incontrovertible array of fact. It is known as the "theory of types," and is associated especially with the names of Georges Cuvier, Louis Agassiz, Johannes Mueller, and Richard Owen. The conception has been analyzed and traced to various sources by Merz in his "History of European • Quoted by Montgomery, Joe. cit., p. 177. ' Ibid, p. 176. 8 The Recapitulation Theory and Human Infancy Thought in the Nineteenth Century."8 Only its more general character need be noted here. It was, in brief, the logical culmi- nation of the progress of descriptive science following the Re- vival of Learning. From independent beginnings, embryology and physiology, comparative anatomy, geology and geography, and botany, had by degrees and in unrelated ways accumulated a vast amount of unorganized knowledge which by the first quarter of the nineteenth century invited a general and unified formulation. The outcome was a conception constituted in part of inductions and analogies derived from the observation of nature, in part of the literal biblical interpretation of the overshadowing Puritanism of the time.9 In this theory the plan of arranging the animal groups in a single scale or series gave way to a system in which the species were regarded as modifications of four main "types" or "em- branchements," independent and equivalent "plans of struc- ture," namely, the vertebrate, articulate, radiate, and mol- luscan. The species representing these great types were "fixed," in the sense that they had been separately created as they were found to be, and were in no wise genetically related. The study of fossils and geological formations led to the addi- tional idea that species had suffered extinction coincident with colossal revolutions or catastrophes in the life of the planet, succeeded by the creation of new types. Only by the intervention of such episodes could be explained the succession of life forms so unequivocally indicated in these phenomena. 4- Von Baer's Law: " The Law of Embryonic Resemblance." Von Baer was identified with the theory of types; in fact he seems to have had some share in its formulation, although he did not go to the extremes of its chief exponents. His views of the significance of embryonic development are therefore to be understood with this theory as a background. For von Baer did not merely criticize the prevailing ideas of Meckel and others on this subject. A distinguished embryologist, he held original and striking ideas of his own, which had a large place in the subsequent history of the discussion. Von Baer's position is represented by the following laws, which he formulated: •Vol. II, Chap. IX. » Poulton, Essays on Evolution, pp. 56, 57. The Recapitulation Theory in Biology 9 " (1) That the general of a large animal group expresses itself earlier in the embryo than the special. (2) Out of the most general of the structural relations evolves the less general, and so forth until finally the most special appears. (3) Each em- bryo of a particular animal form instead of passing through the other particular forms, separates itself rather from them. (4) In reality accordingly the embryo of a higher form is never like to another animal form, but only to its embryo."10 Morgan illustrates these laws as follows: "For example two similar species of pigeons will follow the same method of development up to almost the last stage of their formation. The embryos of these two forms will be practically identical until each produces the special characters of its own species. On the other hand two animals belonging to different families of the same phylum will have only the earlier stages in common. Thus, a bird and a mammal will have the first stages similar, or identical, and then diverge, the mammal adding the higher characters of its group. The resemblance is between corresponding embryonic stages and not between the embryo of the mammal and the adult form of a lower group. "Von Baer was also careful to compare embryos of the same phylum with each other, and states explicitly that there are no grounds for comparison between embryos of different groups. . . In one place von Baer raises the question whether the egg may not be a form common to all the phyla. "u The phyla alluded to are, of course, the four great groups or types. It is important to remember that von Baer had reference in his statements to likenesses among existing animals, and not to ancestral relationships. Von Baer did not accept evolution although the issue between the two theories had been well drawn before his death. Later Herbert Spencer pointed out that a thoroughgoing application of von Baer's law in filial and ancestral relationships implied the recapitulation of Oken, that is, the idea that the embryogeny "repeated the story of the creation of the animal groups." 5. The Correspondence Stated as between Developmental Stages of Existing Animals and the Succession of Adult Forms of Extinct Representatives. Agassiz. Von Baer's significant contribution to the discussion did not exert an immediate influence. It was Louis Agassiz, a pupil of Cuvier, the principal originator of the type theory, who made »• Quoted by Montgomery, toe. cit., p. 178. uLoc. cit., p. 61. 10 The Recapitulation Theory and Human Infancy recapitulation an integral element in this theory and gave it its- new form. Early in his life Agassiz entered upon elaborate studies of living and fossil fishes and so came upon resemblances between developmental phases of living animals and the adult forms of their extinct representatives. As his interest broadened to include the systematic classification of the whole animal world, Agassiz relied more and more upon the facts of embry- ology to make good the deficiencies of fossil remains and to pre- vent the confusion, inevitable as he believed, from an examina- tion of anatomical differences alone. In 1857 he wrote, "I satis- fied myself long ago that embryology furnishes the most trust- worthy standard to determine the relative rank among animals." In the system ultimately evolved by Agassiz, descriptive of what he believed to be the natural order, there were four great parallelisms, or systems of relationship. These were (1) a paral- lelism between the geological succession of animals and their relative standing or structural gradation; (2) a parallelism be- tween the geological succession of animals and the individual development of their living representatives; (3) a parallelism between the relative rank or gradation of animals and their individual development; and (4) these several series were again related to geographical distribution. Thus "the phenomena of animal life correspond to one another, whether we compare their rank as determined by structural complication with the phases of their growth, or with their suc- cession in past geological ages; whether we compare this succes- sion with their embryonic growth, or all these different relations with each other and with the geographical distribution of ani- mals upon earth. The same series everywhere!"12 This interlocking system of relationship constituted the ground- work of the "plan of creation" Agassiz's "Essay on Classifica- tion" was meant to delineate, a plan very satisfying to his own religious sentiments, if indeed it was not inspired by them. "Shall we," he exclaims, "by any false argumentation, allow ourselves to deny the intervention of a Supreme Intellect in calling into existence combinations in nature by the side of which all human conceptions are child's play?"13 "Essay on Classification, 1857, p. 196. "Ibid., p. 197. The Recapitulation Theory in Biology 11 It was the second parallelism, that between the succession in geological time and the embryonic stages of living representa- tives, that constituted the new phase in the history of recapitula- tion. Of this he said more particularly, "These relations, now they are satisfactorily known, may also be considered as exemplifying, as it were, hi the diversity of animals of an earlier period, the pattern upon which the phases of the development of other animals of a later period were to be established. They appear now, like a prophecy in those earlier times, of an order of things not possible with the earlier combina- tions then prevailing in the animal kingdom, but exhibiting in a later period, in a striking manner, the antecedent considerations of every step in the gradation of animals."14 There is here suggested Agassiz's well known concept of "prophetic types," the facts for which, as well as for his "syn- thetic" and "progressive" types, were so significant to other minds of a genetic relationship he himself refused to acknowledge. 6. Embryology and Darwinism. This correspondence between embryonic stages and the geo- logical succession of animal forms was destined to play an im- portant part with the advent of Darwinism (" Origin of Species," 1859). It will be well to indicate at once the three allied uses toy which the facts of embryology were put in the development of this theory. They became, in the first place, one main sup- port to the doctrine of descent itself. This was naturally the value attached to them chiefly by Darwin. Once the doctrine was accepted, embryology was employed with all degrees of assurance to determine the affinities of living animals in the interests of a classification based upon genetic relationship. Fritz Miiller was one of the first of a long line of students to demonstrate their usefulness from this viewpoint. Finally, as this classification became elaborated, it made possible the trac- ing back of genealogies, phytogenies, or racial histories, and this was introduced systematically by Haeckel. 7. Darwin. By the time of the sixth edition of the "Origin of Species" in 1872, the two applications of the facts of embryology just men- tioned had been made and had received the sympathetic notice Essay on Classification, 1857. p. 155. 12 The Recapitulation Theory and Human Infancy of Darwin. The contribution of Fritz M tiller to the classifica- tion of the Crustacea, largely by the aid of embryology, had been of particular interest to him, and Haeckel's work with phylogenies was alluded to with approval.16 Darwin's treatment of the facts under discussion is found in Chapter XIV of the sixth edition where he deals with the mutual affinities of organic beings. Referring to the efforts of the "special creationists" to arrange a "natural system" in ac- cordance with the divine plan, he urges that such a plan is mean- ingless unless it relates to time and place and has a specific con- tent, and that all the rules, aids, and difficulties in the then current efforts at classification are well explained by a view of a natural system founded on descent with modification. In support of this contention he proceeds to submit to scrutiny the several kinds of recognized affinities among animals, those of embryology among them. After a citation of facts, including some of von Baer and a direct reference to his law of embryonic resemblance, Darwin asks, "How then can we explain these several facts in embryology, — namely, the very general, though not universal, difference in structure between the embryo and the adult; — the various parts in the same individual embryo, which ultimately become very unlike and serve for diverse purposes, being at an early period of growth alike; — the common, but not invariable, resemblance between the embryos or larvae of the most distinct species in the same class; — the embryo often retaining whilst within the egg or womb, structures which are of no service to it, either at that or at a later period of life; on the other hand larvae, which have to provide for their own wants, being perfectly adapted to the surrounding conditions; — and lastly the fact of certain larvae standing higher in the scale of organization than the mature animal into which they are developed?" The explanation is contained in the two principles, viz., " . . . that slight variations generally appear at a not very early period of life and are inherited at a corresponding not early period." Darwin's illustration helps to make his meaning plain, "Now let us apply these two principles to species in a state of nature. Let us take a group of birds, descended from some ancient form and modified through natural selection for differ- "Origin of Species, American ed., p. 231. The Recapitulation Theory in Biology 13 ent habits. Then, from the many slight successive variations having supervened in the several species at a not early age, and having been inherited at a corresponding age, the young will have been but little modified, and they will still resemble each other much more closely than do the adults, — just as we have seen with the breeds of pigeons."16 For Darwin did not fail to verify his statements by carefully measuring young and old dogs, horses, and pigeons. Accord- ingly, "It is highly probable that with many animals the embryonic or larval stages show us, more or less completely, the condition, of the progenitor of the whole group in its adult state." Furthermore, "we can see why ancient and extinct forms so often resemble in their adult state the embryos of existing species of the same class. Agassiz believes this to be a universal law of nature; and we may hope hereafter to see the law proved true. It can, however, be proved true only in those cases in which the ancient state of the progenitor of the group has not been wholly obliterated, either by successive variations having super- vened at a very early period of growth, or by such variations having been inherited at an earlier stage than that at which they first appeared. It should also be borne in mind that the law may be true, but yet, owing to the geological record not extending far enough back in time, may remain for a long period, or forever, incapable of demonstration. The law will not strictly hold good in those cases in which an ancient form became adapted in its larval state to some special line of life, and transmitted the same larval state to a whole group of descendants; for such larvae will not resemble any still more ancient form in its adult state."17 These passages have a peculiar interest in the light of the later history of the discussion. There is every intention evident of doing full justice to the complexity of the facts and a plain acknowledgment of a variety of cases. Nevertheless, one de- tects an unmistakable leaning in the direction of a general state- ment favorable to recapitulation, and in the allusion to Agassiz an expressed sympathy for a "universal law of nature." With the great authority of Darwin offering this much justification, one cannot be surprised if in the hands of less careful students the facts should be found to warrant a much more sweeping statement. >• Origion of Species, American ed., pp. 245, 247, 249. "Ibid., pp. 252, 254. 14 The Recapitulation Theory and Human Infancy 8. The Developmental-Ancestral Correspondence Clearly Enunciated: Fritz Mutter. It has been noted that Darwin had profited by the contribu- tion to his theory made by Miiller in his book, "Fur Darwin," published in 1864. Torn between the claims of the rival theories, Miiller determined rigidly to apply the principles of Darwin to one group, the Crustacea, in order to discover whether lines of descent and a genetic classification could in this manner be determined within it. In concluding his study Miiller general- ized upon the facts of resemblance between the developmental history of descendants and the adult state of ancestors in a more precise manner than Darwin had in his first edition. His con- clusions are as follows: "Descendants, therefore, reach a new goal, either by deviat- ing sooner or later whilst still on the way towards the form of their parents, or by passing along this course without deviation, but then, instead of standing still, advance still further. "In the second case the entire development of the progenitors is also passed through by the descendants, and, therefore, so far as the production of a species depends upon this second mode of progress, the historical development of the species will be mir- rored in its developmental history. "The historical record preserved in developmental history is gradually effaced as the development strikes into a constantly straighter course from the egg to the perfect animal, and it is frequently sophisticated by the struggle for existence which the free-living larvae have to undergo. "Which of the different modes of development at present occurring in a class of animals may claim to be that approach- ing most nearly to the original one, is easy to judge from the above statements."18 9. "Ontogeny is a Short and Rapid Recapitulation of Phylogeny:" Haeckel. In the statement of principles quoted above from Fritz Miiller it will be observed that there is no disposition to weight the cases of recapitulation in very great disproportion to those of embry- onic or larval deviation. Two possible courses of development are shown, recapitulation being the second. And there is little disposition, if any, to make the second class of cases the more prevalent or the more characteristic in any fundamental " Facts and Arguments for Darwin, pp. Ill, 112, 114. The Recapitulation Theory in Biology 15 It was noticed, too, that Danvin hesitated to formulate a gen- eralization distinctly in favor of recapitulation, whatever may have been his inclination. It remained for Haeckel to raise M tiller's second class of cases into very great prominence at the expense of the first, to assume that this represents the more general, and indeed in some fashion a necessary order, and to throw together all the cases of the first class as mere subsidiary disturbances of the order represented by the second. Thus the "law of recapitulation" took the form in which it is best known. It is interesting to consider the consequences if by chance the emphasis had been placed the other way round. Then the "law" would have read somewhat as follows: Ontogeny records the adaptations the life history of descendants has made in its evolution and is indicative of its phylogeny in those cases only in which embryonic or larval deviation has not occurred. Haeckel's great popularity as a writer gave his statement very wide currency, in fact, made it dominant. It has happened in consequence that the whole succeeding history of the discus- sion, including its application to mental growth, has turned largely upon either the possible substantiation of his "biogenetic law," or upon its possible refutation. It may be said with justice that much of the mischief that has resulted from a care- less use of his formula has been due to the particular form in which the facts were thus summarized. Haeckel was a young man beginning his career at Jena when Darwin's great book appeared. The circumstances of his train- ing had been such as to prepare his mind for the new doctrine and he became its most ardent advocate and disseminator in Ger- many. Haeckel was not content to limit himself to a study of the causes of descent. At once speculative and intrepid, he carried the doctrine in every direction his system-loving mind pointed, and ultimately built a complete natural philosophy upon it. He would not demonstrate the kinships within one class only, as had Fritz M tiller. Nothing less than a genealogical tree of the entire animal world became his object. Haeckel was particularly interested in the two extremes of descent concerning which Darwin had been less explicit, that of the ancestry com- mon to the great phyla among the lowest forms, and that of man. His original investigations were consequently directed upon the lowest orders and he was able to suggest a succession of 16 The Recapitulation Theory and Human Infancy steps by which the Metazoa had evolved from the simplest form of living matter. This he in turn derived from the inanimate. Haeckel was equally consistent in applying the doctrine of descent to mankind. The groundwork of his entire system was laid in the "Generelle Morphologic, "published in 1866, his numer- ous later publications being practically extensions of this work. In this book Haeckel recurs to the threefold parallelism of Agassiz between the order represented by the classification of existing animals and those of palaeontology and of individual development.19 But in place of the mystic bond of connection between the three of Agassiz, Haeckel substitutes a "close cj(stial nexus' ' derived from the theory of descent in the two factors of heredity and adaptation. This primary conception assists in the understanding of his attitude toward recapitulation, for it is the keynote to his whole system. When one considers the situation in 1866 and the nature of his general purpose, it is not surprising that Haeckel should have reverted to this threefold parallelism. To his mind Darwin had shown conclusively the truth of the doctrine of descent with modification. Obviously the hierarchy of living forms, from the lowest one-cell condition through the several grades of complication to the highest, was a result of descent, and was at least suggestive of what the historical order had been. It would therefore correspond with the actual historical order so far as this was indicated by the succession of fossils in the earth's formations. The gradual progression through development from the ovum to the complicated adult was again suggestive of this order in its broad outlines at least. All three of these had served Darwin as foundations for his theory, and the least plausible, that of development, had received a certain warrant in fact in the writings of Darwin and Fritz M tiller, besides having had a respectable history prior to the descent theory. Development, indeed, presented in the concrete the only avail- able picture of what the idealized evolution of animals through geological time presupposed. This suggestiveness of develop- ment has often been alluded to since Haeckel, and still is, by biological students. If one is content wtih exceedingly broad " " . . . die Stufenleiter des nattirlichen Systems mlt den parallen Stufenleltern. der individuellen und der palaontologischen Entwickelung in dem engsten mechani- schen Causalncxus steht." Gen. Morph. II, XIX. The Recapitulation Theory in Biology 17 outlines one may still hold with justice for the truth of this threefold parallelism.20 Its recurrence with Haeckel was con- sequently the obvious thing on the part of one who desired to present a panoramic view of the natural world after the manner of Humboldt and Agassiz. The imperfections of the parallel- ism would naturally appear subsequent to its original formula- tion. It may have been the prestige of this parallelism in his mind, together with the fact that he was for the time primarily a morphologist, as the title of his book implies, that led Haeckel to over-simplify the effects of heredity and adaptation through- out descent, and to neglect somewhat the question of what was required of these two factors to substantially support the paral- lelism. This had been a matter of primary concern to Darwin and Miiller, as has been noted. Throughout his works the ontogenetic-phylogenetic parallelism is associated especially with the "laws" of hereditary transmission at correspond- ing ages and in corresponding place relations, and with that of abbreviated heredity suggested by Miiller.21 The effect of the first two was to repeat the parental order; the effect of the last was to simplify and shorten this order perhaps, but not to destroy it. This is essentially the situation in the fifth edition of the "Evolution of Man,"" where the symbolic representation of the two series indicates omission of ancestral stages, and some modification of them in ontogeny without obscuring their identity. The appearance of novelty, or variation, was identified by Haeckel with adaptation, or the direct modifying effect of environment. This again would explain in part his over-em- phasis of the conservative influence of heredity, for the ever- recurring changes induced by germinal variations regardless *• " It is indisputable, if we only consider the most general features, that the history of the development of an individual is a kind of rapid recapitulation of the slow phases of the evolution of the species and of the branch." Deperet.Transfonnations of the Animal World, trans. 1909, p. 254. 11 "Der Parallelismus zwischen der phyletischen (palaontologischen) und dei bion- tischen (individuellen) Entwickelung erklart sich einfach mechanisch aus den Verer- bungs-Gesetzen und insbesondere aus den Gesetzen der gleichzeitlichen, der gleichort- lichen und der abgekiirtzen Vererbung. Alle Erscheinungen. welche die individuelle Entwiekelung begleiten, erklaren sich lediglich, soweit sie nicht unmittlebares Resultat der Anpassung an neue Existenz-Bedingungen sind. aus der palaontologischen Entwickelung der Vorfahren des Individuums. " Gen. Morph. II, p. 372. 13 Trans., 1910, p. 4. 18 The Recapitulation Theory and Human Infancy of adaptation would be eliminated at one stroke. Adaptation would effect embryonic and larval structures, as he clearly points oub, but presumably its principal effect would be to extend the ontogeny in a linear way corresponding to a similar linear extension of the phylogeny through geological time. However this may be, one misses in the accounts of Haeckel the detailed consideration of the effects of heredity, variation, and adaptation in the life-histories of succeeding generations, so noticeable in the treatment of Darwin and Miiller. This, perhaps, is what reasonably might have happened from a pre- occupation with the parallelism he presupposed. The upshot of the matter is that Haeckel greatly overestimated the con- serving force of heredity operating through descent. This renders intelligible his concluding formula: "Phylogeny is the mechanical cause of ontogeny," a true statement when the par- ents and immediate ancestors are considered, only true with respect to the remote ancestors in a phylogeny on the assump- tion that the force of heredity has been fairly constant through- out. It would, however, be unfair to Haeckel to rest an inter- pretation of his biogenetic law upon his formal summaries alone. A consideration of the actual use to which the law was put in elaborating phylogenies presents a somewhat different aspect. For instance, in developing the phylogeny of man the argument invariably proceeds from a comparison of embryonic resem- blances to a discovery of the palingenetic, or racially older, fea- tures by an elimination of the cenogenic, or more recent ad- ditions. Once these older features are determined the bio- genetic law is invoked and the ancestral reference made. In the earlier stages the ancestral reference is to hypothetical ancestral adult forms, as from the gastrula to the Gastraea, or from the coelomula to the hypothetical Coelomaea, and a sequence of such forms results, in keeping with recapitulation in the ordinary sense of a chronological series. But in the later and higher stages the ancestral reference is not to specific ancestral adult characters, but to ancestors having an embry- ogeny with similar features. This last may be illustrated "We see," he says, "that man entirely resembles the higher Mammals, and most of all the apes, in embryonic development as well as in anatomic structure. And if we seek to understand The Recapitulation Theory in Biology 19 this ontogenetic agreement, in the light of the biogenetic law, we find that it proves clearly and necessarily the descent of man, from a series of other Mammals, and proximately from the Primates."23 From ontogenetic resemblances a common ancestry is argued. Clearly this is not recapitulation in the strict sense. But Haeckel is applying the biogenetic law as he understands it, wherefore it must be that he means by recapit- ulation in this application only that an ontogeny presents in its racially older features evidence of value regarding its prox- imate or less remote ancestors. Haeckel's formal general- izations and their actual use thus do not appear wholly in agreement, and if the meaning of principles lies more espec- ially in the work they do, it must be admitted that the common opinion of Haeckel's conception requires some modification. It should be noted that the notion of recapitulation conveyed by the practice just referred to brings Haeckel close to the position of some of the most radical critics of his theory. Whatever the case may be in these particulars, the general effect of Haeckel's formal statements of the biogenetic law was to imply a sequence in embryonic development such in gen- eral that it was broadly descriptive of a similar sequence in phylogeny. His qualifications of the law still did not have the force of robbing the principal statement in the formula of first-rate descriptive value. Moreover his language was such as to suggest some fundamental tendency toward or necessity for recapitulation, which might be obstructed partially so as to "falsify" or "confuse" or "distort" this order. All this is declared to be misleading in its implications. Ontogeny is subject to many factors, of which those favoring recapitula- tion are but of equal value, or even much less than equal value, with the rest. And they are no more natural or to be expected or primary than those with which they associate.24 "Evolution of Man, trans., 1910, p. 307. " Compare this statement from Miall: "I diverge from him [Haeckel] when he says that each animal is compelled to discover its parentage in its own development. ... I admit no sort of neces- sity for the recapitulation of the events of the phylogeny in the development of the individual. ... I am on my guard when he talks of laics, for the term is mis- leading, and ascribes to what is a mere genet al statement of observed facts the force of a command. The so-called laws of natuie (a phrase to be avoided) may indeed enable us to predict what will happen in a few cases, but only when the conditions are uniform and simple — a thing which is common in Physics, but very raie in Biol- 20 The Recapitulation Theory and Human Infancy 10. Herbert Spencer. It is interesting to compare with the views of Haeckel the position of another great systematist whose book appeared in the same year with the "Generelle Morphologic." This book is the "Principles of Biology" of Herbert Spencer. Spencer makes his starting point von Baer's law and does not widely depart from it throughout the account of his first edition. He however cautions his reader against accepting the general- ization as exact. The resemblances among related embryos noted by von Baer "are not precise but approximate. Only leading characteristics are the same: not all the details . . . . each kind of organism, though having a general direction of development like that of the others it is for a time traveling with, shows from the first a tendency to leave the general route — a tendency which presently becomes strongly marked." Still as an average truth the generalization may be regarded as be- yond question. But, "the generalization must not be con- founded with an erroneous semblance of it that has obtained considerable currency. An impression has been given by those who have popularized the statements of embryologists, that during development each higher organism passes through stages in which it resembles the adult forms of lower organ- isms. . . This is not the fact." Thus Spencer repudiates recapitulation in the form it was taking with Haeckel.25 In a later chapter where he presents with the others the embryological arguments for evolution, Spencer is occupied in showing that evolution explains not only the resemblances of embryos but the lack of such resemblances as well. This is due to the very unlike life conditions and consequent unlike adaptations made by different groups in their evolution sub- sequent to their departure from the common ancestor, adap- ogy. " Report of the British Association for the Advancement of Science, 1897, p. 682. Compare also the following from Hyatt : "The use of terms indicating that Nature has confused or destioyed its own on to- genetic records of the transmission of characters in certain cases assumes (1) that these are exceptional cases, (2) that caenogenesis is not the normal mode of trans- mission in certain types In which it occuis, (3) that both of these modes of trans- mission are not affected by tachygenesis, all these implications being erroneous. . . . "destruction," "confusion," or "falsification" are subjective terms inap- plicable to the objective character of the phenomena . . . entirely out of place In natural science." Phylogeny of an Acquired Characteristic, p. 401, footnote. »« VoL 1. 1st American ed., 1898. pp. 143, 144. The Recapitulation Theory in Biology 21 tations which are reflected in embryonic changes. As a result, "the embryological parallelism is qualified by irregularities that are mostly small, in many cases considerable, and occas- ionally great."26 The irregularities in the law noted by Spencer may be briefly enumerated: (1) The substitution of organs and the suppression of organs in certain embryos as compared with others, the first illustrated by the succession of changes in the aerating appliances of the mammalian embryo, the second by the suppression of the foetal teeth of whales; (2) retrograde development, as in the loss of limbs and senses in adult par- asites; (3) substituted modes of development, the two typical modes being direct and indirect. In the former case the development of the animal proceeds from the egg to the adult condition without intermediate stages. In the latter a cir- cuitous route is to be noted involving often many metamor- phoses. The latter mode is that of the higher or more com- plicated animals because it reflects the many changes incident 'to the embryo from the long succession of unlike conditions through which the group has passed. The direct mode is there- fore the substituted mode among the higher animals, the cause being a prolonged constancy of conditions inducing finally an adjustment of all parts of the animal to the settled condition of its life as a wholeX' Similar facts are to be noted among particular organs as such. Subsequent to the publication of the first edition of the "Principles of Biology" Spencer's views suffered a change of emphasis. In later editions the condemnatory sentences re- garding recapitulation are missing. He has found, in fact, that von Baer's law, when carried out consistently in evolu- tionary terms, implies recapitulation.27 "This conception," says Spencer, "of a tree, symbolizing the relationships of types and a species derived from the same root, has a concomitant conception. The implication is that each organism, setting out from the simple nucleated cell, must in the course of its development follow the line of the trunk, some main branch, some sub-branch, some sub-sub-branch, etc., of this embryological tree; and so on till it reaches the ultimate «• Vol. 1, 1st American ed.. 1898, p. 368. 17 See the first two laws of von Baer. p. 9. 22 The Recapitulation Theory and Human Infancy twig representing the species of which it is a member. It must in a general way go through the particular line of forms which preceded it in all past times: there must be what has been aptly called a "recapitulation" of the successive ancestral structures. This, at least, is the conclusion necessitated by the generaliza- tion we are considering under its original crude form."28 Thus in any unfolding embryo there are two sets of energies at work, one tending toward the type of the primitive ances- tors, the other toward the evolved terminal type, the inter- mediate structures being influenced by their conflict. Still other factors intervene to affect the character of development. > One is economy. A premium is placed upon any animal in a series which can mature at a saving in vital energy. This tends to shorten the process. Economy again explains the entire disappearance of intermediate forms in some cases. Economy explains, once more, "preadaptation," in the earlier preparation of structures and functions of increasing size and importance in the life of the evolving animal. A demand for more time in the upbuilding of increasingly complicated organs may also bring about preadaptations. Finally the lack of uniformity in the decrease and disappearance of organs may be explained in several ways: large organs will suffer more than small ones from the principle of economy; decrease in unused organs may not coincide with the evolution of more important ones; ances- tral features may become embodied as parts of new organs; and some disused organs may entail evil by being in the way of the modes of living.29 Spencer's views are inte%e?ting in that while they arrive at an acceptance of the chronological idea of recapitulation, they do so by inferences directly from the law of von Baer. But recapitulation is true only to the extent that von Baer's law holds, and Spencer is very well aware of the variations from the law. His statements thijjl escape the extreme form given to those of Haeckel by the ^jitter's presupposition of a biogenetic fundamental law. Spencp's position is representative of an acceptance of recapitulation more just to the complexities of the facts, and more neaMV in accord with the views of Darwin and M tiller. »Loc. cit., p. 453. • "Ibid., p. 458, «i seq. The Recapitulation Theory in Biology 23 11. The Laws of Acceleration and Retardation. A notable series of investigations in which recapitulation figured largely was inaugurated by Alpheus Hyatt in Boston in the year 1866. Hyatt's original study was made upon fossil shells of certain mollusks, but his method has been used by his pupils and followers with various groups of mollusks and other invertebrates, and even with the vertebrates. This school of investigators has derived so much assistance from recapitulation that they are now to be regarded as its chief defenders. In- deed, one member of the school has declared that "If the em- bryologists had not forestalled them, the paleontologists would have had to invent the theory." "This," observes Cumings, "may be considered as a fair sample of the general attitude of paleontologists of the Hyatt school. . ."w It was suggested by Hyatt that the conditions for making comparisons between development and the "phylocycle" by means of fossil shells are exceptionally favorable. The shell and its parts are highly significant of the structure of the animal, and display in a unique way the important phases of its growth from the later embryonic stages to old age. ^ Moreover, the procession through geological time is abundantly shown in the successive geological formations not only for the adult forms but for the corresponding immature stages in every youthful phase as well.31 It is therefore possible for students of these shells to compare immature stages directly with their own adult condition and with the immature and adult conditions of their predecessors and descendants. These favorable circumstances make the conclusions of this group of investigators of peculiar value within the limits of their field of study. In making these comparisons Hyatt found certain relations prevailing between the development of the individual and the ancestral series, and summarized them by means of a restate- ment of recapitulation, along with an induction original with him, since known as the law of acceleration. . His own words for these two generalizations are: 10 For a valuable summaiy of the work of this school, with bibliographies, see an article by this writer. Paleontology and the Recapitulation Theory, in Proceedings of the Indiana Academy of Sciences, 1908-09 : pp. 305-34O. 11 Phylogeny of an Acquired Characteristic. Proceedings American Philosophical Society. 1893: p. 350. 24 The Recapitulation Theory and Human Infancy "We have endeavored to demonstrate that a natural classifi- cation can be made by means of a system of analysis in which the individual is the unit of comparison, because its life in all its phases, morphological and physiological, embryo, larva, ado- lescent, adult, and old (ontogeny), correlates with the morpholog- ical and physiological history of the group to which it belongs (phylogeny). "All modifications and variations in progressive series tend to appear first in the adolescent stages of growth, and then to be inherited in successive descendants at earlier and earlier stages according to the law of acceleration, until they either become embryonic or are crowded out of the organization and replaced in the development by characteristics of later origin."32 The term acceleration is not to be understood as implying neces- sarily a quicker development. On the contrary, "an animal having accelerated development of characteristics does not necessarily have a quick development, but may grow, so far as time is concerned, even more slowly than others of its own group."33 The accelerated characteristic merely takes a new relative position in the whole ontogeny by reason of the omis- sion or suppression of the earliest or older stages and the addition of adaptive phases at the adult end. The evolutionary explanation of the law is as follows: "We can fully understand the phenomena of acceleration in development only when we begin by assuming that the char- acteristics last introduced in the history of any type were more suitable to the new conditions of life on the horizon of occurrence of the species than those which characterized the same stock in preceding horizons. These characters would then necessarily, on account of their greater usefulness and superior adaptability, interfere with the development of the less useful ancestral stages, and thus tend to replace them."34 Two important additions to this law of acceleration were made by the distinguished American naturalist, Cope, who presented an independent formulation of the law itself in the year 186638-±-a year significant for recapitulation, for as has been noted, it gave expression to three original statements of the law, namely, those of Haeckel, Hyatt, and Cope.:' One of « Genesis of the Arietidae, Smithsonian Contributions to Knowledge, 1890, pref- ace "Ibid., p. 40, footnote. MJWd., pp. 44, 45. « Primary Factors of Evolution, 1896, p. 9. The Recapitulation Theory in Biology 25 these added ideas was that of unequal acceleration, concerning which Cope makes this statement: "The acceleration in the assumption of a character, progressing more rapidly than the same in another character, must soon produce, in a type whose stages were once the exact parallel of a permanent lower form, the condition of inexact paral- lelism. As all the more comprehensive groups present this relation to each other, we are compelled to believe that accelera- tion has been the principle of their successive evolution during the long ages of geological time."36 Two other extracts from another writer will show more fully the meaning of this principle: "A character useful to the immature form will have a tendency to be inherited at an earlier age than those useful only to the adult, and so by unequal acceleration of development the parallel between ontogeny and phylogeny is broken"; and this unequal acceleration is especially to be expected "in the larval and adolescent periods where the shortness of the time of development causes throwing together of characters that were not contemporaneous in the ancestors, and where the small size and general habits prevent differentiation of organs that in the correlative adult forms were highly developed . . . "" The other idea added to the law of acceleration was named by Cope "retardation." "Where characters which appear latest in embryonic history are lost, we have simple retardation, that is, the animal in suc- cessive generations fails to grow up to the highest point of com- pletion, falling further and further back, thus presenting an in- creasingly slower growth in the special direction in question."** This gives rise to retrogressive series in evolving forms in contrast with progressive series resulting from the effect of acceleration. The bearing of these principles of acceleration, unequal ac- celeration, and retardation upon the theory of recapitulation has now to be indicated. If acceleration should operate uni- formly upon lines of descent without obstruction, plainly the »• Origin of the Fittest, p. 142. " J. P. Smith, Journ. of Geology, Vol. 8, 1900, p. 417. •* Origin of the Fittest, p. 13. 26 The Recapitulation Theory and Human Infancy ontogeny of a descendant would be a perfectly repeated se- quence of the succession of its adult ancestors, except where the most ancient forms would have been suppressed or omitted from the earliest corresponding embryonic period. This is Cope's " exact parallelism." It would also have the effect of condensing stages without confusing the ancestral order in certain portions of the ontogeny. In case of simple retardation the ontogeny would fail to repeat the most ancient forms, would repeat faithfully the later forms up to the point where the re- tardation left off, and would then fail to repeat stages which the ancestry had recently lost by retardation or successive failure to complete its life cycle. Unequal acceleration would have the effect of "telescoping," or bringing together, stages in ontogeny which had been successive in phylogeny, and to locate later phylogenetic stages before earlier ones. It is ob- vious that, theoretically, this last could confuse the phylogenetic order hopelessly or could even reverse it. The relative importance of these several principles, and the validity of recapitulation, becomes therefore a matter of fact. On this point we can but quote competent authority: " . . . . there are so many species and genera in the various groups of invertebrates whose ontogeny is simple, progressive, and fairly complete, and whose stages of growth are almost exact repetitions of successive antecedent genera, that it would be impossible to find a student of morphogeny of the brachiopods, the marine mollusks, or the lower crustaceans, that does not believe implicitly in the value of larval stages of these groups as records of their family history."39 "In the Cephalapoda, Pelecypoda, Gastropoda, Brachiopoda, Trilobita, Bryozoa, Graptolites, Echinoderms, and Corals, ex- amples are pointed out in which there is clear and unmistak- able evidence of recapitulation."40 Hyatt and Cope adduced certain illustrations of accelera- tion and retardation with man and other vertebrates, but since the more recent writers do not emphasize these, it may be as- sumed that the case for recapitulation rests for the group of students here referred to chiefly upon the examples among the invertebrates. J. P. Smith, loc. cit., p. 422. Cumings, loc. cit., p. 337. The Recapitulation Theory in Biology 27 A point of importance emphasized by Cumings deserves notice here: "... .the Hyatt school of paleontologists have based their phylogenies on epembryonic [i. e., larval] rather than embryonic stages .... since in the nature of the case the true embryonic stages are scarcely ever accessible to the student of fossils .... There arises here a question of definition, does the biogenetic law mean that the ontogeny is a recapitulation of the phylogeny, or does it mean that the embryogeny is a recapitulation of the phylogeny?" "In most of these cases [those listed in the second paragraph above] it is the epembryonic and not the embryonic stages that are the basis of comparison."41 In concluding this report of the bearing of acceleration and retardation upon recapitulation, it will be well to refer to a significant caution contained in Cope's discussion of "inexact parallelism." It has been noted that Cope used this expression in part to refer to a lack of correspondence between any ontogeny and its own restricted line of descent. But he used it also to cover a lack of correspondence between an ontogeny of one line of descent and forms in parallel lines of greater or less kin- ship by reason of ancestors at different points of remoteness in the past. Thus, "So soon as new subordinate characters are assumed.... the parallelism becomes "inexact," and such is the kind of parallelism usually observed. And it is the more inexact the more widely removed in relationship are the forms compared. Thus the parallelism between the embryo man with five branchial slits, and the adult shark, it is very inexact; but that between a true fish and a shark is much less inexact. That between a higher and a lower shark is still more exact, and so on." "As we compare species which are more and more different the more necessarily must we confine the assertion of parallelism to single parts of the animals and less to the whole animal."42 It appears, therefore, that in the cases of perfect acceleration we have just those conditions required by the logic of the theory of recapitulation in its extreme form. They illustrate nicely the modifications "at a not early age" that Darwin saw were needed for a genetic explanation of von Baer's law, and they fall into Fritz Miiller's second class of cases. The evidence « Loc. cit.. pp. 306, 337. «i Primary Factors in Evolution, 1896, pp. 200. 207. 28 The Recapitulation Theory and Human Infancy and the authority of the writers quoted in this section leave no question of the actuality of many examples of more or less close recapitulation among the invertebrates, at least for shell characteristics as such, and for whole organisms to the extent shells are illustrative of the entire structure of the animal.43 Just how general this recapitulation is does not appear, probab- ly this can not be known as yet. The gist of the contentions of the writers in this field seems to be nothing more than that 4 recapitulation constitutes a working principle for genetic classi- fication of very genuine usefulness. There is no disposition to make of it, at the present time at least, a principle of universal application. It is plain that generalizations carried over from this rather circumscribed field of fact to the vertebrate or human territory, and more especially to the human nervous system or mind, can be the sheerest hypothetical possibilities, in view of the complexity of the facts upon this field of their clearest embodiment and of the possible and probable very un- like conditions that have surrounded the evolution of the high- er vertebrate forms. 12. The Facts of Recapitulation. The sketch of the history of the idea of recapitulation thus far drawn shows that speculation and deduction have had no small part in its formulation. The purpose of the present section is to refer somewhat independently to the facts that have been adduced in its support at different times and by various writers. These facts are found to fall into three classes: (a) those derived from a comparison of known ontogenetic and palaeontological data; (b) those of embryonic resemblance among existing types; (c) those of stages or features in ontogeny showing resemblance to stages or features so common to lower allied living groups as to raise the question of an ancestral re- lationship. The facts of the first group are unequivocal in their significance. Either the parallel exists or does not exist when ontogeny and phylogeny are known and accurately com- pared. The other two types of fact are open to alternative explanations, and give ground for controversy, as we shall see. «» "The Mollusks would seem, at first sight, bound to supply us with exact phylo- genetic documents by reason of the abundance of their calccrous shells in all geological strata. But. . . the shell is a moiphological organ of little importance." Depgret. loc. cit., p. 48. The Recapitulation Theory in Biology 29 (a) The Facts of Palaeontology. In the discussion of the views of Darwin reference was made to his expressed sympathy for the belief of Agassiz in the embryonic character of extinct forms. As late as the year 1872 Darwin said, "We may hope hereafter to see this law proved true." Commenting on this point an eminent Eng- lish embryologist, Sedgwick, says, "But as Huxley has shown and as the whole course of palaeontological investigation has demonstrated, no such statement can be made. The extinct forms of life are very similar to those now existing and there is nothing specially embryonic about them. So that the facts, as we know them, lend no support to theory."" The reference to Huxley in this quotation is made to papers written in the years 1855 and 1862. In the second paper Huxley wrote "An impartial survey of positively ascertained truth then negatives the common doctrines of progressive modification, or a neces- sary progress from more or less embryonic forms .... it either shows us no evidence of any such modification or demon- strates it to have been very slight."45 Passing the question as to whether Huxley's views may have undergone a change of emphasis later with the accession of new facts, we may compare with the statement of Sedgwick the opinions of a distinguished German palaeontologist. Zittel, writing on Palaeontology and the Biogenetic Law, in 1895, says, after referring to the immense advantages that would accrue to palaeontology if this law could be strictly used, "If we consult palaeontology, it shows that these surmises are by no means confirmed. There are, indeed, a great number of fossil genera which retain throughout life the embryonic, or, rather, the youthful characters of their existing allies, but it is only among the mammals, and to some extent among the rep- tiles, that I could name a complete series of forms following one another in time and belonging to the same line of development. The Eocene, Oligocene, and, in part also, even the Miocene Mammalia stand to their now existing allies, for the most part, in the relation of youthful forms, while they, almost without exception, exhibit at least some characters which are quickly passed through by their geologically younger successors in the embryonic or youthful stage. The ontogeny of organisms now « In Darwin and Modern Science, 1909, p. 174. « Scientific Memoirs, Vol. II, p. 528. 30 The Recapitulation Theory and Human Infancy living would, for the rest, afford but an unsafe basis for the reconstruction of ancient faunas and floras, since experience teaches that the biogenetic law is frequently veiled or completely obscured owing to various causes." Concluding a series of illustrations of the absurdities to follow from an unchecked use of the law this authority remarks that these few instances "may suffice to show how trivial are the discoveries concerning existence in earlier periods of earth- history that can follow from ontogenetic researches alone."46 Cope and others were interested in collecting particular in- stances of recapitulation and these appear in the text-books. They are conveniently presented by Woodward in the follow- ing paragraph: "There is no doubt, for example, that in the course of the individual development the homocercal tail of a modern bony fish passes through the same stages as those successively ex- hibited by the majority of the adult fishes at the different geo- logical epochs. It is also evident that the family of deer (Cer- vidae) has gradually acquired complex antlers in precisely the same manner as every modern stag acquires them during the course of its individual life. Again the "cloven foot" of the existing ruminant appears in the embryo with separated meta- podial bones, like those of the adult ancestral ruminants. It is also tolerably certain (though fossils have not yet provided absolute demonstration) that the rudimentary teeth and hind limbs of the existing whale bone whales (Mystacoceti) are in- herited from functionally toothed quadrupedal ancestors."47 In Osborn's "Evolution of Mammalian Molar Teeth" this example of recapitulation is to be found, "In the lower molar teeth the order of calcification is precisely the order of evolution So we find that the order of embryonic development exactly repeats the order of historical development .... But this .... is not exactly the case in the upper molars. Nevertheless, out of eight cusps in the upper and lower molars considered together, six cusps calcify in the order in which they were successively added to the single reptilian cone."48 And from the same authority — this note, "The recent discovery of the modes of origin of the horns in the titanotheres, a perissodactyl group remotely related to « Natural Science, Vol. 6, 1895: pp. 308, 309. «j Outlines of Vertebrate Palaeontology, 1898, p. xxili. «» p. 65. The Recapitulation Theory in Biology 31 horses, tapirs, and rhinoceroses, permits of a comparison of phylogenesis with the ontogenesis of the horns in bovine mam- mals— the conclusion is that ontogeny closely recapitulates phylogeny, that the genesis is gradual or continuous, that the horns arise definitely and determinately."49 As is well known the ancestry of the horse is one of the few vertebrate ancestries' that have been reconstructed on palaeon- tological evidence, and it is therefore of peculiar interest to note the results of a comparison of the embryogeny of the horse with its racial history. This comparison has been made in part by Ewart, who, in the course of his report, raises and answers this question, "What evidence is afforded by the horse in favour of the re- capitulation theory? Evidently if the reservations made on the plea of abbreviation in development, etc., are almost unlimited, a very remote re- semblance in an embryo to a supposed ancestor might be con- sidered sufficient evidence of recapitulation .... There must, however, be some limit to the use of the word recapitulation .... Recapitulation, if it means anything at all, must be held to mean that, say in the case of the horse, the embryo should after a time not only resemble the unknown embryos of its extinct ancestors, but that it should resemble the fully-developed ancestors. This implies that during its ontogeny the horse should not only ad- vance in a zigzag fashion along the trunk of the animal tree, but also when it reached its own particular branch that it should during its onward course make deflections in the direction of Hyracotherium, Mesohippus, etc., until having, at a respectful distance, done hurried homage to its ancestors, it at last reaches its final goal, and presents its true characters .... It is impos- sible with any degree of accuracy, either to speak of a Hyraco- therium or a Mesohippus stage, or even of a Hipparion stage. If, on the other hand, all that is meant by recapitulation is that the developmental record of any given form is represented by a series of zigzags or curves instead of a straight line, the horse may be claimed as supporting it. As is to be expected in forms that have evidently descended from the same ancestors, there is a certain amount of agreement between horse embryos and the so-called fossil horses; and were it possible to know the development of these extinct forms, the points of agreement would be doubtless increased. Further, as might also have been expected, the points of agreement become more numerous and more evident as Hipparion — a not very ancient form — is reached. Science, Vol. XXXV, 1912, pp. 595, 596. 32 The Recapitulation Theory and Human Infancy So much is this the case, now that we know the second and fourth digits are for a time fairly well developed, we might speak of a Hipparion stage in the ontogeny of the horse. To admit that the horse, before assuming its own specific characters, makes, as it were, a deflection towards the not very ancient form Hipparion, is hardly going far enough to justify the assertion that the horse during its development assumes, one after another, the charac- ters of its ancestors, or, in other words, except in the most limit- ed sense, 'climbs its own ancestral tree.'"80 Deperet, in the book to which reference has already been made, not only presents an authoritative appraisement of the embry- ological method of determining phylogenies, from the viewpoint of palaeontology, but gives also a convenient summary of the amount of correspondence of ontogeny with phylogeny as determined from this same viewpoint: "Has Palaeontology completely confirmed the conclusions thus drawn from the embryology of existing beings? We may approach this important question by two different methods. The first method, which is the oldest and the one most generally employed, consists in finding in geological strata forms which in the adult state reproduce one of the transitory phases through which the development of an existing animal passes. We give to these fossil forms the name of Persistent Embryonic types. Palaeontology is able to furnish us with a fairly large number of examples of this. Thus the Fishes of the Primary epoch, such as the scaly Ganoids, have a soft vertebral column in a state of embryonic tissue or notocord, as in the existing Ganoids or Teleo- steans .... In the same way the Palaeozoic Amphibians pass, as regards the ossification of the vertebral column, through a series of progressive phases. . . . These different phases are reproduced in the development of our present Reptiles and Amphibians. In recent and modern Ruminants the bones of the metacarpus and of the metatarsus, separate in the embryo and the young animal, become welded later in the adult into a cannon-bone caused by the fusion of the two metapods. We know among the early Ruminants genera. . . .in which the metacarpaland the metatarsal bones remain distinct in the adult state. "We may also quote a few persistent types among the Inverte- brates "But it must be clearly stated that these examples of representa- tion in fossil adult species of the embryonic, or more correctly, of the youthful characteristics of existing animals, cannot be «Ewart. Journ. Anat. and Phys., Vol. XXVIII, 1893-94, pp. 348-350. The Recapitulation Theory in Biology 33 generalized, and that they remain up till now in the state of exceptional facts."51 The second mode of answering the question is that of studying the development of fossils themselves, and this has been re- ported in the earlier section dealing with the laws of accelera- tion and retardation. The evidence for recapitulation there presented belongs in character with that just cited. With the exception of this last group of facts relating to the shells of invertebrates the authorities quoted are in general agreement. We must conclude that the palaeontological evi- dence for recapitulation is not impressive. Among certain groups of animals in some part of their history, some forms are embryonic in a broad way, and a considerable number of particular instances of the embryonic or youthful retention of ancestral adult traces are noted. Apparently the conditions favoring recapitulation in fossil shells are peculiar to such char- acters. (6) The Facts of Embryonic Resemblance. The historical importance of von Baer's law for the present topic has been obvious enough. Darwin, Haeckel, and Spen- cer either made it the point of departure of their arguments or drew heavily upon it. Spencer showed clearly in the words quoted from him that a consistent evolutionary application of the law is equivalent to recapitulation. But the limitations of the formula were noticed very early. Darwin alluded to the common, but not invariable, resemblance between embryos in the same class. Fritz Miiller speaks of "developmental forms now so totally different in the nearest allies, now so surpris- ingly similar in members of the most distant groups."52 Spen- cer regarded the generalization as an average truth only. Haeckel and others found great difficulty in reducing to an order consistent with the law the observed differences between com- parable embryonic stages. The following extracts will indicate the attitude of more recent writers toward the facts in question : "Von Baer's statement appears to be erroneous from a modern point of view in the following respects. We know that in certain large groups some forms develop in a very different way from «i pp. 254-256. *i For Darwin, p. 97. 34 The Recapitulation Theory and Human Infancy that followed by other members of the group .... Again, it is entirely arbitrary to assume that the group-characters are the first to appear, and then successively those of the order, family, genus, species. Finally .... we do not find early embryos of a group identical, for with a sufficient knowledge of the develop- ment it is always possible to distinguish between the embryos of different species, as well as between adults, only it is more difficult to do so, because the embryonic forms are simpler."53 In a study made in 1894 Sedgwick put the law to test by making comparisons between embryos of closely allied animals and embryos of animals remotely related. The observed facts did not substantiate the law.64 Sedgwick's more recent state- ment is as follows: "The law asserts that embryos of different species of animals of the same group are more alike than the adults and that, the younger the embryo, the greater are the resemblances. If this law could be established it would undoubtedly be a strong argu- ment in favor of the "recapitulation" explanation of the facts of embryology. But its truth has been seriously disputed. If it were true we should expect to find that the embryos of closely similar species would be indistinguishable from one another, but this is notoriously not the case. It is more difficult to meet the assertion when it is made in the form given above, for here we are dealing with matters of opinion. For instance, no one would deny that the embryo of a dogfish is different from the embryo of a rabbit, but there is room for difference of opinion when it is asserted that the difference is less than the difference between an adult dogfish and an adult rabbit. It would be perfectly true to say that the differences between the embryos concern other organs more than do the differences between the adults, but who is prepared to affirm that the presence of a cephalic coelom and of cranial segments, of external gills, of six gill slits, of the kidney tubes opening into the muscle-plate coelom, of an enormous yolk-sack, of a neurenteric canal, and the absence of any trace of an amnion, of an allantois, and of a primitive streak are not morphological facts of as high an import as those implied by the differences between the adults? The generalization undoubtedly had its origin in the fact that there is what may be called a family resemblance between embryos and larvae, but this resemblance, which is by no means exact, is largely superfi- cial and does not extend to anatomical detail."65 From these authoritative statements it appears that the facts of embryonic resemblances fail to support recapitulation M Morgan, loc. cit., pp. 74, 75. H Quart. Journ. of Micros. Sci. Vol. 38, N. S., 1894, pp. 35-52. " Darwin and Modern Science, p. 175. The Recapitulation Theory in Biology 35 in all three of its main implications. The order of appearance of characters is not uniformly, or even commonly, that required by recapitulation, which is first those representative of the order, and then in succession, of the family, genus, species. In the second place, embryonic resemblance in comparable stages does not vary directly with remoteness of kinship, but shows often very great divergence from this rule, indicating unlike careers in lines of descent in the same group and there- fore great diversity in the appearance of variation during de- velopment, at any period, and not only at the adolescent or adult end of ontogeny. Finally, where resemblance does ex- ist, it is not identity, nor even close, implying that the effect of variation upon the same ancestral structure has not been the same in allied lines of descent, but has been productive of new structures, suggesting perhaps in broad outlines the an- cestral structure, but still variant in every case, and essenti- ally so. What is left for von Baer's law is the "family resemblance." But family resemblance does not imply recapitulation. It means at most a common ancestor.56 This common ancestor may have had his ontogeny determined in any way, recapit- ulatory or other. That this family resemblance may often be striking without implying recapitulation is well shown in a recent statement. The Nauplius larva is common to many Crustacea. "But it is not in the least justifiable to deduce, as some have attempted, that the Nauplius larva represents the adult ancestral form from which the Crustacea as a whole have sprung." " The Zoaea larva is similarly characteristic of many widely separated Crustacean groups, nevertheless "it cannot possibly be looked upon as representing the adult an- cestral type of these animals." a Again, "A larval form, yet more widely spread than either of the Crustacean larvae mentioned, is the Troehosphere larva, characteristic of Annelids of all kinds and curiously enough of some Mollusks .... which in the adult state are entirely *« " When we recognize a larval or embryonal form as characteristic for a whole animal group, we may not conclude therefrom that necessarily a similar phylogenetic stage is represented by the same. We are justified only in the conclusion that the ancestral foim of this animal group had possessed that characteristic developmental stage." Hatschek, quoted by Montgomeiy. loc. cit., p. 185. « Smith, Primitive Animals, 1912, p. 64. M Ibid., p. 65. 36 The Recapitulation Theory and Human Infancy different in their whole organization from worms of any de- scriptive. This fact implies that the Trochosphere is an ex- ceedingly ancient type of larva, which must have been possessed at some period by the common ancestor of the Annelids and Mol- lusks . . . There is however nothing to support the view that the Trochosphere in any way represents the common an- cestor of the Annelids and Mollusks. . ."59 "We cannot however press the argument too far and say that no larval form ever represents an adult ancestral form. Every case must be judged on its own merits after taking into account all the available evidence to be derived from the com- parative study of related forms. Thus it seems indubitable that the so-called Mysis larva, a stage assumed by [many mem- bers of a group of Crustaceans] after the Zoaea .... does very closely represent an adult ancestral form, the actual ex- istence of which is nearly realized by the primitive Anaspides and Schizopod shrimps. Here we are dealing with a late larval form just before the adult structure is attained, and it would appear not to have had time to have been profoundly modified in accordance with larval existence. It would seem, therefore, that we are more likely to meet with actual adult ancestral types in the late larval or developmental stages of fairly closely related animals, which have not had time to be secondarily modified, than in the very early stages of more remotely related forms, although these, in accordance with von Baer's law, may show many points of resemblance which are lost in the adults."60 The writer from whom these sentences are taken is able to accept von Baer's law by a loose construction of it: "his [von Baer's] statement was that in any two or more related animals the further back we go in their developmental history from the egg the more do they resemble one another. In this form it must be admitted that von Baer's law holds good with very few exceptions "61 This statement may be compared with those of the author- ities already quoted. It appears that even on this loose con- struction of the meaning of von Baer's formulae there is no settled unanimity of opinion among biologists. These dis- crepancies, however, do not affect the essential significance of the law for recapitulation, for as to this all the writers quoted agree in that embryonic likenesses do not of themselves imply •• Smith, Primitive Animals, 1912, pp. 68, 70. «» Ibid., pp. 66-68. •' Ibid., p. 58. The Recapitulation Theory in Biology 37 a law of recapitulation, but at most only the retention of ances- tral forms. Whether these are to be regarded as embryonic or adult forms is a matter for study in each case. (c) The Facts of Comparative Morphology. The third type of evidence for recapitulation, that involving a comparison of ontogenetic stages with forms common to "low- er" existing groups, may now be referred to. There are, first, those phases in the very early embryonic development of Met- azoa suggestive of a progression from the unicellular condition, and in the development of Chordata, from the simple metazoon form to the chordate and vertebrate condition. The case for recapitulation on these lines is well stated by Dendy in his recent text-book. "We have already referred. . . .to some of the earlier stages in the development of that primitive fish-like animal Amphioxus. Let us next enquire how these stages may be interpreted in accor- dance with the recapitulation hypothesis. The unicellular ovum obviously represents the remote protozoon ancestors which were common to the whole animal kingdom, and which are also represented at the present day by independent unicellular or- ganisms such as the Amoeba. The segmentation of the ovum into primitive embryonic cells or blastomeres represents the transition from the condition of the simple protozoon to that of the protozoon colony, in which the individual cells, instead of separating, as in the dividing Amoeba, remain together, but still without undergoing any marked differentiation and division of labor. The arrangement of the blastomeres in the form of a hollow sphere, the blastula or blastosphere, with a single layer of cells surrounding a central cavity, represents the formation of such a protozoon colony as we see in the existing Volvox or Sphaerozoum. The process of gastrulation, whereby the single- layered blastula is converted into a two-layered gastmla, with primitive digestive cavity (enteron) and primitive mouth (blas- topore) represents the transition from the protozoon colony to the coelenterate stage of evolution, the latter being still repre- sented at the present day by such forms as Hydra, Obelia, the jelly-fish, the corals, and all their numerous relations, which retain in their organization all the essential features of the gastru- la, though generally complicated by the development of tentacles, skeleton, etc. The development of the coelomic pouches as outgrowths of the primitive digestive cavity, and the conversion of these into mesoblastic somites, arranged serially or metameri- cally down each side of the body, mark the transition from the unsegmented and coelenterate condition to the metamerically 38 The Recapitulation Theory and Human Infancy segmented and coelomate condition. The cavities of the coelo- mic pouches form the coelom or body cavity, which is at first transversely sub-divided into compartments, as it still is in the adult earthworm, while their walls form the third germ-layer or meso-blast, lying between the epiblast which covers the sur- face of the body and the hypoblast which lines the digestive cavity. Along the mid-dorsal line of the body a strip of epi- blast sinks down and becomes folded into the form of a tube, the rudiment of the central nervous system (brain and spinal cord) and beneath this tube a long strip of hypoblast becomes nipped off from the roof of the gut, forming the notocord or axial skele- tal rod — the foundation around which in higher types the verte- bral column is built up. A little later the front part of the gut becomes pierced by gill-slits for purposes of respiration and the primitive chordate condition is thus fully attained. Amphioxus does not progress much beyond this stage in its development .... Amphioxus is a chordate animal but it is not a true vertebrate. It probably, however, represents fairly close- ly a stage of evolution through which the ancestors of the verte- brates have passed, though it becomes somewhat modified by secondary features in the later stages of its development."62 In the case of man Haeckel carried the series beyond that represented by Amphioxus through three stages, the cyclostoma, the ichthyoda, and the amniote, making ten stages in all re- presenting an ontogenetic-phylogenetic correspondence.68 But as suggested above in the account of HaeckePs part in the for- mulation of the theory of recapitulation, the ancestral refer- ence in the higher stages is often to ontogenetic conditions in lower forms, making the adult phylogenetic equivalence in such stages indirect, to say the least. It is significant, by the way, that the chief exponent of recap- itulation is able to present an ontogenetic-phylogenetic cor- respondence of ten stages only. When it is considered that on the phylogenetic side the sequence occupied millions of years and proceeded through an almost indefinite number of special forms, the limitations of a conception of ontogeny as illus- trative of the chronological sequence of ancestors become fairly obvious. It is almost impossible to report biological opinion as to the significance of the kind of fact now referred to, so various are the views held regarding it. One can merely set the outside •« Outlines of Evolutionary Biology, 1912, pp. 265-267. •> Evolution of Man (5th ed. trans.), pp. 547-550. The Recapitulation Theory in Biology 39 limits within which it ranges. These are represented at one end by the views of Dendy and Haeckel, as indicated, and those of the palaeontologist, Deperet, at the other. The latter re- fers to Haeckel's hypothetical ancestors as "visions of the mind" because no fossil evidence can be offered for them. It is probably true that most naturalists and embryologists do not wholly discount the phylogenetic significance of the series of early embryonic stages among the Metazoa, and are willing to admit that it may possibly represent in a very gen- eralized fashion what actually happened in the early evolution of organic forms. It may be well, however, to report here a recent conservative statement apparently aimed directly at the type of discussion illustrated in the quotation from Dendy just given: "... .in the present state of knowledge we are able to separate the various components of the animal kingdom into a certain number of divergent groups or phyla; and that within the limits of these phyla, although we are far from knowing even approxi- mately in every case the course evolution has followed, yet we are safe in concluding that all the diverse ramifications have originated in the remote past from one common source, or type. But when we attempt to go behind the phyla and discover their origin and inter-relationships, we leave the firm ground alto- gether and wander in a slippery and nebulous region of specula- tion. It is true that certain hypotheses of a plausible character have been suggested which have satisfied uncritical minds, and which we often hear advanced as a part of ascertained science and accepted in an otiose spirit. We are urged to believe that life "originated" in certain chemical compounds which on attaining a certain degree of complexity began to exhibit the fundamental properties of life; and from these comparatively structureless masses the nucleated cell was evolved and the unicellular animals and plants, the Protozoa and Protophyta, made their appearance ; that these gave rise to cell colonies, the Metaphyta on the one hand, and the Metazoa on the other. The Coelenterate type of organization is presented to us as the form in which the early Metazoa had their being, and from this by the addition of the mesoderm we arrive at the Platyhelmia, and from them by the addition of a coelom and of metameric segmentation at the seg- mented Annelid. And so by the addition and subtraction of their characteristic qualities we may pass in imagination from one fundamental type to another; but what is there of reality in these speculations? They rest not on any objective evidence 40 The Recapitulation Theory and Human Infancy but upon the tendency of the mind to pass from the apparently simple to the manifestly complex, and to regard the former as primitive and ancestral and the latter as secondary and deriva- tive."64 Another class of facts representing this third type of evidence for recapitulation is made up of certain profound metamor- phoses observable in the development of certain groups possess- ing larvae which recall in a rather striking way the ancient forms from which groups in question are believed to be descend- ed. These facts bear unmistakable evidence to a course of evolution in parts of some lines of descent, in which variations or mutations leading to the higher form have supervened em- phatically at the adult end of the ontogeny. Ordinarily these larvae have been adapted in important ways to the special conditions of their life as larvae, but not so seriously as to wholly obscure the ancient structures upon which the adaptations took place. These larval forms are untrue to the ancient pattern also by virtue of the fact that they are transient, con- stantly progressing in the direction of the adult condition, and their organization is therefore disposed in part with refer- ence to the demands of the future. The customary example is the familiar metamorphosis of the common frog. Similar cases are found among the ascidians, the crustaceans, the in- sects, the flat fishes. The only way in which the ancestral reference in these cases is denied is by so minimizing the resem- blance to the ancient form that the recapitulation is said to be wholly superficial and lacking in real significance. This has been done by a few extreme critics of the recapitulation theory. Currect opinion of this class of facts is reported below. Finally these are those rudiments and isolated special char- acters in the embryos of higher vertebrates which recall sim- ilar characters and conditions in the adults of lower vertebrate forms. These are referred to by Sedgwick as follows: "... .the embryos of the higher vertebrate possess in the struc- ture of the pharynx and of the heart and vascular system cer- tain features — namely, paired pharyngeal apertures, a simple tubular heart, and a single ventral aorta giving off right and left •« Smith, Primitive Animals, pp. 14 et se« Play of Animals, trans. 1898, preface, p. xx, and p. 75. Human Infancy and the Recapitulation Theory 71 survival. This degree of efficiency involves some practice in all learning animals and in many a long continuation of it. This indispensable practice would be fatal if left to the period of independence. It might conceivably have been enforced by parents, as it is to a very slight extent among animals, but this implies a degree of intelligence and foresight beyond the capacity of animal parents, indeed not easily assumed by civilized human parents with all their higher resources. Self-imposed practice, or play, was therefore the simplest biological expedient. If the formula of Groos be understood to assert that infancy without play is useless, its truth must be admitted, and it is fair to assume that infancy and play evolved together. A merely docile plastic- ity could scarcely give rise to the habits of maturity. Play is the necessary middle term between plasticity on the one hand and intelligence on the other. These several additions to the ideas of Fiske are brought to- gether in Baldwin's "Development and Evolution" (1902), per- haps without explicit reference to their bearing upon a theory of infancy as such. Their interrelations are, however, there shown. The doctrine of "organic selection," also reported in this book, is not without its implications for the present topic.17 This theory was presented by three writers independently — Osborn, Lloyd Morgan, and Baldwin — and has obtained a fairly general acceptance. Its general effect is to show how plasticity has determined in part the selection of non-plastic or fixed or- ganic characters. It must have been noticed in the reported statements of Fiske that the evolution of both reflex or instinc- tive and intelligent behavior was explained in terms of use- inheritance. This explanation was not inconsistent with the views prevailing at the time Fiske wrote, but has come to be no longer tenable by reason of the change of emphasis since regard- ing the transmission of acquired characteristics. It was inevi- table that plasticity and its effects should be made to accord with the more acceptable doctrine of the germinal origin of variation and mutation. Organic selection assumes that although plasticity is physically inherited its resulting habits are not. But these habits, because of their effect in making adaptations more adequate, would 17 See Appendix B for the original statements with others. 72 The Recapitulation Theory and Human Infancy often have life-saving value as such, and would therefore in the long run preserve and select individuals in whom the fixed and physically inherited germinal variations should increase in the direction of better adaptations. Plasticity and its habits would thus blaze the way along which germinal evolution could follow, because the incidence of natural selection would fall first upon habits and only through them upon the physical make-up of the animal. With the rise of tradition the value of this process would increase, so that on higher simian levels and early human levels the selection of hereditary strains was increasingly deter- mined by the character of the social habits directly or indirectly favoring survival and leaving of offspring. Infancy being es- pecially responsible for the assumption of habits, in this manner becomes intimately related to organic evolution to the extent that the theory of organic selection is true. In the light of these later contributions, Fiske's original state- ment of the theory of infancy requires some amplifying. The biological explanation of infancy assumes that with this period is associated species preservation and success, and in the case of man, species dominance. The advantages accruing to species because of infancy reside in the greater adaptability of individu- ally acquired habits over the mechanical behavior of instinct. This is made possible by an elaboration of the central nervous system, especially in the cerebral portions. But the accumula- tion of habits requires time and practice and a degree of ineffi- ciency and dependence corresponding to the difference at any time obtaining between the neuro-muscular condition of the young and that of the adult. Among the higher primates these habits are in large part socially derived, calling for the psycho- physical adjustments of suggestion and imitation on the part of infancy to insure their transmission. The inefficiency of infancy necessitates counterbalancing parental oversight, and the indis- pensable practice is obtained by imposing upon the young an instinctive need of self-exercise or play. This spontaneous exercise is directed not only upon well-defined tendencies char- acteristic of the adult life of the species in need of perfecting, but also to modes of social action resting slightly upon an instinctive basis and more largely acquired by successive generations in re- sponse to the changing conditions of their lives. Play is there- fore both specific in its forms and broadly imitative and general- Human Infancy and the Recapitulation Theory 73 ized. As to its origin, plasticity is characteristic in small degree of animals other than the higher mammals, but mutations in this direction with their coincident delayed maturity were futile until accompanied by the protection of parents. Plasticity is for this reason conspicuous with mammals. In turn the assump- tion of valuable habits had the effect of preserving and selecting germinal mutations in a given direction which would otherwise have been sacrificed. Finally, the vital energy necessary to the production of organic complexity in the higher learning animals was made possible in some part by the saving from a lowered birth-rate due to the increasing parental care and solicitude given to the eggs and the immature young.18 Two recent volumes from the pens of accomplished naturalists discuss the infancy and youth of animals in a convenient and exceedingly attractive fashion.19 In the main these books con- firm the earlier accounts, but with important minor qualifications. The economic value of parental care as a substitute for great fertility in biological competition is accepted and illustrated by both writers. Pycraft, however, refers to "some puzzling facts" and rejects the view which finds in the mortality of young a cause of exaggerated fertility. Rather, it should be said, fertility encourages mortality by offering large numbers of young for food. Fertility, like extravagance in ornament and gorgeousness of color, is to be regarded as a specific character and not a direct response to biological necessity. Moreover, the relation of fertility to mortality can often be only surmised, from ignorance of the actual natural conditions surrounding many species. It still does not appear that Pycraft's position need be in essential contradiction to the older way of stating the matter, which perhaps failed to clearly affirm that the only effect of selection was the limitation or survival or inherent specific characters. There seems to be small reason for doubting the broad correlation of decreasing fertility and degree of parental care in relation to u The following extract from Washburn's Animal Mind, 1908, p. 284, should be reported in this general connection: " One of the most vital meanings of the long period of helplessness and dependence constituting human infancy lies in the fact that by relieving from the necessity of attending exclusively to external objects, it renders possible attention to the sensations resulting from movement; and thus, by supplying an essential condition for the revival of such sensations in idea, it opens the way for the control of movement through the movement idea." The extract should be read with its context. u Mitchell, The Childhood of Animals, 1912. Pycraft, The Infancy of Animals, 1913. 74 The Recapitulation Theory and Human Infancy mortality, provided it be understood that natural selection need not always have produced an exact or refined adaptation. The value of parental care as a necessary condition to the emer- gence of organisms of the higher types and the correspondence of youthfulness with this higher organization is also acknowl- edged by both writers. The greater capacity of the higher ani- mals with the prolonged infancy period is due to a more or less extensive education to fit them for the strenuous activities of their life. This education varies with the different groups and conforms to the necessities of circumstances and the mode of living. To play is attributed a large importance in the prose- cution of this education, and it is interesting to note that on the mooted question as to whether young animals learn directly from their parents both authorities speak with certainty in the affirmative. Mitchell's description of imitation below the mon- keys is, however, a carefully guarded one, and amounts to scarcely more than a belief in organic predispositions to trial and error modes of action which are in some degree encouraged and facili- tated by the presence of similar action on the part of others. With the apes this author holds for something akin to human types of conscious imitation. In view of prevailing assumptions regarding the causes of the duration of youth Mitchell's statement in this connection may serve to call attention to the complexity of the facts and yet to show the degree of truth in the assumed parallel between youth- fulness and intelligence in the species. "The duration of youth in all [vertebrates] is settled by no invariable chain of organic necessity. It has no relation to the duration of the complete cycle of life from birth to death. It is linked with size, but only in an indirect fashion, most apparent in animals most akin. It is linked much more closely with complexity of organization, so that the higher forms usually take longer to mature than their near but lower relations. It is linked most closely with intelligence, the more intelligent ani- mals having relatively longer youth. And as we pass down- wards from intelligence to instinct we find that the duration of youth shortens."20 Helplessness in young animals has been very generally identi- fied with the immaturity of neuro-muscular co-ordinations con- " Mitchell, The Childhood of Animals, p. 54. Human Infancy and the Recapitulation Theory 75 stitutive of intelligent or adaptive behavior. It appears from the two accounts now under discussion that other causes may contribute to this condition. The young of many carnivores are thought to be born in their imperfect physical state be- cause the agility required of the mother in catching living prey would be seriously hindered by carrying heavy young. Among nestlings in the less precocious birds helplessness is alleged as a safeguard to premature hazardous beginnings in locomotion. Thus helplessness as a condition due to unlearned adaptive powers is to be distinguished from that induced by other biological needs, as well as from that which may be unrelated to any utility. The helplessness which associates with neuro-muscular plasticity is presumably not a general condition at all, but is relative to the learning that any species may accomplish in those special directions characteristic of it. With regard to recapitulation in the period of infancy Mitchell's statement is as follows: "... the young of nearly allied animals are much more alike than are the adults. . . . We explain this by sup- posing that the evolution of the individual to a certain extent repeats the evolution of the race. . . . We have to re- member, however, that this explanation is not complete, and we shall find many characters of young animals to which it does not apply. The young animal owes its characters not merely to its ancestry; as much as the adult, it has to be fitted to the special environment in which it lives. It is not merely a stage in development, but an independent living creature with its own needs and its own aptitudes, presenting characters that are neither a memory nor an anticipation, neither a relic of the past nor a preparation for the future, but suitable for its own purposes."*1 The tenor of Pycraft's statement is not greatly different : "Time was when it was believed that these early-growth stages, if carefully followed, would reveal all the mysteries of evolution, since, it was supposed, every animal had to climb its own genealogical tree, so to speak. But it was soon found that such hopes were over-sanguine, for records of some of the most important phases have been lost completely, and others blurred; while some of the phenomena have nothing to do with ancestry, 11 Mitchell. The Childhood of Animals, p. 7. 76 The Recapitulation Theory and Human Infancy but represent what we may call scaffolding — features which have been introduced solely for the benefit of the individual. The study of young mammals does, nevertheless, throw a flood of light bearing on their ancestry. . . .'m It must be noted that both writers, by the terms infancy and youth, refer not only to that period of plasticity in the early life of animals of the learning type, but to the period following hatching whether plastic, larval, or merely precocious and essen- tially unmodifiable, as with growing reptiles. If we limit the application of their remarks to the period of plastic neuro-mus- cular development, certain other statements of these authors should be considered. Mitchell, for instance, with reference to the mammals, the group in which the period of plastic infancy is most conspicuous, writes as follows: "Mammals, when they are born or very soon afterwards, closely resemble their parents. The differences are due to greater likeness to ancestors and to their nearest allies, to the absence of special weapons or ornaments, or to the presence of characters useful to the young themselves."28 One gathers that the period of youth among mammals is not essentially recapitulatory but rather adaptive and anticipatory. Nevertheless, both these authors present a very considerable number of youthful characteristics which they explain as re- tained ancestral features. From the account of Pycraft are to be noted the following: certain cases of "milk-teeth"; horns of ruminants; antlers of deer; the presence of a hairy covering which does not persist; the under-fur of one group of seals; spines in certain Insectivora; and the familiar ape-like features of the human infant. Pycraft concludes his list with the remark, "We might add considerably to the number of instances of this kind." In the matter of coloration the case is complicated and some difference of opinion is expressed, yet the two authors agree in the statement that the young of mammals very commonly show differences in coloration when compared with adults, the youthful coloration being regarded by both as older, the adult as a later modification. 12 Mitchell, The Childhood of Animals, p. 40. " Op. cil., p. 13. Human Infancy and the Recapitulation Theory 77 Thus the youth of mammals is not devoid of ancestral features. These may be "recapitulatory" either because they resemble features of the youthful period of the ancestor, or because they represent the actual adult ancestral condition modified in descent. It would be a matter for study in each case. Still, this does not make youth essentially recapitulatory, for these features are comparatively few when measured against the total make- up of the young animal. They exist alongside others which are adapted to the infantile condition as such, and in spite of what is declared to be a close resemblance of young and adult mammals, taking the group as a whole. 3. Recapitulation and Human Infancy. Before undertaking a discussion of the relation of the theory of recapitulation to human infancy — more especially to the mental traits of infancy — it will be well to consider just what may be properly understood by ancestral reference in this connection. It is obvious, hi the first place, that there is nothing to correspond to palaeontological evidence, the court of last resort on the physi- cal side, — unless something of value may be inferred from the structure of fossil skulls. Ancestral allusions to racial mind must be made in the main to what can be inferred legitimately from objective behavior in the scale of living animals, and since these animals are almost universally end-forms in a long process of specialization away from common ancestors, it is clear that inferences as to phyletic mentality are extremely hazardous. If, however, a mental or physical trait peculiar to infancy has a fairly well-defined homolog among lower animals that may be regarded as closely related to probable ancestors, there is ground for assuming an ancestral reference. If the case is one of degree, there must be reasonable certainty of a greater resemblance to the ancestral homolog than to the infant's own adult condition. There will be no justification for assuming an ancestral reference simply because an infantile trait shows some analogy to any animal trait whatever, and surely none merely because no prospective, adult, or adaptive reference can be made. Biological utility is no longer a category of uni- versal application. Heredity is now known to carry much more than the materials of organic adaptations, having laws of its 78 The Recapitulation Theory and Human Infancy own which operate without reference to such adaptations.24 Unfortunately a very considerable number of the examples offered for recapitulation in infancy are merely fanciful or even wholly absurd because of a neglect of these obvious logical require- ments. Unless these limitations are acknowledged the ancestral doctrine of childhood becomes meaningless. For if by recapitula- tion or ancestral reference is meant only that the organized and un- acquired part of the mind is due to its history, without regard to a disparity in kind or degree as between infancy and maturity, this is simply equivalent to declaring that the hereditary part of the human mind is inherited, a statement of little descriptive value. That the recapitulationist has done good service in emphasizing the racial character of mind, whether adult or youth- ful, is not questioned. The point at issue is whether infancy is peculiarly ancestral, that is, older than maturity. A faithful application of the traditional idea of recapitulation to psycho-physical behavior would mean that as the individual develops it will rehearse in a chronological way the chief stages of psycho-physical evolution in the phylogeny, except as this has been disarranged by direct or cenogenic modifications. There rests upon the advocate of this view, then, the necessity of showing that the sequence of developmental stages is really representative of the racial sequence, and that the constituent phases in the progression are truly homologous with the ancient stages and not merely analogous or convergent phenomena. This consistent application of the biological theory has rarely been made to infancy and mental genesis. Recapitulation has taken the form, for instance, of the declaration that the psycho- physical functions appear in the individual in the order of their racial evolution. So stated the doctrine disregards the repre- sentativeness in development of the whole phylogeny. All existing functions may be comparatively recent and many, or even most of them, may have been lost. Those that do appear, however, rise in the phylogenetic order. This view of psycho- physical recapitulation varies from that derived from embryology in another particular, for whereas biological recapitulation assumes that the individual passes through and leaves behind, or radically makes over, its recapitulatory stages in the progression " See Bateson, Problems In Genetics, 1913. Human Infancy and the Recapitulation Theory 79 towards the specific adult form, the view in question has refer- ence merely to the appearance of psycho-physical features, which thereafter remain functional for life; for example, in the statement that the emotions appear in the order of their rise in the race. From these more or less direct applications of the biological theory there is noticeable a grading off to a less and less chrono- logical notion of it, as there is in embryology, until recapitulation is supposed to be illustrated in any juvenile retention of ancestral adult characteristics, or indeed of any ancestral traits whatever, juvenile or adult. However these interpretations of recapitulation may differ, they have in common the idea that infancy is essentially retro- spective, rather than adaptive and preparatory. This idea therefore becomes the chief point of attack in any criticism of the theory of recapitulation in its psycho-physical applications. There is perhaps little profit in attempting to assign to specific writers the different interpretations of psycho-physical recapitu- lation just alluded to. These have not been clearly distinguished in the literature of psycho-genesis, and since the guiding ideas were so directly taken from embryology the history of the dis- cussion there is the really important matter. Romanes seems to have been the first to undertake along inductive lines a detailed comparison of human psycho-genesis with the history of mind as exemplified in existing animals. A glance at the diagram at the beginning of "Mental Evolution in Animals" (1885) will reveal the results of his effort. A glance will suffice also to show its essentially artificial character. The comparison was extended with greater thoroughness in "Mental Evolution in Man" (1889). To the mind of Romanes the dia- gram indicates "in how strikingly quantitative, as well as quali- tative, a manner the development of an individual human mind follows the order of mental evolution in the animal kingdom. "" As is well known, President G. Stanley Hall has had a large part in the extension of the doctrine into the field of infancy and mental genesis, and it is not surprising that his "Adoles- cence" (1904) should assume it throughout. Hall's statements are made with the full admission of cenogenic "distortion," "confusion," etc.; but the underlying adherence to the chrono- « Mental Evolution in Man, p. 5. 80 The Recapitulation Theory and Human Infancy logical conception is unmistakable. One allusion among many is the familiar one to the period of childhood from nine to eleven years as representing "a terminal stage in human development at some post-simian point." This period is followed by adoles- cence "which recapitulates the long pilgrimage of the soul from its old level to a higher maturity which must have taken place in the race in certain of its important lines long before the his- torical period."26 Statements of the kind are legion.27 Two others will serve the present purpose. One is from the biologist Tyler, who says, "The child is naturally successively animal, anthropoid, half- barbarian, and then civilized."28 The other is taken from the literature of the "boy problem" which is fairly saturated with the doctrine. "We are by turns vertebrates, gill-breathing vertebrates, lung-breathing vertebrates (we make the great change at birth), little monkeys, little savages, and finally civilized men and women."29 It now becomes our object to examine briefly the facts of human infantile recapitulation. It will be impossible to cite every allusion of the kind, for these have been made casually in the course of numerous papers on an indefinite number of topics. The present intention is limited to a general charac- terization of classes of cases and to probabilities in the light of accepted principles of general genetic psychology. The degree of ignorance still prevailing with respect to the course of individu- al and racial psycho-genesis prohibits more than a preliminary survey of the topic. In making this survey of the facts we have the advantage of an hypothesis derived from the revision of the biological attitude toward the ancestral facts of embryology, as summarized in the preceding chapter, and illustrated further in the section on human embryogeny. What is true of embryogeny may be true of infancy. We may keep in mind the idea that the ancestral life-history has been transmitted from generation to generation as a whole, and that it has been altered with each step in descent rather than extended. In keeping with this view infancy prob- 2«Vol. II, p. 73. " See Thorndike, Original Nature of Man, 1913, pp. 249-252, for an Interesting collec- tion. 28 Growth and Education, 1907, p. 53. » Puffer, The Boy and his Gang, 1912, p. 77. Human Infancy and the Recapitulation Theory 81 ably has had its own evolution, having been evolved when it was needed, and having been altered from age to age from germi- nal mutation, and by selection as the necessities of its circumstan- ces required. We should expect to find in infancy a compara- tively small number of traits having an ancestral reference merely. These traits would be scattered and not related in a chronolog- ical sequence suggestive of phyletic recapitulation, and their ancestral reference would be first to ancestral infancies and only indirectly to adult characters for which the infantile condition was preparing. Some ancestral traits would perhaps have been made over in part to meet new conditions, and there would likely be an insignificant number of useless rudiments. The most important group of facts adduced in favor of mental recapitulation are those referring to a savage human condition, as illustrated in the behavior of lower living races of men.30 These include a large number of instinctive tendencies, especially among boys, which are characteristically savage. Some of these are the love of games embodying running, dodging, throwing, hitting with a club, wrestling, boxing; a strong interest in ad- venturous undertakings, fishing, swimming, exploits requiring endurance, courage, self-control, daring; outdoor interests in row- ing, sailing, climbing, exploring, the handling of animals, hunt- ing; the instinctive grouping in "gangs," group undertakings, hero-worship, group loyalty, antipathy for outsiders, fighting, with all its savage excesses, predatory excursions. The facts are too familiar to require further illustration. But this whole group of cases cannot be regarded as ancestral or in any sense recapitulatory; in fact it points quite the other way. The living races of men, to whose modes of life these examples all refer, belong to one species. The older view of Spencer, Galton, Fiske, and others, which held for an organic difference between savage and civilized human nature, has been supplanted by a conception of the essential identity in the hereditary make-up of all races regardless of the degree of civili- zation.31 The differences between civilized and savage men are chiefly, if not wholly, acquired and are due to the unlike exploitation of *> See Chamberlain, The Child, Chap. VIII, and Swift, Mind in the Making, Chap. II, for convenient summaries. 11 See Boas, Mind of Primitive Man; also, Thomas, Source Book for Social Origins. Part II, and bibliographies. 82 The Recapitulation Theory and Human Infancy human capacity by traditional and environmental forces. The savage character of boyhood is thus shown to be a necessary preparatory adaptation to the adult conditions prevailing at the period when human nature had assumed its specific form, conditions which are roughly pictured in the instinctive equip- ment of the boy whether the circumstances of his later life are still fairly true to the ancient pattern in some contemporaneous savage society, or whether they have been radically modified in the course of historical development. If this kind of boyhood in some respects seems out of place in civilization, it is not because it is rehearsing a former ancestral adult condition of life; it is due to the fact that the traditional and socially acquired habits have altered so much for the adult in some societies that what the boy is by nature disposed to do is not, superficially at least, just what is expected of him as an adult in these societies. Civili- zation has affected boys and adults probably equally. If this should not be admitted, and a greater resemblance be found among the young in different culture levels, this could very well be accounted for by the fact that the inhibition, selection, and organizing of the inborn qualities by habit and intelligence, have had less time to register their differentiating effects. This last thought may be used to explain another class of facts which has been supposed to illustrate recapitulation. Children are thought to betray ancestral limitations in their primitive tastes, their love of myth and of melodrama, of crude music, dancing, the spectacular, strong colors, etc., and on the side of conduct, in their laziness, desultoriness, dislike of work, discontinuity of attention, stealing, lying, truancy, teasing and bullying. But these things are not peculiar to children; they are found equally among uncultivated adults in civilized and uncivilized societies, and merely record the lack of cultural and moral discipline and the coercion of civilized industry. They manifest themselves wherever civilization is lacking, as in isolated or unfortunate classes in modern life, or in tramps or delinquents who for some reason have escaped its influence, and they are not unknown in cultivated adults when the tension of civilized habit is temporarily or suddenly removed. Continuing the process of elimination, we may refer to one other group of alleged recapitulatory facts. This includes cer- tain emotional attitudes associated with objects acting as their Human Infancy and the Recapitulation Theory 83 excitants. These may be illustrated by the fear of snakes and other animals, of celestial objects, of fire, darkness, eyes, teeth, solitude, death, disease, ghosts, etc. A very large number of similar attitudes have been cited as evidence of the recurrence in childhood of ancient attitudes which have been inherited. In all these cases there is evident a confusion of the inherited and the acquired. We are indebted to McDougall's "Introduc- tion to Social Psychology" (1908) for a lucid explanation of this matter. Each of the basic instinct-emotions has its charac- teristic "native excitants," with the inherent power of rendering it vital, or setting it up in psycho-physical behavior. Sensory abruptness, especially of sound, has this effect with fear; inter- ruption of normal functions is a similar excitant for anger; as is the infant wail for parental solicitude. The various native excitants have not as yet been satisfactorily described but the general principle seems clear enough. It follows that certain "objects" or acquired units of perception built around these excitants, will often have an emotion-exciting value because they so vividly contain the native excitants; such objects are thunder for fear or substances of vile odor for disgust. Other objects will have these emotion-exciting effects by association with the original ones, and it is apparent from the observed variety of these derived or acquired excitants that there is scarcely any limit to their multiplication. Almost every aspect of the natural world has been such a fear excitant, if we may believe the ethnol- ogists, and there is probably no conceivable object which may not have this function under appropriate suggestion. Only native excitants, then, can have ancestral reference, and we may safely neglect all objects connected with emotional attitudes and confine OUT attention to the possible recapitulatory value of «xcitants as such. Undoubtedly native excitants are very old, but as common experience testifies, they are not peculiar to infancy, and they cannot therefore be regarded as recapitulatory in this sense. It is not impossible that such native excitants may become so embedded in complexes with more dominant emotion-exciting excitants as to lose their original force. Such may be the case with aesthetic or religious objects containing essentially ugly or even essentially disgusting elements, but this does not of it- self assign the native excitant to infancy because it works there 84 The Recapitulation Theory and Human Infancy in simpler fashion. As to the excitants of attention, curiosity, and their derivative "interests," it is probable that the more conspicuous of these (such as sensory intensity, massiveness, visible motion), are common to children and adults. The strange-in-the-f amiliar as an incitement to attention and thought apparently affects both alike. Much of the "peculiarity" assigned to children's interest in natural phenomena and in the images of their minds can with practical certainty be assigned to the unlikeness in apperceiving content due to intellectual immaturity. The incitements to activity seem very closely related to children's capacities; when they find they are able to grasp they are interested in grasping, when they discover they can walk or climb, they take to these things with avidity, and so on through the succession of childish, youthful, and adolescent "activities." In these things childhood and youth are very obviously preparatory. Excitants are here nicely adjusted to disposing the young animal to undertake his own education the moment the underlying structures are ready. It is generally assumed that instinct represents the ancient basic structure upon which plasticity has supervened. A natural inference would identify the native excitant as the original cue to the unmodifiable action which preceded the plastic or habit- induced action in the phylogeny. This is of course not necessari- ly the case, for the original cue may have altered in descent along with the supervening plasticity, in accordance with the theory of organic selection. However, it is at least likely that the native excitant is a conservative and comparatively ancient feature of psycho-physical organization, even if it has not remained wholly unchanged. If this is so, the progression in the infant from the native excitant to the "meaning" which absorbs it, is homologous with the original phyletic progression from the ancient sensori-motor to the percept-motor action system, and we are apparently confronted with a genuine case of ontogenetic rehearsal or "recapitulation." If now we turn to the motor aspect of the presumably ancient instinctive structure we find the distinction, commonly assumed, between its inherited and involuntary expressions and the ac- quired habits which grow up with use and exercise. But the case here is not the same as with excitants and meanings. Plasticity presumably has not been merely added to instinctive muscular Human Infancy and the Recapitulation Theory 85 action; it has reduced it, permeated it, and substituted for it; that is, essentially altered it rather than supplemented it. As Lankester puts it, plasticity can rise only as instinct yields it place. It is customary, therefore, to speak of the involuntary instinctive motor expressions, — those discussed by Darwin and other students of the emotions — as remnants of older and more complete action systems. With what degree of justice this assumption is made is a question, for the evolution of skill is a comparatively neglected topic. Students of the animals have thus far been chiefly concerned with the problems relating to animal intelligence. Still, there is probably no counterpart to the genetic sequence from native excitant to meaning on the side of motor control. In fact the situation seems just reversed. For phylogenetically there was a progression from stereotyped behavior to less and less fixed modes of behavior. Ontogenetically the progression is from a few established modes to an indefinite number of adapted voluntary habits. And these acquired habits cannot be homol- ogous with the instinctive phylogenetic action systems, for the very good reason that motor plasticity was evolved for the express purpose of substituting better and different action systems for them. There is, however, the possibility that there may be examples of recapitulation among the various types of inherited modes of movement: the automatic visceral control, the involuntary accompaniments of the emotions, (fear, joy, grief, "expression")* the random movements of early infancy, and the true reflexes. With respect to the first two, so far as the writer is aware, there are no essential differences between youth and maturity excep- ting such as are induced by habit with the second, and none that requires an ancestral explanation. Mumford3* advanced the theory that the random movements of early infancy, associated with the gradual ripening of the lower centers, are reminiscent in certain cases of ancient aquatic modes of action. The suggestion is perhaps a possible one without being at all convincing, and surely the resemblance is not conspicuous. Besides, as Miss Shinn notes, in commenting on the suggestion, many of the movements such as the asymmetrical movements of the eyes, » Brain, Vol. XX, 1897. 86 The Recapitulation Theory and Human Infancy grimacing, the rolling of the head, cannot be brought under the theory at all.33 The sucking and crying reflexes of the infant are obviously adaptations. As for sneezing, yawning, coughing, and similar reflexes, all these appear early and remain essentially unchanged through life. Certain other reflexes and a number of physical traits, were collected by Robinson,34 and Buckman,36 and offered as illustrations of recapitulation. Examples of infantile adaptive characteristics from these writers referring to the pithecoid infantile condition are the clasping reflex, the supporting of the body by the hands and arms, the thumb -like action of the big- toe — all having to do with the necessity of holding fast to the hair of the mother in arboreal life. The very early "hide and seek" propensity of babies is another example of pithecoid recapitulation. Examples of physical traits are the baby's snub nose, prognathism, remnant of lip furrow, tail mark, long arms, position of the legs and feet, and the plantar lines. If one should be disposed to grant a certain plausibility to these cases of ancestral reference, there is still no necessity of assigning them to the adult monkey or ape, where they are not obviously infantile. They may very well resemble the adult because of the infant ape's resemblance to its own adult condition and they thus become illustrative of ancestral ontogenetic resemblance. They may be compared with the many pithecoid vestiges remain- ing in the human adult organization, and before any assertion of greater antiquity of infancy as such can be made it is necessary to show that they are representative of a very much larger group of such vestiges than can be found in adults. This is to say, the whole human ontogeny has pithecoid vestiges. Of course infancy has its share. Other illustrations of recapitulation from the same source are referred to the conditions of primitive man. The intensity of fear in children, useless crying, shyness, the instinctive appeal and clinging to the parent in the presence of strangers, — these recall the dangers of the early life of man. The greediness and selfishness of children point to a considerable degree of parental neglect and a consequent survival of those who managed to fend " Notes on the Development of a Child, Vol. I, p. 397, footnote. "Nineteenth Century, Vol. 30, 1891; Vol. 31, 1892; North Amer. Rev., Vol. 159, 1894; Brit. Med. Journ., Vol. 2, 1891. « Nineteenth Century, Vol. 36, 1894. Human Infancy and the Recapitulation Theory 87 for themselves. The plumpness of babies as a precaution against famine, infantile attractiveness as an evidence of primitive paren- tal selection, the strong interest in animals, the carrying of things to the mouth, and many other childish characteristics are given their appropriate recapitulatory explanation. The value of this type of evidence will doubtless vary with the sense of credulity, but, accepting them at their face value, it is to be noted that some of these traits may still be of value to the species in existing savage societies, others refer to infantile adaptations in the past and not to remote recapitulations, and once more illustrate the familiar principle of ancestral ontogenetic resemblance. Infants today resemble the infancies of their ancestors just as adults today resemble ancestral adults. As for emotional equipment, children and youth have no characteristic attitudes of the kind which are inaccessible to the sympathetic appreciation of adults. Like native excitants their early character may be simpler, but they are not different in quality. The one attitude, which by reason of its oddity for adults has been designated a "mania," is that of collecting.36 One has difficulty in seeing a preparatory value in this propensity. Perhaps it had an adaptive value in earlier infancies. Seemingly fear is intensified with young children, and it may be the egoistic sentiments are more powerful relatively throughout the earlier part of immaturity. It has been noticed that Robinson saw in these things illustrations of infantile adaptation. The two great sources of altruism are more especially associated with advanced stages of development, — friendship with the clannish- ness and romantic love of the pubertal and adolescent years, parental regard with the coming of offspring. Childhood, although not devoid of these sentiments, does not need them in the same way. Its major business is to practice its own individual powers.37 Drummond,38 following Romanes, asserted categorically that the order of the appearance of the emotions in growth is the order of their distribution on the scale of animals. As to this 16 Thorndike finds abundant evidence of this instinct among adults, op. cit., p. 267. 27 For a pungent criticism of the recapitulation theory as applied to mental genesis, together with a clear statement of the "utility" theory, of which he is an advocate, see Thorndike, op. tit., chapter XVI. For an earlier statement of this latter theory, aee King, Psychology of Child Development, 1904. w Ascent of Man, p. 133. 88 The Recapitulation Theory and Human Infancy it must be said that the lack of knowledge of the probable facts in either series prohibits inferences.89 Grouping together the less propulsive and more passive in- herited psycho-physical traits under the head of "sensibilities," it is to be noted that President Hall and others have called atten- tion to possible recapitulations in this region. Certain hedonic qualities attached to sensations of touch, smell, and taste, especially, are thought to require an ancestral explanation, one reason for this being the probable degeneration of these senses and their old-time greater importance. This is not an unreasonable attitude, for the protection afforded by the evolv- ing higher senses might well permit the carrying down of useless remnants of the kind. Instincts, intelligence, and modes of action under the guidance of sight and hearing, would doubtless be more directly subject to natural selection. There is, however, a lack of convincing evidence of any predominance of such traits with the young as such, and until this is forthcoming there is no need of appealing to recapitulation for an interpretation of such cases as may seem truly vestigial to adults. Baldwin's acceptance of recapitulation was due in part to his belief in its unimpaired standing in biology as late as 1906, to the idea that it was logically required as an effect of heredity, and to the parallel he found between the great epochs of psycho- physical evolution in the race and comparable epochs in individual mental development.411 It is true Baldwin noticed very signi- ficant departures from a faithful psycho-physical recapitulation, some of which have been referred to in the present discussion. Indeed they might well seem to his reader much more impressive than the arguments he adduced in support of the theory. Bald- win's first two reasons for a modified acceptance of recapitula- tion have been sufficiently discussed. Without following his analysis in detail we may consider briefly his empirical support of the theory in terms of current ideas of psycho-physical evolu- tion and development. The students of comparative psychology have agreed fairly well upon the main outlines in the evolution of behavior. The series of epochs in this evolution is represented as follows : The period of the tropisms ; that of the reflex and the essentially unmodifiable instinctive behavior; that of very grad- »• Compare Thorndlke, op. cit., p. 256. *• Mental Development, Chap. I. Development and Evolution, Chap. I. Human Infancy and the Recapitulation Theory 89 ually modified instinctive behavior; that of intelligence, or the more abrupt adjustment of instinctive modes to the perception of related "objects," with its associated revival and desire; that of the imitative and lower types of conceptual intelligence of the primates; and finally the rational learning of man.41 These are of course not distinct^ marked periods but rather points of emphasis in a gradually changing evolution. To what extent is the series paralleled by the development of the human individ- ual? It is wholly beyond the scope of the present discussion to make a careful study of the correspondence. One can here speak of probabilities only, in view especially of our ignorance of the course of individual development. The underlying organic structures are of course wholly incomparable. They are as unlike as the complicated human nervous system at birth and undifferentiated protoplasm, to refer to the two extremes; or as the infant human and pithecoid brain, to narrow the interval of contrast. The point at issue is whether the rise of psycho- physical functions in the human child follows in an homologous fashion the course marked out by the evolution of behavior. The nervous control of human behavior offers no ground of comparison with the tropisms. With regard to the reflexes of infancy, it is obviously impossible to establish genuine homologies with the lowest animal reflex action systems. In their origin they were undoubtedly removed from primordial phylogenetic systems by inconceivable intervals of time, and their only common attribute is their reflex quality. Moreover, they do not consti- tute an "epoch" in development, in the sense that they are succeeded by a later and different mode or organization, for they persist throughout life. The random movements do sub- side and give way to higher systems, but even if these be regarded as peculiarly ancestral, they are so only as fragments of older more complete instinctive systems and not as representative ancient reflexes. Again, it is not at all obvious that the particu- lar reflexes that remain in man are especially old in comparison with his instinctive make-up. The sucking reflex has risen with the mammals; it is probably much younger than the basic fear structure. What is true of this reflex may be true of others. 41 See Hobhouse, Mind in Evolution, 1901 ; Morgan, Animal Behavior, 2nd. ed. 1908; Holmes, The Evolution of Animal Intelligence, 1911. 90 The Recapitulation Theory and Human Infancy Similarly the instincts do not constitute an epoch in human development for they also rise early and persist through life, speaking generally. But we have noted that the progression from the native excitant to "meaning" seems to represent a phylogenetic rehearsal, and we are confronted by the very signi- ficant fact that the sequence from assimilative through intelligent to conceptual learning is one that has been illustrated in the accounts of the evolution of intelligence indifferently from the animal series and the course of the child's intellectual progress. Romanes, for instance, believed implicitly in the closest possible correspondence of animal and childish modes of thought, up to the point where human intelligence passes beyond the limit of animal capacity.42 And this assumption of a fundamental likeness of childish to animal modes of learning is not confined to older accounts but passes as a sort of commonplace in current discussions of intelligence. It has been very generally held since Romanes that the differences in intelligence whether ex- hibited in animals, primitive men, or children are differences not in kind but in degree, and there is undoubtedly implicit in these views the thought that there exists some kind of scale or genetic progression against which all acts of intelligence may be measured. It has, in fact, been assumed, whether properly or not, that intelligence in its representative character cannot differ in kind but only in degree. For intelligence has been regarded as yielding a direct acquaintance with the environing world, so that a better acquaintance with this world could only mean a more adequate relationship of the same kind. If, then, lower animals have any intelligence they must possess some amount of the same thing which higher animals and human beings possess in larger measure.43 The progressive character of the "Mental Evolution in Man, passim. 43 That its a priori attractiveness has favored this assumption is probably true. An adequate treatment of it in the light of the available facts is beyond the possi- bilities of this account. Yet a few obvious considerations may be noted. The low type of learning involved hi the dropping of useless movement or in threading a maze may be effective without being representative, and so escape the implication of the assumption in question. The possession of a free prehensile organ has been noted as of first importance in the perception of objects and their qualities, and as a probable source of difference between human or pithecoid and lower animal intelligence (com- pare Washburn, Animal Mind, p. 279). And the contribution of the linguistic func- tion to intelligence must be remarked, whatever this is. That much remains to be said for the view here referred to, despite such considerations, is apparent. See, for instance, Morgan, Animal Behavior, pp. 332 et seg. Human Infancy and the Recapitulation Theory 91 evolution of intelligence has derived added support from the views currently held of the historical increase in complication of the nervous system, especially of the cerebral portions. The original segmental nervous system has been successively inte- grated, first by co-ordinating centers of limited scope, and suc- cessively by hierarchies of increasing range and inclusiveness. This evolution has been in the main one of gradual progression in a given direction, and those portions associated with intelli- gence are regarded as being peculiarly illustrative of this order. In a passage in which he characterizes the method of his work on the evolution of mind Hobhouse speaks somewhat explicitly of the homologies existing between human and animal modes of intelligence. Referring to the stages in mental evolution as summarized in Chapter XV of his book, this writer says, "The fourfold method of correlation differing stage by stage (a) in respect of the factors explicitly taken into account, and (b) therewith in extent of the sphere comprehended, appears to the writer to be realized in human consciousness as we run the gamut from philosophical reflection down to the quasi-mechan- ical response of habit. Whether these stages into which de- veloped human reason can be analysed correspond to stages by which it grew is of course another question — a question only to be answered by a much wider knowledge of animal psychology and of the distinct processes of human development than we at present possess. If we accept evolution, analogy suggests that human intelligence is a specific and higher development of a more general form of intelligence. Hence, if we cut away the higher development, we should come to something roughly common to man and the higher animals. If we cut further, we should come to something common to man and a wider class of animals, and so forth. But there is a caution to be borne in mind. No two species will come to a quite identical development. No part of the physical structure of man, I suppose, is precisely equivalent to the homologous part in another mammal, still less in another vertebrate of a different class. It is the same with the mental structure. We must not expect to find any animals whose intelligence falls readily into any classification based on the analysis of human experience. We can only expect to find homologous developments. That being understood, it may be said that the method of the preced- ing chapters, so far as they relate to animals, has been to analyze out the phases of intellectual development as distinguishable in human experience, and to discover what homologous structures 92 The Recapitulation Theory and Human Infancy are to be found in the animal world. In accordance with these homologies animals are ranked in the classification.44 Hobhouse here again gives expression to the pervasive idea that has played so large a part in all ontogenetic study, namely, that the theory of evolution implies a progressive historical sequence that becomes registered in development. We now know that this is not the only method in evolution. Rather, if the evidence presented in the first chapter is representative, it is the unusual one, the life history being so altered in the suc- cessive stages in descent as to leave comparatively few evidences in any one ontogeny of what took place in the phylogeny. But it may be that in the case of intelligence there has been just such a progression. The theoretical considerations to which reference has just been made, and the degree of success which has attended the work of students of mental evolution who have assumed it, give a fair presumption of its actuality. The prin- ciple of homologous relationships obtaining between animal and childish modes of thought therefore remains as a valid working hypothesis, and recapitulation may reasonably be ex- pected to find illustration in this direction. What we already know of the correspondence, however, forbids the acceptance of Romanes' belief in a close similarity. It may be, for instance, that the phylogenetic order is not so much shown through chronological periods of immaturity as in the progression from ignorance to conceptual or rational control at any period of growth. And there is the further possibility that intelligence has been adapted not only to human interests as contrasted with animal interests — which is obviously the case — but to par- ticular phases of psycho-physical organization, as in connection with the development of skilled voluntary movements. As Hobhouse suggests, we are not yet in a position to speak with any confidence of the real character of the correspondence, if it exists. This survey of the facts offered in behalf of psycho-physical recapitulation is far from complete, but the more prominent illustrations have been referred to, and they probably warrant tentative conclusions. On examination the more striking cases are found to refer not to ancestral savage conditions, but to « Mind in Evolution, p. 327, footnote. Human Infancy and the Recapitulation Theory 93 treits characteristic of the human species in general which have been differently affected by the contingencies of historical development. The civilized societies work differently with the same human nature and by contrast the fundamental inborn traits seem ancestral when they are only less trained. Other cases rest upon analogies due to a confusion of inborn and ac- quired elements in mental organization. Assertions of a phylo- genetic rehearsal in the order of appearance of traits have been made without empirical warrant. In the interests and activi- ties which more especially characterize development as such, the preparatory nature of immaturity is obvious, and this is well illustrated in the group of cases which have had greatest emphasis in connection with mental recapitulation. In the matter of intelligence certain general considerations, as well as' a considerable amount of inductive study, give a fair presumption of some degree of ontogenetic-phylogenetic correspondence in this region. 4- Cultural Recapitulation. Cultural recapitulation, or the theory of culture epochs, has had a curious status in educational literature. While its sep- arate origin has been acknowledged, and its integrity as a sub- ject of discourse has been maintained by an independent title, as a matter of practise the discussion of biological recapitula- tion has encroached upon its territory with impunity and ap- parently without full knowledge of what it was doing. For it is clear that any application of biological recapitulation to men- tal development as a whole deals directly with the question of how its cultural acquisitions are assumed, whether in the order followed by the race in the historical development of its cultural products, or in some other way. And it is a commonplace of the literature of recapitulation based upon the biological analogy that the transition from barbarism to civilization con- cludes the phylogenetic sequence. Now the doctrine of biological recapitulation had reference to ancestral species. By the statement that ontogeny re- hearses phylogeny was meant that ontogeny repeats the suc- cession of steps in the biological evolution of ancestors. This was due to the force of heredity operating in descent despite the modifications which marked the successive stages. But the transition from primitive to civilized man, according to pre- 94 The Recapitulation Theory and Human Infancy vailing views, is not a biological progression. Primitive man and civilized man represent the same species and the same men- tality. The differences between the two are due in the main to the unlike use of this common mentality by social and environ- mental forces. Therefore historical development is not phylo- genetic, but ontogenetic, i. e., has taken place in individuals of the same species. Biological recapitulation applied to the mind of man must be held to refer to the alleged correspondence of the hereditary sequence of psycho-physical functions in indi- vidual development with the succession of homologous func- tions in the series of ancestors. It applies then to the appear- ance of reflexes and instincts, and to psycho-physical modes; only indirectly to habits or acquired products represented in culture. Our treatment of these matters has just been con- cluded in the preceding section. We address ourselves at pre- sent to the somewhat distinct issue of cultural recapitulation. There is no need of recounting the history of the theory of cultural recapitulation here. This has been done elsewhere.45 The general bearing of the present discussion upon the theory may, however, be briefly indicated. Cultural recapitulation rests upon three distinct propositions: 1. The historical develop- ment of culture, either as a whole or in particular lines, was determined in some degree by the inherent nature of the human mind which permitted this order and no other. 2. There is an inherent and necessary order in the acquisition of culture by the immature mind. 3. The underlying necessity in develop- ment is identical in the two series. Let us consider the status of each proposition. 1. The con- ception of an inevitable order in the development of culture was apparently a derivative and special application of the idea of biological evolution to social phenomena when the prestige of the new doctrine was very great and when the sciences of anthropology and sociology were yet in their early stages. The application is due chiefly to Spencer, Tylor, and L. H. Morgan.46 The empirical basis of the conception consisted of similarities which were at first found conspicuous among all races, and more especially of parallel lines of development in culture which were « Vincent, Social Mind and Education, 1897, Chap. Ill and IV; Dowey, art. Culture Epochs Theory, in Monroe's Cyclopedia of Education. See also, Henderson, Princi- ciplos of Education, 1910, Chap. VI. « Boas, Mind of Primitive Man, Chap. VII. Human Infancy and the Recapitulation Theory 95 considered general. Later investigation and discussion seems to have sadly shaken the foundations of the conception. It has been pointed out that similarities may be due to factors other than common mentality, such as similar geographical environ- ments, common points of radiation of culture, common tradi- tions, and convergence from unlike sources of origin. Investi- gation has dealt even more seriously with parallels in develop- ment. The words of two anthropologists writing with high authority will suggest the present situation in the science with respect to the conceptions in question. "The theory of parallel development, if it is to have any sig- nificance, would require that among all branches of mankind the steps of invention should be followed, at least approximately, in the same order, and that no important gaps should be found. The facts, so far as known at the present time, are entirely contrary to this view. We are thus led to the conclusion that the assumption of a uniform development of culture among all the different races of man and among all tribal units is true in a limited sense only."47 The different races cannot be arranged, therefore, on a scale of culture. "While parallelisms of a certain kind were shown [by the older students] to occur, this does not hold for parallelisms of any degree of complexity and duration, nor for integral historic processes, the individuality of which seems so conspicuous that doubt prevails in the highest quarters as to whether anything like historic laws in the strict sense will ever become more than a desideratum." "Whether the parallelisms refer to entire historical complexes and embrace millenniums, or modestly comprise parallel develop- ments of less extent and duration, when demonstrated they do not constitute a solution, but a problem which has not so far been successfully attacked."48 It will be noticed that these writers do not wholly repudiate parallelisms in development due presumabty to common men- tality. Their expressions have the force of setting positive limits to the idea of their general prevalence held by the older anthropologists. They also may not do justice to the fact that there exists in then- science an element or school laying great stress upon the factor of common mind. Wundt's "Volker- « Boas, op. «'«., pp. 182, 195. a Goldenweiser, Jour, of Amer. Folklore, July-Sept., 1913, pp. 281, 283. See also, Boas, in Thomas, Source Book of Social Origins, 313-15. 96 The Recapitulation Theory and Human Infancy psychologie" represents the farthest advance in this direction, and while this work is regarded as having the imperfections of a pioneer effort, promise in this type of anthropological study is not denied. As a matter of fact the sciences of anthropology and psychology have not as yet been vitally joined in the in- vestigation of culture, a significant thing in itself for our topic. For the present it must be admitted that the idea of a neces- sary order in historical development of an inclusive sort is some- what under suspicion. The possibility, or rather the actual existence of isolated cases of cultural parallels, seems to be generally acknowledged.49 2. Passing to the second proposition contained in the theory of cultural recapitulation we find an equally uncertain situation. That there is a determined order in some part of the progressive development of the child mind no one doubts, and serious ef- forts have been made with a view to its description. But it cannot justly be held that a description of this order in general terms has as yet been agreed upon by the students of child psy- chology. More especially, the distinction necessary to an ap- plication of the culture-epochs theory, between deferred inborn or original traits and those traits which are to be regarded as the results of exercise and cultural stimulation, has not yet been determined with clearness, and until this distinction is made it is obviously impossible to institute comparisons between racial modes of cultural acquirement and genetic sequences characteristic of the learning of children. Speaking broadly, the many existing characterizations of "periods of development," of "interests," or of "nascencies," etc., besides being too various for general acceptance, deal indifferently with the appearance of original traits and the development of acquisitions. Valu- able special studies in certain lines are not wanting, notably in language and drawing. Recently, in connection with mental testing, progress towards maturity has been measured, but as yet a qualitative description of this progress has not been under- taken. On the whole, there is no question of genetic sequences in many aspects of mental and cultural growth. We are, how- ever, still in the dark as to just how these sequences should be systematically described. « A philosophical and critical survey of the histoiy of human progress conceived largely in genetic terms is that of Santayana's Life of Reason (5 Vols., 1906). Human Infancy and the Recapitulation Theory 97 3. Notwithstanding the insecurity of the two primary as- sumptions underlying the theory of culture-epochs, the develop- ment of the individual and that of the race have been found by serious students to have much in common.50 A competent examination of any one of the many applications of the theory of cultural recapitulation is beyond the scope of this paper. They range from religion to mathematics, and call in each case for very special knowledge of the history of the branches of culture in question, as well as for a broad equipment in the psychology of the mental processes implicated. We can deal here with but a few logical considerations. It would not be surprising if the theory held that mature men in a given society were required by their inherent nature to follow in some degree the development of the culture that had been evolved by mature minds in the course of history, for this would imply, apart from the differentiating effects of environ- mental influences, only some common mentality among adults in the same species and some common elements in their modes of progression in any given cultural direction. We have already noticed the difference of opinion between the anthropologists and psychologists with reference to this possibility. But the theory goes beyond this. It asserts that unlike ontogenetic periods may be compared with respect to their cultural acquisitions. The child's mind is said to rehearse the history of culture, which is essentially the expression of matur- ity. Supposing, then, that a true genetic sequence had been determined in the historical development of a given branch of culture, based upon parallels among the different races of men, is there a possible warrant for the assumption, made in the culture-epochs theory, that a child's progress in this branch of culture may be so accelerated that he can accomplish in his immaturity what adults in the past could with difficulty attain to? The answer to the question could be determined of course only by an appeal to fact, but such acceleration is not impos- sible if certain conditions be assumed. If the underlying or- ganic basis for the historic progression has always been the possession of childhood, and the conditions in civilized societies « See the account and references of Vincent, toe. cit., also Ribot, Evolution of General Ideas, 1899: Branford, A Study of Mathematical Education, 1908; Huey, Psychology of Pedagogy of Reading, 1910, Part II.; Baldwin, Thought and Things. Genetic Logic, 1906. 98 The Recapitulation Theory and Human Infancy are now especially favorable to its functioning, it need not be surprising if children should exhibit achievements that were characteristic of adult societies in past times. For adults in these societies were, on the present assumption, in a state of arrest. From childhood they had had the capacity for advanc- ing beyond the point of their actual adult attainments, but their advance was prevented by the limitations of their cultural environment. To illustrate, if in a genetic sequence symbolized by the series a, b, c, d, e, f, childhood or youth has the inherent capacity for rising to stage d, and does so in the highly favor- able environment of civilized societies, it is easily conceivable that adults in historical times, laboriously evolving their culture independently, should remain life-long at points b or c. This is no more than the equivalent of the thought that primitive and historical men were relatively childlike, a familiar and wide- spread idea among students of early cultural expressions. From this it would follow that cultural recapitulation need not be expected in any regions where organic differences between children and adults exist. If certain branches of culture are expressive of characteristically adolescent or mature attitudes it will be idle to search for illustrations of their genetic rehearsal in earlier periods. And since cultural recapitulation has to do with acquisitions and processes of acquiring we must limit our search for such recapitulations to the course of development taken after the basic instinctive structures have begun their functioning, at whatever period of growth this may be. It is perhaps not possible as yet to characterize the disting- uishable lines of growth within the complex field of cultural acquisition. They are broadly represented by taste, moral and social character, motor skill, and ideas, but these obviously overlap. An adequate analysis of the general principles of mental development will doubtless deal with much finer cate- gories. It is worthy of notice that those who have done most with the cultural recapitulation hypothesis have worked more particularly in the field of thought and it is not impossible that reasons may be found for regarding the plasticity represented by thought and ideas as being available so early in life as to make possible a genuine comparison of childish and historical pro- cesses. And since ideas are most intimately related with every aspect of cultural acquisition the possibility may be extended in some degree to motor, moral, and aesthetic development. CHAPTER IV CONCLUSION The history of recapitulation is an instructive one. A prin- ciple of limited application within the field of its origin was elevated to a position of wide generality, and so gave rise to a conception in the main misleading. Carried into a new terri- tory without a sufficient examination of its merits, it was ap- plied broadly as an explanatory principle and thus distributed its misleading influence beyond its own borders. Disregarding the qualifications which were forced upon it by recalcitrant facts, the conception represented a view of individual development as successively extended in the course of evolu- tion, in such fashion that in any ontogeny the earliest features are oldest, the later ones in succession increasingly recent. Thus embryogeny as a period was oldest, infancy less old, and matur- ity the last to evolve. From this form the conception degener- ated to a less and less chronological notion, until it came to mean often no more than that any particular feature in development which had an historical rather than a present reference was illustrative of it. A more thorough consideration of the facts has led to a view of development essentially contradictory of this recapitulatory one. Ontogeny represents the ancient life-cycle which as such has been transmitted from the beginning. The chronological sequence from egg to maturity is not a rehearsal of a like his- torical series of events throughout the phylogeny of species; it is but the recurrence of an order which has been repeated in the lifetime of each individual from the beginning. In general, the effect of the modifications induced by germinal mutations and selection in the successive ontogenies constituting the phj'lo- geny, was to alter these ontogenies, to make them over, and to destroy the resemblance of later ones to their predecessors. Still this alteration was not complete; neither was it regular in its effects. Some very ancient forms are still hinted at in 99 100 The Recapitulation Theory and Human Infancy existing ontogenies; more especially particular structures were often retained through long periods of time with considerable faithfulness. Because of the slowness with which modifications occurred, any ontogeny repeats most of the features of its proxi- mate ancestral ontogeny, and in general the record grows less and less true of phyletic ontogenies with remoteness in descent. Because any ontogeny thus throws some light upon earlier ones, and particularly upon proximate ones, the facts of ontogeny gathered together help to reconstruct the whole line of descent. Probably this is what is often meant by the statement that on- togeny is a record of phylogeny. The statement should read that genetically related ontogenies when compared supply some ground for reconstructing phylogenies. Although the effect of mutation and selection was in general productive of alteration of the life-cycle, evidence points to a considerable amount of extension of the life-cycle coincidentally with alteration. This happened at times with the form of the organism as a whole, but more often with particular organs or structures. These considerations apply to the period of infancy with qualification. Infancy was evolved from an ancient life-cycle which did not possess such a period, presumably during and since the Age of Mammals. We can only guess as to the nature of its origin. It may represent a modified later part of the ancient embryogeny set over into the post-natal period, or it may be a remodelled part of the ancient period of precocious maturity, or it may be both. In any case it is probably not due to the successive extension of the mature end of old ontogenies, and there is no need presupposing evidence within it of such extensions. It is, rather, probably the ancient structure of maturity, either in process of growth or in completion, shorn of and supple- mented by those things which plasticity presupposes. In its most ancient features, such as the emotional phases and involun- tary rudiments of instinct, it probably retains the characteristics of maturity. We have seen no reason for assigning differences between human infancy and adulthood in these respects. As for the rest, we may tentatively bring over the classification of features employed by Duckworth in connection with human embryogeny, as follows: Conclusion 101 The infantile condition as such explains many adjustments that natural selection might have insisted upon — the earl}' dependence, both physical and mental, upon the mother; the later larger degree of self-care and self-protection, through fearfulness, shy- ness, greediness, and selfishness. Then there is the necessity of preparing for the adult condition — the spontaneous interest in self-practice, the close correlation of mental need and maturing structure as exhibited in the succession of interests, followed by the palpably preparatory conditions of puberty and adolescence. 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