The Play of Animals
Chapter 2: Play and Instinct
WOULD it not be building on water or shifting sand to attempt the explanation of a psychological phenomenon by means of the mere concept of instinct? " The word instinct," remarked Hermann Samuel Reimarus in 1760, " has been until now so vague and unsettled that it scarcely had any certain meaning, or rather it had the most various uses." This was still quite true up to the middle of the present century of the topic as a whole, and it will probably always continue to be true in regard to many details. " In speaking on instinct," says Ribot, with laconic brevity, " the first difficulty is to define it." Since the time of Darwin, however, a great and important forward step has been taken, and Darwinism has assumed of late years a form that offers a fixed point of departure for the investigation of the problem that concerns us in this chapter. It is by no means my intention in what follows to give a history of the idea of instinct- a task never yet undertaken, to my knowledge. Still, it is necessary to clear the way for the comprehension of the problem and the appreciation of the view which I shall advocate, by
(26) a glance at the most important positions of modern thought. The following points of view may be distinguished:
1. The transcendental-teleological conception: (a) the theological, (b) the metaphysical, explanation of instinct.
2. The point of view which repudiates the notion of instinct.
3. The Darwinian solution, by means of (a) the transmission of both acquired and congenital characters; (b) the transmission of acquired characters only; (c) the transmission of congenital characters only.
Very early in modern thought we see the theological form of the transcendental-teleological conception of instinct brought forward by Descartes. For while he, following the Spaniard Pereira, denied to animals a reasoning intelligence, and considered them as mere machines or automata, he advocated the idea that the apparent intelligent actions of animals are to be traced directly to divine influence. The almost marvellous suiting of means to end seen in the actions of many animals, especially those displaying constructive instincts, furnishes sufficient ground for a similar opinion among many not at all inclined to deny all intellectual life to animals. (The strict Cartesian doctrine was for a long time so influential that the celebrated Leroy, through fear of persecution by the Sorbonne, published his letters on animal intelligence  as the work of a "physician of Nuremberg.")
The idea that these mysterious instinctive capabilities are directly implanted in the animal by God had a
(27) great attractive power for religious natures, and especially so at the epoch of the Enlightenment, that period of reflective thought when the favourite attitude was one of " adoring contemplation " of the Creator's power. A naive conception of the universe like that of Gellert, for instance, who informs us in one of his poems that God called the sun and moon into existence for the purpose of dividing the seasons, naturally impels its holders to similar conclusions with regard to the adaptation of animal instincts. Two examples from this period and three modern ones may serve to illustrate this conception. Romanes quotes this remark of Addison's: "I look upon instinct as upon the principle of gravitation in bodies, which is not to be explained by any known qualities inherent in the bodies themselves, nor from any laws of mechanism, but as an immediate impression from the first mover and divine energy acting in the creatures."
Reimarus regards instinct as a direct proof of the existence of God. His work, referred to above, contains a chapter on knowledge of the Creator through animal art--impulses, in which he expresses the opinion that such powers of body and soul as animal instincts disclose surpass the forces of Nature, showing us the " wise and good Author of Nature who has appointed for every animal the powers necessary for his life."
A definition from the eighth edition of the Encyclopaedia Britannica may be mentioned as a modern example:  "It thus remains for us to regard instinct as a mental faculty, sui generis, the gift of God to the lower animals, that man in his own person and by them might be relieved from the meanest drudgery of Nature."
Brehm mentions a professor of zoölogy by whom the old theory of instinct was set forth in its crude dualistic form- which was at that time combated most energetically by the opposers of the word instinct- i. e., that animals have only instinct and; no reasoning powers, while man has reasoning powers and no instinct. " We know well," says this zoölogist, " that a being capable of adapting means to his ends must be a reflecting, reasoning being, and that in this world man is the only such being. An animal does not think, does not reason, nor set itself aims, and therefore, if it acts intelligently, some other being must have thought for it. A higher law provides the ways and means of its defence. The acts of men alone are governed by their own reason. Deep thought is doubtless disclosed in the actions of animals, but the animals did not think them any more than does a machine whose work represents an embodied chain of reasoning. The bird sings entirely without his own cooperation; he must sing when the time comes, and he can not do otherwise, nor can he sing at any other time. The bird fights because fight he must by order of a higher power. The fact is evident that the animal does not consciously fight for any special thing, such as the undisturbed possession of the female, nor seek by his struggles and effort to attain it. He acts as a mere creature of Nature under her stringent laws. It is not the animal that acts, for he is impelled by a higher power to altogether fixed courses of conduct. Parent birds can not deviate from a certain fixed method of rearing their young; both must work and help in the process; a command from above compels them to stay and work
(29) together. This is all that a happy marriage means to birds. There is no freedom, no voluntary action, no play of varying moods, no life of emotion or of thought to be expressed in the animal's actions. Without knowing what he does or why he does it, he makes directly for Nature's goal."
The well-known zoölogist Wasman refers instinct to the Supreme Power, but with greater moderation. He holds that in instinctive acts themselves feeling and presentation may be present, but, so far as instincts are not explicable by the animal's own intelligence, he refers them to the Creator's influence. " Since," he says, "animals do not know the end of their instinctive actions, so much the less can they consciously pursue it. There must be a higher intelligence present, which not only knows the end but has ordered it. This intelligence can be no other than that of the Creator who has arranged the order of Nature, and made everything conducive to the proper preservation of that order. The adaptability of the several instincts of unreflecting brutes, as well as their correlation to those of other members of creation, must have its origin in creative intelligence."
The efforts of metaphysicians to find a solution of the question are of a similar character. The spiritual principle is, of course, substituted for the Christian's God, but the transcendental-teleological view is retained. A few citations may be useful here too. Schel-
(30) ling puts All-pervading Reason in the place of a personal God. " Animals," he says, " in their acts express or witness to the All-pervading Reason, without themselves reasoning. Reason is in what they do without being in themselves. They may be said to reason through the force of Nature, for Nature is reason." And likening instinct to gravity, as Addison did, he reaches the conclusion that " the animal is held by instinct to the absolute Substance as to the ground by gravitation."
G. F. Schuberth derives instinct from the " worldsoul."  K. C. Carus says it is " the unconscious working of the Idea " that produces organic adaptation and beauty, and also instinctive activity. Similar to this is E. von Hartmann's tracing of instinct to the " Unconscious." An exact student of Darwinian literature, he recognises the Darwinian principles only as means or instruments used by the Unconscious, in which alone the ultimate explanation is to be sought.
So much for the transcendental-teleological theory. I am far from concurring with the many modern investigators who regard all religious or metaphysical ideas with contempt, seeing in the former a disease of youth, and in the latter youthful sentimentalism not worthy of the serious consideration of riper years. In a dec-
(31) -ade when we again stand at a turning point of time, when in polite literature the word is, Naturalism is dead; when plastic art turns toward a manifold, mystic, new idealism; when a Neo-vitalism is arising in biology; when a Brunetière proclaims with cool audacity the bankruptcy of positive science --such a time is hardly a suitable one for the too confident assertion of the all-sufficiency of the exact sciences. Weismann has indeed given the title " The All-sufficiency of Natural Selection " to one of his essays, but in another of his writings occurs a figure which I like better. In contrast to the common opinion which likens empirical knowledge to a building resting on sure foundations and rising from a firm basement safely to the highest story, he says of the exact sciences: "They all build from above, and not one of them has found a basement yet-not even physics." This is indeed true. The metaphysical problems do not float above us far off in the clouds while we peacefully do our work on the firm, enduring earth, but they are rather beneath us, and our clear empirical knowledge rests on their mysterious depths like the sun-reflected sails of a ship on dark waves. So long as this is so, man can not satisfy himself with the " unknowable " and the " ignorabimus " of positivism, but will constantly seek to fathom these bafflingly mysterious depths on which he is borne along. In this book, however, no attempt is made at a metaphysical solution of instinct
(32) or any other problem. Metaphysics, or the first .science, as its original name signified, should rather be called the last science. It belongs to the end rather than to the beginning of an inquiry. So it will be at the close of my book on human play that I shall speak of the metaphysical side of my subject, if at all. For surely whether its use is justifiable or not, the time is past when it could be appealed to as a means of approaching a subject before empirical research was attempted. The merely metaphysical grounding of phenomena will never again suffice.
As a result of this empirical tendency we see a strong opposition to the transcendental-teleological view arise in the second half of our century. It assumes the form of a double criticism, a negative and a positive. The one wishes to eliminate the word instinct altogether wherever possible. The other gives to it a new meaning, no longer involving the supernatural.
The repudiation or rejection of the conception of instinct arises from the fact that the attempt is made to explain all instinctive acts as the result of individually acquired experience and reflection. Of the many who have adopted this view, I notice only the more modern.
Turning first to the great work of Alexander Bain, The Senses and the Intellect, we find there a long chapter on instinct, but in it no mention is made of the actions which we are usually accustomed to speak of as instinctive. Only reflex movements, such as heart beats, breathing, coughing, sneezing, gestures, etc., are referred to. Bain's view of real instinct is first developed in the
(33) section on " Associations of Volition," where he seeks to show that such instinctive acts are acquired by individuals rather than inherited. In his companion work, The Emotions and the Will, he teaches, too, that heredity only explains the simple movements that can be attributed to reflex action. The development of these to complicated instinctive acts, he says, depends on the individual performance of the animal.
Alfred Russel Wallace was formerly another opponent of the idea of instinct. He differed from Bain in denying to the word its application to even simple reflex action. " It is sometimes absurdly stated that the newborn infant 'seeks the breast,' and this is held to be a wonderful proof of instinct. No doubt it would be if true, but, unfortunately for the theory, it is totally false, as every nurse and medical man can testify. Still, the child undoubtedly sucks without teaching, but this is one of those simple acts dependent upon organization which can not properly be termed instinct any more than can breathing or muscular movement." 
Wallace believed, moreover, as Bain does, that instinctive acts must be learned by each individual. This appears most clearly in his brilliant essay on The Philosophy of Birds' Nests.
It is generally asserted that birds would build nests like all others of their kind even if they had never seen them. That would undeniably be instinctive. " This point, although so important to the question at issue, is always assumed without proof, or even against proof, for the known facts are opposed to it. Birds brought up from the egg in cages do not make the characteristic nest of their species, even though the proper materials are supplied them, and often make no nest at all, but rudely heap together a quantity of materials."
" With regard to the song of birds, moreover, which is thought to be equally instinctive, the experiment has been tried, and it is found that young birds never have the song peculiar to their species if they have not heard it, whereas they acquire very easily the song of almost any other bird with which they are associated." For Wallace, such cases are accounted for by simple imitation and in a slight degree by adaptation of the individual to new conditions. However, he does not consider it impossible that the existence of pure instinct may be proved in some cases. 
Later, Wallace changed his view entirely, and admitted inherited instinct. " Much of the mystery of instinct arises from the persistent refusal to recognise the agency of imitation, memory, observation, and reason as often forming part of it"; but with these elements depending on individual effort, he recognises the force of inheritance as one of the actual elements of
(35) instinct. Indeed, he approaches Weismann's standpoint on this question, as I do.
The discussion took on a more polemic form in Germany. Materialism made the attack. Carl Vogt, in the last chapter of his Pictures from Animal Life, speaks contemptuously of " so-called instinct." Brehm in his great work employs all the eloquence at his command against the " impossible doctrine of so-called instinct in animals." And Büchner follows him with an exhaustive discussion. All these writers agree in attacking first the theological conception, to which their materialistic point of view is, of course, fundamentally opposed. And they naïvely assume that any other point of view is out of the question. Thus we find in Buchner this remarkable definition: "Men have fallen into strange ignorance and conceit in calling the unknowable soul-expression of animals instinct, a word derived from the Latin instinguere (to stimulate or incite), and therefore necessarily implying a supernatural stimulator or inciter."  When the materialists become acquainted with Darwin's positive criticism of the old instinct idea, they agree indeed with it, but, passing by with slight notice his theory, they were not disturbed in their polemic against the " unfortunate word instinct." Büchner, especially, protests in several of his works sharply and persistently against the use of the word. He dwells on its variability of signification and on its mistaken employment, and considers parental teaching and individual experience and reflection the true sources of actions usually called instinctive. Ile points out after careful study that " the most of what was formerly ascribed to instinct
(36) may be explained in ways altogether different and more natural, either as produced by genuine reflection and choice, or by experience, instruction, and information; or by practice and imitation; or by a particularly good development of the senses, especially of smell; or by custom and organization; or by reflex action, etc. For example, when the caterpillar uses the fibre which Nature provides for building its nest, for hanging itself from a tree and thus eluding the pursuit of its enemies; or when caterpillars shut up in a drawer eat off the paper lining and use it for making a cocoon; or when toads persist in devouring great quantities of ants which taste good but which they can not digest, although they know (?) that pain and illness must be the consequence; or when bees passionately consume honey mixed with brandy, which maddens and unfits them for work; when birds build their nests near human habitations for the purpose of using material such as thread and woollen scraps; or when, according to the observations of G. H. Schneider, certain crustaceans in captivity use bits of cloth and paper to hide under in the absence of weeds, though when both are present their choice is always in favour of the vegetable substance; or when bees, presented with a set of prepared cells, stop building cells and carry their honey to the finished ones; or when birds prefer an artificial nest box or an appropriated nest to the product of their own skill; or when ants seize strange nests in the same way and establish themselves comfortably there instead of building for themmelves; or when many kinds of bees, instead of collecting their own honey, get a supply by robbing other hives; or when animals imitate the voice or the cries of other animals happening to be near for purposes of defence or enticement- in these and a thousand similar
(37) cases whose enumeration would fill a whole book, instinct can not be the cause or the occasion of a single one of such actions."
The wealth of examples with which the author cleverly overwhelms us might be convincing to an uncritical reader. In truth, however, Büchner combats only the most extreme conception of instinct, that is hardly to be taken seriously in our day; just as in his antagonism to theology and metaphysics he attacks with his materialistic weapons only the extremest orthodoxy and the most abstruse speculation, but in such a manner that an unlearned reader might well get the impression that theology and metaphysics generally had received their death blow. What Büchner refutes is the idea of a direct and miraculous imparting by God to the animals of absolutely inflexible and inerrant instincts. It is surely possible to reject this view and yet believe in an instinct which acts under normal conditions suitably to ends, as inborn capacity in man and beast, without individual experience and without a knowledge of the end, but which may vary under different circumstances, and become in abnormal cases so unsuited to the supposed end that it may be said to "err." Moreover, Büchner and the other opponents of instinct can by no means claim that their idea is altogether contrary to the pre-Darwinian view, for the extreme instinct theory briefly outlined above was not by any means universally held even before Darwin. Thus Reimarus, who has been quoted already, and who was easily the most influential animal psychologist of his time, his General Observations on the Impulses of Animals pass-
(38) -ing through many editions and being translated into French and Dutch-in this work (§ 98) Reimarus says: "The mechanical instincts of animals are not so fixed in every point that the creature is not left the power to modify them according to circumstances and the extent of his own knowledge." And the first sentence of § 101 runs thus: " Animals may sometimes err in their impulses, though this seldom happens when they are entirely left to themselves."
The denial of inherited instinct can in no wise be regarded as established. Reimarus himself has controverted, on grounds which in essentials are not yet obsolete, those who regard instinct as an empty or meaningless word. For example, he says in § 93: "Many mechanical instincts are practised from birth without experience, instruction, or example, and yet faultlessly. They are thus seen to be certainly inborn and inherited . . . . This is the case with all insect grubs that envelop themselves with a spun web, such as wasps and many caterpillars, bees, and ants. How can a worm that has lived scarcely a day, and that shut up in the dark ground or a little shell, possibly have acquired of itself such skill from experience or from lessons and examples?
(39) The same question may be asked about the animals that are hatched out by the sun on the sand, and as soon as they creep out of the egg hurry to the water without being shown the way; of the young duck, too, that in spite of the cries of the clucking hen betakes itself to the strange element. We have incontrovertible proof also that the mechanical impulses are innate and inherited in animals that are taken living from the mother's womb, and so could not by any possibility have seen any others or have learned to act as they do. The celebrated Swammerdam has made such an experiment with the water snail, which is born alive. He took a little one just ready for birth and placed it in water, where it immediately began to move about quite as well as the mother could. And this implies great skill, for, in order to sink, these snails retire into the shell and compress the air contained in the end-chambers, thus becoming heavier than the water. To rise, they come out a little, causing the inclosed air and their own body to occupy more space and so become lighter than the water. For surface swimming they turn over so that the shell is like a boat, the feet are extended on both sides, and an undulating movement like that of the land snail sends it slowly over the water. This skill and readiness in movement the snail cut from its mother's body has certainly not learned nor practised, but brought already developed into the world." I may here point out that Reimarus very rightly emphasizes the difficulty of learning an entirely new kind of movement. If, for example, sucking the breast " were not innate skill, go to speak, there is no reason why grown people should not do it as well as children, particularly as they are practised in various movements of the mouth, and even in sucking at other soft tubes. But, speaking for my
(40) self at least, I must own that I can no longer do it " (§ 138). 
It would hardly be necessary to cite further examples of inherited instinct if the principle involved were not so vital to my purpose. As this is so, I give the views of two modern philosophers who both defend the idea of instinct, though from very different standpoints and without being in any special sense Darwinians.
E. von Hartmann gives the following among a great many other examples: " Caterpillars of the Saturnia pavonia minor eat the leaves of a shrub as soon as they emerge from the egg, go underneath the leaves when it rains, and change their skin from time to time; this is their whole existence, and in it not the least evidence of intelligence can be found. But the time comes for spinning their cocoon, and they build it firm and strong, with a double arch formed by gathering the fibres together at the top, so that they are very easy. to open from the inside, but offer considerable resistance to any external force. Were this arrangement the result of conscious intelligence, a chain of reasoning something like this would be necessary: ` I am now approaching a chrysalis state, and, immovable as I am, I shall be exposed to attack; therefore I will inclose myself in a cocoon. Since I shall not be in a condition as a butterfly to effect an exit either through mechanical or through chemical means, as many other caterpillars do, I must therefore provide an opening. But at the same time,
(41) that this opening may not be used by my enemies, I must use such an arrangement of the fibrous web as will allow me to push out but will yet offer resistance to outside pressure, according to the principle of the arch.' This does seem too much to expect froth the poor little caterpillar." 
Wundt cites the same example, originally suggested by Autenrieth, as especially significant, and says, moreover: " If it were actually through a capacity for adapting means to an end that the bird produces its nest, the spider its web, and the bee its cell structure, a degree of intelligence would be required that man himself, in the course of a mere individual life, would hardly be capable of. A further proof of the fallacy of such an explanation is the regularity with which certain actions are performed by individuals of the same species where there is not always any association between them. Such association, of course, exists among the bee and ant tribes and among those animals whose young remain for some time after birth with their parents, but in numerous other cases the little creature begins its life independently. When the caterpillar creeps out of the egg its parents are long since dead, yet it prepares a cocoon like theirs. And, finally, there are many cases where the instinct-acts that seem to be intelligent appear to include a direct foresight of the future. How can this foresight possibly be intelligent when there has never been analogous experience in the individual's life? Nor has it received information in any way. When the moth incloses its eggs in a furry covering made of its own hair, the winter, which makes this warm wrapping necessary
(42) for the preservation of the egg, has not yet come. The caterpillar has never experienced the metamorphosis for which it prepares." 
I conclude with a few examples from the numerous witnesses among modern scientists. " The instinct for flight to warmer lands," says Naumann, "is born in migratory birds. Young ones taken from the nest and allowed to fly about freely in a large room sufficiently prove this. They circle about their prison at night, during their time of migration, just as the old birds do in confinement." Douglas Spalding experimented as Swammerdam also did. He took little chicks from the egg, put caps on them that covered the eyes until they were two days old. When these were removed one of them at once followed with its eyes and head a fly some twelve inches away. A few minutes later it picked at its own toes, and in the next moment sprang vigorously after a fly and devoured it. It ran at once, with evident assurance, to a hen brought near, and seemed to need no experience or association in all this to enable it to go over or around impediments, for these were its first lessons in life. Spalding has also shown experimentally that young swallows can fly without teaching as soon as they reach the proper age. Further he relates: " One day, after I had been stroking my dog, I reached my hand into a basket which held four blind kittens three days old. The smell of my hand made them spit and hiss in a ridiculous way." Romanes succeeded in mak-
(43) -ing a quite similar experiment with young rabbits and ferrets. Hudson once found some eggs of the Parra jacana. " While I was looking closely at one of the eggs," says he, "lying on the palm of my hand, all at once the cracked shell parted, and the young bird quickly leaped from my hand and fell into the water. I am quite sure that its sudden escape from the shell and from my hand was the result of a violent effort on its part to free itself, and it was doubtless stimulated to make the effort by the loud, persistent screaming of the parent birds, which it heard while in the shell. Stooping to pick it up to save it from perishing, I soon saw that my assistance was not required, for immediately on dropping into the water it put out its neck and with the body nearly submerged, like a wounded duck trying to escape observation, it swam rapidly across, and, escaping from the water, concealed itself in the grass, lying close and perfectly motionless like a young plover." 
Weinland reports of the snapping turtle: " For months these turtles emerge daily from eggs laid in the sand and moss, and it is noteworthy that the first movements of the little heads thrust out of the broken shell are those of snapping and biting."
Preyer and Binet are firmly convinced that instinct is the source of the child's first attempts to walk. According to Binet's observations, children only a few weeks old really take measured steps when held up so that the soles of their feet rest on the floor. In short,
(44) James is perfectly right when he says that the sitting hen, for example, needs no further experience or psychic process than the feeling that the egg is just " the-never-to-be-too-much-sat-upon object."
From all this it appears that there is no doubt that inherited instincts exist, and that a positive rather than a negative criticism will be needed in dealing with this idea, which, indeed, is much easier to affirm than to explain. We at once reach the conclusion, however, that it is necessary to eliminate from the definition of instinct the transcendental-teleological method of conceiving it - a task which has been attempted by the promulgators of the Lamarck-Darwinian theory. " An important reason for the slow advance of scientific knowledge is the universal and almost unconquerable adherence to teleological conceptions, which are substituted for distinctly scientific ones. Nature may affect us ever so impressively and ever so variously, but it is all lost upon us because we look for nothing in her manifestations that we have not already read into them; because we will not permit her to make the advances, but are always trying with impatient, ambitious reasoning to approach her. Then, when in the course of centuries there comes one who draws near to her with a quiet, modest, and receptive mind, and lights upon innumerable phenomena which we, by our preoccupation, have overlooked, we are amazed indeed that so many eyes should not have seen them before in such clear light. This striving with unnecessary haste after harmony before the various tones which should compose it have been collected, this violent
(45) usurpation by the intellectual powers of a realm where they have not undisputed sway, explain the unfruitfulness of so many thinkers for the advancement of science. It is difficult to say whether mere sentiment, which assumes no definite form, or mueh reasoning tending to no purport, has interfered more with our progress in knowledge." But who has written this masterly indictment of modern science? I fancy that one would not easily detect the author did not certain artistic expressions betray him, and withal the perfect style which is as brilliant and as penetrating as a good sword.
Lamarck published his theory of development in 1801, and extended it in the Philosophie zoologique, which appeared in 1809, as well as in the introduction to his work on the Histoire naturelle des animaux sans vertèbres. As the fundamental principle of his theory, he lays down the inheritance of acquired characters by individuals (especially functional adaptations). Darwin included this principle in his theory advanced in 1859, but perfected it by his more important and comprehensive conception of natural selection. According to it, not only functional adaptations, but also the inheritance of congenital characters produce changes in species, so that in each generation congenital " individual variations " appear of which the " fittest " always come out best in the struggle for existence, and are thus transmitted further (Spencer, Survival of the Fittest). In the whole organic world this principle rules, adapting meant to ends without there being any endthat is, any conscious of voluntary end. The transcen- dental-teleological principle is thus excluded. "The
(46) useful becomes the necessary as soon as it comes to be possible."
Darwin himself attached greater importance to congenital qualities than to the inheritance of acquired ones, as clearly appears in his definition of instinct. He says in his Origin of Species: "It would be the most serious mistake to suppose that the greater number of instincts have been acquired by habit in one generation, and then transmitted by inheritance to successive generations. It can be clearly shown that the most wonderful instincts with which we are acquainted- namely, those of the hive-bee and of many ants--could not possibly have been thus acquired." And in the Descent of Man: " Some intelligent actions--as when birds on oceanic islands first learn to avoid man--after being performed during many generations become converted into instincts, and are inherited . . . . But the greater number of the more complex instincts appear to have been gained in a wholly different manner through the natural selection of variations of simpler instinctive actions." 
We see, then, that Darwin derives instinct from two distinct sources. The principal source is natural selection; the less important is the inheritance of intellectual capacity and then of acquired characters. Romanes follows him closely in his distinction between
(47) primary and secondary instinct. He says: " I shall allude to instincts which arise by way of natural selection, without the intervention of intelligence, as primary instincts, and to those which are formed by the lapsing of intelligence as secondary instincts." 
Romanes in turn has influenced some other animal psychologists. Thus Foveau de Courmelles says, in elaborating Romanes' distinction: " The primary instincts consist of non-intelligent habits devoid of adaptability, transmissible by heredity, themselves subject to variation and liable to become fixed. Secondary instincts are intelligent adaptations that have become automatic and hereditary."  And Lloyd Morgan, who refers to Romanes's treatment of the instinct idea as most masterly and admirable, likewise adopts the division into primary and secondary instincts, but, owing to the influence of Weismann and Galton, is very cautious about approaching the subject of the inheritance of acquired characters, and, consequently, that of secondary instincts. He accordingly attributes to these principles only a probable value. 
The great majority of modern animal psychologists, however, explain instinct by the Lamarckian principle of the inheritance of acquired characters alone, or almost alone. Their conception of instinct is something like this: Darwin had already pointed out its analogy to acts
(48) in individual life which have become reflex through practice and repetition; the piano player reaches for the right key "mechanically," intuitively, though at first he could make the same movement only under the control of conscious will. In just the same way inherited instinct depends on a " lapsing of intelligence " (Lewes), but instead of being accomplished in a single life, it progresses in such a manner that the conscious practice of earlier generations becomes the reflex activity of later ones. This is what is meant by the common designation of instinct as inherited habit or hereditary memory. I cite only a few examples: Preyer and Eimer use these expressions in defining instinct, and L. Wilser calls it hereditary skill or aptitude. Wundt says, "Movements that originally appeared as simple or compound acts of the will, but later, either in the life of the individual or in the progress of race development, have become partially or entirely mechanical, we call instinctive acts." Th. Ribot, with Lewes, calls instinct "conscience Reinte," and Schneider refers what he recognises as hereditary in instinctive acts to the practice and habit of ancestors. Thus he explains our instinctive fear in the dark as the inheritance of acquired association:
(49) " Not only our savage ancestors but even those of later times who have not had the good fortune to live, as we of the present do, in circumstances rendered secure by orderly government, could not undertake the slightest journey, especially by night, with the carelessness with which we now in middle Europe tramp through the loneliest mountain pass or traverse the densest woods by day or night. They had much to fear from wild animals, especially bears, and from men, such as highwaymen and the famous robber knights, and in lonely woods and passes were never safe. Moreover, the feeling of fear which besets the young, especially when travelling alone on a dark night in a lonely wood or valley, is so universal that we are forced to connect it with the common experience of earlier generations, and consider it an inherited feeling."
If this reference of instinct to the inheritance of acquired characters which we find is so general be correct, play can be explained about as follows: Our ancestors have throughout their whole lives made use of their arms and legs for every possible movement; accordingly, their descendants have in their earliest infancy the impulse to kick with the legs and to grasp everything in their hands. The forbears hunted animals; hence the hunt and chase games of the descendants. Our ancestors were obliged to hide from their enemies in a thousand ways; hence the hiding games of children. Thus Schneider says: " The boy does not now eat the sparrows, beetles, flies, and other insects that he ea6gerly seizes and perhap, team to piece, nor does he intend to devour the young birds that he takes from their nests in high trees, often at the peril of his
(50) life; but merely seeing these things wakes in him a strong impulse to plunder, hunt, and kill, apparently because his savage ancestors commonly gained their subsistence by such means. There is in him an intimate causal connection between the sight of certain free animals, or birds' eggs, and the impulse to plunder, slay, and rend. That this was the case with our animal ancestors we are convinced from the life of modern apes, which is sustained principally by means of spoil taken from smaller animals, especially insects, young birds, and birds' eggs." " Girls, as well as boys, show in their play unmistakable signs of having inherited the characteristic habits of the race." Thus play becomes the result of intelligent activity .of preceding generations, a form of hereditary skill.
In the last decade, however, the general conception of instinct has undergone an essential transformation through August Weismann's neo-Darwinism. I can not here, of course, go thoroughly into the highly complex grounds of this theory of heredity. Weismann postulates an hereditary substance carried on continuously through succeeding generations, the germ plasm (Keimplasma ) which is present in the so-called chromosomes, or colourless bodies of different shapes inside the cell nuclei ("chromatin bodies " or " chromatin nuclei "). He not only asserts in a general way that this substance inside the germ cells must have an exceedingly
(51) complicated structure historically handed down, which, indeed, is undeniably the case, but in a more daring hypothesis he attempts to establish the essential elements of this structure: the molecules of germ plasm go in various ways to form Biopliores, which determine the cell qualities; these in turn form Determinants, which again find their higher unity in the Ide;  these, again, are grouped in the Idant, which is identical with the chromosome.
But this world of minute elements represented by the germ cells is, as I said before, continuous- that is, it is not produced anew in each individual, but persists with great stability throughout the countless successions of related life forms, building up organisms but never exhausted in the process, and not influenced by individual experience or by heredity. It may be figured as a creeping root, stretching far from the parent stock; single plants rise from it at different points, represented by the individuals of successive generations. If, then, a material so constituted is the only medium for the operation of heredity, there can be no transmission of acquired characters.
Weismann's theory taken as a whole is far from universally recognised as established. It has a great number of opponents, of whom I mention only Haeckel,
(52) Eimer, Wilser,  Hertwig,  Romanes, [69 ] Herbert Spencer, Wundt,  Sully,  and Ribot.  The truth is, it is not yet given to us entirely complete, for almost every work of the gifted author yet published shows some modification more or less important. The weightiest point to be determined before the theory can be further developed is that of the relation of the individual to the hereditary substance or of the soma to the germ plasm. Does this germ plasm pervade the endless series of individuals with absolute continuity, changing only through its combination with that of other individuals (amphimixis)? Weismann formerly appeared to attribute absolute persistence to the germ plasm; indeed, he has, in one instance at least, emphasized this doctrine. Yet in 1886 he admitted that monads that are propagated by mere division may inherit acquired characters. In 1891 he limits this possibility to unicellular structures without a nucleus. In other directions, however,he has
(53) weakened this position by the admission that the germ plasm may have only a " very great " but not absolute persistence. I do not refer to his granting the inheritance of diseases (these are, after all, only pollutions of the stream that may not essentially alter it), but to his admitting the possibility of modifying the germ plasm by changing nutriment and temperature.
Next in order is his essay on External Influences as Aids to Development (1894), where he shows that he is not blind to the importance of external conditions. He here concedes that the development of germ plasm itself may be modified by means of changes in nutriment and temperature, while predispositions that remain latent under ordinary circumstances may be stimulated to activity by such "external aids." The fact that this is not the cause but only the occasion of the modification is especially emphasized, the cause being always the predisposition latent in the germ. That the persistent quality of the germ plasm was only relative had already been clearly intimated, however, in his more important work, Das Keimplasma, 1892, p. 526. Speaking of a butterfly, which has bright or dark wings, according to the climate, he goes on to say: " The modifying influence, here temperature, affects in each individual both the fundament of the wings - that is, a portion of the soma - and also the germ plasm contained in germ cells of the organism. In the wing-fundament the same determinants change as in the germ-cells - namely, those of the wing-scales. The first modification can not influence the germ cells, and so affects only the colour of the wing
(54) belonging to the one individual; but the other passes over to succeeding generations and determines the colour of their wings so far as they are not further modified by later temperature conditions." It is only by means of such variations in the germ structure, brought about by external influences, that Weismann can now find a possible explanation of the origin of new species.
I now pause to gather up these positions. Weismann's theory is not sufficiently defined by the thesis: there is no inheritance of acquired characters; for, in the first place, he grants such inheritance in the case of unicellular structures without a nucleus, where his distinctions between morphoplasm and ideoplasm, somatogen and blastogen do not hold; and, secondly, while there is indeed for him no inheritance of acquired characters among individuals of the higher forms of life, there is the inheritance of the acquired characters of germ plasm. For conditions which influence an individual organism may take effect in the hereditary substance present in it and produce inheritable changes in that substance. Acquired variation in the individual may run parallel, under certain conditions, with acquired and inherited variation in the germ plasm, but is never the cause of it. They are simultaneous reactions from a third condition-namely, the external influence. So it appears that what is usually meant by the phrase inheritance of acquired characters- namely, the carrying over from one generation to another of acquired characters of the body- is actually excluded by Weismann's theory. 
(55) It is undoubtedly true that Weismann has seriously shaken the faith in inheritance of acquired characters which formerly played so important a rôle in philosophy, especially in the departments of ethics and sociology. He accomplished this quite as much by his searching criticism of the Lamarckian principle as by his own complicated theory of heredity. Even adherents of the Lamarckian system admit that its principles were rather too easily assumed. And, fortunately, one can speak of a neo-Darwinism as opposed to neo-Lamarckism without being pledged to all the mysteries of Biophores and Determinants, Ides and Idants. Galton, an author whose stirp theory is in many respects analogous, is very sceptical in regard to the inheritance of acquired characters, if he does not abso-
(56) -lutely deny it. Similar opinions are held by James, Virchow, Meynert, His, Ziehen, O. Flügel, Wallace, Ray-Lankester, Thiselton Dyer, Brooks, Baldwin, Van Bemmelen, Spengel, and many others. A. Forel has also joined their ranks. He says: " I, too, used to believe that instincts were hereditary habits, but I am now convinced that this is an error, and have adopted Weismann's view. It is really impossible to suppose that acquired habits, like piano playing and bicycle riding for instance (these are certainly acquired), could hand over their mechanism to the germ plasm of the offspring."
The transition to the idea, of instinct is easy at this point, for, even according to the latest formulation of Weismann's theory, it is quite impossible that the intelligent actions of ancestors should be transmitted to their descendants as instincts. Even if a modification of the hereditary substance should take place it would not originate in the intelligent act, but in the external conditions that impelled the individual to perform the act. Let us take Schneider's example of fear in the dark. Our ancestors frequently encountered in the dark the terrible cave bear. This repeated experience most probably produced in their brains an acquired sensory motor tract: " Dark-be wary! " Now, is it at all conceivable
(57) that a variation parallel with this can have been effected in the reproductive substance through which predispositions arose that at once produced a similar tract in the brains of their descendants? This is incredible. It follows, then, since by supposition only the external environment and not the bodily changes work upon the germ plasm, that any explanation of instinct by means of the inheritance of acquired characters is quite impossible. There remains, then, to be considered in this example only the explanation by means of selection, the Darwinian position. This is simple enough, supposing it to be really a case of heredity (as I do not pretend to affirm categorically): it has always been the case that more of those individuals perished who were inclined to walk about carelessly in dark caves and woods.
Weismann himself has not neglected the question of instinct. He said as long ago as 1883 that all instincts have their roots not in the acts of individuals, but rather in germ variation. In the same lecture lie also pointed out that many instinctive acts are performed only once in a lifetime-for instance, the flight of the queen bee-and would thus be inherited without practice.  And in a paper on the Allmacht der Naturzüchtung, 1893, he cites a highly interesting example which seems to exclude every explanation other than that of selection. It concerns, on the one hand, the origin of physical characters and of instincts, and on the other the decadence of the latter. In this ease the inheritance of acquired characters is out of the question, as the subject is a sterile individual. The workers among ants are known to be sterile. Among
(58) some species the female workers have the slaveholding instinct. This instinct must have arisen before the species had sterile workers (they have developed from females originally productive); for all the intermediate stages are known between those which hold no slaves at all and those which always do it. The Formica sanguinea do not yet show the slaveholding tendency as a fixed and demonstrable characteristic of their species, nor have they the extraordinary physical modification that marks the Polyergus refescens, settled slaveholders. Accordingly, we have here two developmental stages with clearly marked instincts. It is between these two stages that the variation to sterile workers must have taken place. The jaws must be changed from working tools to deadly weapons, as well as become adapted for carrying; they have become sword-sharp pincers, sharp and strong, suited alike for seizing and bringing home the young from other nests and for boring into the heads of enemies. At the same time the instinct for plundering is enormously strengthened. And here the hereditary effect of practice can not possibly be argued. The sterile workers could not possibly transmit anything, and their progenitors possessed neither such organs nor such instincts. On the other hand, the domestic instincts are weakened; workers of the Polyergus neither care for the larva nor collect food and building material. In fact, they seem to have lost entirely even the capacity to recognise and appropriate their own proper nourishment. " Forel, Lubbock, and Wasman are all convinced that the assertion made by Huber long ago is entirely correct. I have repeated his experiment, as well as Forel's, with the same result. These insects starve when confined, if none of their slaves are at hand to feed them. They do not recognise a drop of honey as something that will
(59) satisfy their hunger, and when Wasman placed a dead pupa actually in their jaws, they made no attempt to eat it, only licked it inquiringly, and left it. But as soon as one of their slaves- that is, a worker of the Formica fusca --was introduced, they approached and begged it for food. The slave hastened to the honey drop, filled her mouth, and brought the food to her ladyship."
What a splendid example this would be of the hereditary effect of disuse, says Weismann, if only these workers were not sterile! As the unreasoning conduct of these workers excludes the idea that their behaviour springs from the judgment of individuals, there remains for an explanation only selection, and selection of the mother at that. It must be noted, on the one hand, that those ant communities are more thriving whose productive females bring forth workers whose individual variations are in the direction of the decided modifications in physical qualities and in instinct mentioned above. On the other hand, if the force of selection relaxes with reference to the weakening instinct, there results a community where the fruitful females produce workers whose instinct for collecting, rearing the young, and foraging is constantly diminishing (negative selection or panmixia).
Instances like this must increase the doubt about the inheritance of acquired characteristics. Let us now turn our attention to some other arguments for neo-Darwinism. To its advocates the fact is very significant that not a single example seriously threatening Weismann's theory has been brought forward by their op
(60) -ponents. Many of the cases cited with that in view are scientifically unreliable, and the rest can be explained quite well by the principle of selection. If acquired characters were hereditary, what an instinctive predisposition there would be for such acts as writing, for instance!-and Spencer would be able to ascribe Mozart's precocious musical talent to the practice of a few previous generations! It should further be borne in mind that the long-continued experiments of Weismann and others have never produced a positive instance of such transmission. Darwin himself was interested in the question. Romanes tells us that in 1874 he had a long conversation with him on the subject, and undertook a systematic series of experiments under his direction. He continued them for more than five years almost uninterruptedly, but they were all unsuccessful; so he, too, found it impossible to establish the truth of the inheritance of acquired characters.
As regards instinct, there is, further, the a priori argument that it is inconceivable how acquired connections among the brain cells could so affect the inner structure of the reproductive substance as to produce inherited brain tracts in later generations. And, finally, there is this consideration mentioned by Ziegler as a suggestion of Meynert's: " It is well known that in the higher vertebrates acquired associations are located in the cortex of the hemispheres. As an acquired act becomes habitual, it may be assumed that the corresponding combination of nervous elements will become more dense and strong and the tract proportionally more fixed. This being the case, it follows that the tracts of acquired and habitual association, as well as those of
(61) acquired movement, pass through the cerebrum. Instincts and reflexes, however, have their seat for the most part elsewhere. The tracts of very few of them are found in the cortex of the hemispheres. It is chiefly in the lower parts of the brain and spinal cord that the associations and co-ordinations corresponding to instincts and reflexes have their seat. When the comparative anatomist investigates the relative size of the hemispheres in vertebrates (especially in amphibians, reptiles, birds, and mammals), a very evident increase in size is observed which apparently goes hand in hand with the gradual gain in intelligence. In the course of long phylogenetic development, during which the hemispheres have gradually attained their greatest dimensions, they have constantly been the organ of reason and the seat of acquired association. If, then, habit could become instinct through heredity, it is probable that the cerebrum would in much greater degree than is the fact be the seat of instinct."
But what part has psychology had in this war of opinions? It is impossible for her to give a satisfactory answer to this question. She must pick her way cautiously, and in the matter of instinct the adoption of the neo-Darwinistic theory is evidently the most prudent course, for to it belongs the now universally recognised principle of selection. Accordingly, when I speak of instinct it will be in accordance with this idea of innate hereditary variations, passing by the Lamarckian theory as either obsolete or a point of view yet to be substantiated. In what follows I adhere in essentials, to the definition that Ziegler, a follower of Weismann, has given in
(62) the address already cited, with the exception of one point, which I shall indicate at once. Ziegler has set forth with great skill, clearness, and technical scholarship a point of view which is now more and more attracting the attention of modern zoölogists; and the leading features of his exposition coincide with the views of many modern psychologists. In all instinct there is a close connection between a particular stimulus and a particular act, a connection that is of utility under ordinary conditions. Is this useful adjustment attributable to conscious will? No. On the contrary, the idea of consciousness must be rigidly excluded from any definition of instinct that is to be of practical utility. (Who can tell whether a dog, a lizard, a fish, a beetle, a snake, or an earthworm performs an action consciously or unconsciously? It is always hazardous in scientific investigation to allow a hypothesis which can not be tested empirically.)
It follows, that such fixed and useful connections between stimulus and action are to be treated as reflexes. Instincts are, as Herbert Spencer has rightly said, complex reflex acts. But the connection between reflex action and instinct is explicable only by means of selection, and selection in the Weismannian sense, which excludes the inheritance of acquired characters. " In the progress of phylogenetic development natural selection lays the foundation of instincts, and accordingly they are useful. Instincts are adapted to conditions, and serve generally for the preservation of the individual, always for that of the species." There must be, physiologically speaking, certain connecting paths among the ganglion cells that--existing as hereditary predispositions--contain " hereditary tracts."
The complexity of instinct that is often so baffling, and its wonderful adaptiveness are, after all, not more difficult to explain than the other things about an organism. For example: "The marvellous instinct that leads the wood bee (Xylocopa violacea Fabr.) to build its intricate nest in the trunks of trees is not more inexplicable than the faceted eyes of these very insects . . . . The principles involved in the morphological structure of the organ also account for the instincts; and there are also to be taken into account homology, analogy, and parallel development, individual variation, natural selection, and the resulting adaptation, cross-breeding, and atavism; here also there are cases of rudimentary and hindered development, natural or artificial deformity." No part can be had, in the genesis of instinct, by association resting on a foundation of previous experience, what we mean by understanding, intelligence in its widest sense; nor by acquired tracts, for these are not hereditary.
After giving this elaboration of Ziegler's theory in his own terms, I make these essential points:
1. The assumption that intelligent acts are the ground of the origin of instinct is unwarrantable. Even if the Lamarckian theory is not absolutely tabled, it is much wiser, so long as the question remains open, to be content with the leading Darwinian principle, since its grounds are more assured.
2. In the explanation of instinct (and of play) we need consider only natural selection, for we do not know any other principle of development. The simple reflex action must develop in the process of lime into the complex reflex actions that we call instinctive. In this way we try to explain their adaptability as well as we explain organic adaptability in general. Whether it can be satisfactorily done is another question. I am not one of the
(64) number who believe in the " all-sufficiency of natural selection." Leaving out of the question the fact that our knowledge of phylogenesis rests finally on the mysterious ocean of metaphysical problems, of which I have spoken, it is by no means settled, even in the sphere of empirical science, that selection of ordinary individual variation suffices to bring about, even gradually and by minute degrees, a change from one species to another. There are those who deny this, to whom the Darwinian system is comparatively insignificant. As in surging water the particles of each wave move both backward and forward, so that the surface motion forward is really only apparent, so the selection of hereditary qualities can not extend beyond a certain definite point, and for the transformation to new species other and essentially different variations are necessary, in their opinion, in the structure of the germ substance itself.
Nevertheless, we know no principle except that of selection, and we must go as far as that will take us. Absolute knowledge of such phenomena is practically unattainable. 
3. Since instincts, according to Spencer's view, already explained, are only complicated reflex acts, the question may be excluded whether animals acting instinctively are conscious in play of what they do. It is evident, of course, that many instinctive actions are accompanied by consciousness, but seeing that even the instincts thus consciously practised are probably derived from unconsciously perfected reflexes, it is impossible to draw the line.
Ziegler is more cautious than Romanes and Schneider, who attempt to find a definite boundary line between
(66) instinct and reflex action according as consciousness is present or not. In the opposite direction, he is more cautious than Ziehen, who accepts the hypothesis of the absolute unconsciousness of instinctive acts. Ziegler is probably influenced here, as on other points, by Herbert Spencer, who thus guardedly expresses himself: " Instinct in its higher forms is probably accompanied by a rudimentary consciousness."  So far I agree with Ziegler, but his avoidance of any definite expression of opinion as to whether consciousness is or is not present is significant in another connection, and here, as I think, he is not entirely in the right. Every instinctive act is a means for preserving the species. This fact gives the question of consciousness a double significance, as Hartmann's definition, for example, clearly shows: " Instinct is the conscious willing of means to an unconsciously willed end." 
As concerns the means, that is, the act itself, it is safer, as has been remarked, to avoid the terms " conscious " and " unconscious " altogether. But it seems permissible to say, at least with reference to the end of a particular action, " by instinct we understand the impulse to an action whose end the individual is unconscious of, but which nevertheless furthers the attainment of that end." That is to say, the consciousness of an end as such is entirely separable from the instinctive act. Ziegler does not leave room for any psychic factor, not even a negative one, in his definition.
(67) "Who can know whether the bird when she builds her nest already has the knowledge that her young will find a warm bed in it? And even as applied to man this criterion is misleading. For example, when a mother suckles her child the action is evidently instinctive, though the mother perhaps cherishes the hope that the child may become the support of her old age and the representative of his family, thus knowing perfectly well not only the immediate end of her action, but also its utmost consequences." On this account Ziegler prefers not to speak of the presence or absence of consciousness of end or object. But it seems to me that the subject has quite a different aspect if we first try to make clear just what is meant by lack of consciousness of end or object. There are two widely different ways of interpreting the expression. First, there is the relativity of the end to be considered, as Schneider has justly remarked in his later work, Der menschliche Wille. When a beast of prey scents his victim, and creeps toward it with the movement peculiar to his kind, this creeping is a means to the end of approaching near enough for a spring. The spring is a means to the end of seizing the animal and slaying it. Rending the prey is a means to the end of eating it, and this in turn serves the end of nutrition, and so on. Only the last and highest end is, as far as we know, not a relative one-namely, the preservation of the species. But under present conditions only reflecting man can be conscious of this end. and even he is scarcely conscious of it in actual everyday life. There is usually only a relative consciousness of end even in our actions which are not instinctive. When a man buys a new suit
(68) of clothes he does not reflect that he is thus furthering the preservation of his kind (Schneider). As for the instinctive acts of children, savages, and animals, it may safely be affirmed that in them such adaptation of means to the end as selection requires for the preservation of the species is entirely unconscious. At the same time there may very well be consciousness of relative ends. The fox out hunting, for instance, may have a memory of gastronomic enjoyment in his mind as his end idea. I consider this first conception of activity unconscious of its end inadequate, however, because, as has been said, actions not instinctive are also often unaccompanied by a consciousness of their highest or final end.
Nevertheless, the position to be mentioned as second, combated by Ziegler, seems to me to be nearer the truth, namely, the position that an action is only instinctive when it does not include a consciousness of end, either relative or absolute, as its motive. Let us again take the fox, scenting his prey. If in creeping toward it he has a conscious end, this can only be grounded in individually acquired associations of smell with the agreeable taste of the victim, and in the recollection that it has been known to escape in consequence of careless movements on the part of the pursuer. We can not speak of instinct within the limits of such acquired association, so far as it operates as a motive. So far, on the other hand, as the mere external stimulus to the olfactory nerves of the fox excites to functional activity the hereditary tracts in the animal's brain. so far his act is just as instinctive as the Rpitting of a kitten at the hand which has stroked a dog, or the bird that builds a nest. Even if the bird does have the consciousness that its young will find a warm bed there, its action may still be purely instinctive, so long as that conscious-
(69) -ness remains a mere memory, without motive power. As soon, however, as the idea affects the will, we have no longer a purely instinctive action to deal with, but one that is partly instinctive and partly voluntary. Inasmuch, also, as conscious action often tends to become instinctive, I may take account of that fact, and accordingly formulate this approximate definition: The actions of men and animals are instinctive when originated by means of hereditary brain tracts (presumably of selective origin) and without an idea serving as their motive.
The fact that the same act may be partly instinctive and partly voluntary is of importance in many connections, not least in that of play, in which the higher the stage the more the individual accommodations are involved. Formerly extreme theorists entertained the view that only animals have instinct, only man has reason. Cuvier believed that the relation of instinct and intelligence was that of inverse ratio; Flourens, the same. Darwin opposes Cuvier's idea, but thinks that "man perhaps has somewhat less than the animals standing next him," and that the instincts of higher animals are less numerous and simpler than those of the lower orders. James, on the contrary, reverses the proportion, and says that man is probably the animal with most instincts.  This is perfectly true if it is borne in mind that some actions are partly voluntary and partly instinctive. Take, for instance, lovers of the
(70) chase, who are perfectly conscious of the object of their actions and yet are in great part impelled by instinctive impulses. If such half-instinctive phenomena are included in the category, then man has as many instincts as any animal, if not more. By this elucidation we reach the truth that lies concealed in the theory mentioned above-namely, that the lower the animal stands the purer are its instincts; the higher its place the more will the hereditary tracts be weakened, altered, or supplanted by acquired tracts. " The more various and ready the inherited mechanical impulses of a class of animals," say the Müllers, " the less do we find of independent mental capacity."  And Flourens remarks, " Intelligence does not enter into instinct, but it influences it, protects it, and alters circumstances to suit it, and this agreement between instinct and intelligence is well worth attention."
I am now firmly convinced that this relation is itself eminently useful, and that it is due to negative as well as positive selection. Hartmann has already pointed out that Nature substitutes instinct where the means are not at hand for conscious action or acquisition. The higher and more complicated the scale of activity which the struggle for existence requires of a species the more will selection favour development of the brain and of the mental capacities. The more these increase by means of positive selection the less will its aid be needed in the sphere of instinct. The result will be that fewer individuals will have completely developed hereditary tracts
(71) for future transmission. In short, where positive selection furthers the growth of intelligence, for instinct there will be a certain degree of negative selection or panmixia. (This, of course, applies only to instincts for which conscious actions can be advantageously substituted.) Indeed, it might even be said that the degeneration of instinct is due to positive selection. We have no intimation at what stage of evolution the animal world first achieves activity that depends on its own intelligence or the capacity for individually acquired association; but we may assume that at some point in the progress of evolution the creature attained sufficient intelligence to accomplish many things by means of it better than by instinct. From this moment on, extensive inheritance of brain mechanism would have been positively prejudicial to the further development of intelligence, and a positive selection may be assumed that would directly favour less finished instincts in order to produce in the nervous system a partiality for the now more useful acquired functions. 
Be that as it may, we may explain by such degeneration of instincts the countless cases which have caused such men as Wallace to doubt whether there is any instinct at all. In his chapter on The Philosophy of Birds' Nests, Wallace has collected observations intended to prove that birds do not come into possession of their songs by inheritance, but learn them individually. Barrington caged young linnets with singing larks, whose song they learned so well that, even when placed with other linnets, they did not change them. A bullfinch sang like awren and without anyof the characteristics of its own kind, and similar results were obtained from the wheat-ear, fallow-finch, nightingale, and woodpecker. " These facts," says Wallace, " and many others which might be quoted, render it certain that the peculiar notes of birds are acquired by imitation, just as a child learns English or French, not by instinct, but by hearing the language spoken by its parents." This sounds very convincing, but it is first to be considered that the use of the voice is instinctive, and then that imitation itself is instinctive, of which more is to be said below; and, finally, that the experiment failed with young birds taken from the nest when only a few days old, for they could never be influenced again in the same way by later experiences. The song of birds is no doubt a mixed phenomenon in which instinct and experience blend.
Such advancement of the evolution of intelligence as we have been considering is favoured also by play, as I
(73) believe. I trace the connection as follows: A succession of important life tasks is appointed for the adult animal of the higher orders, as for primitive man, some of the principal being as follows:
1. Absolute control of its own body. Grounded on this fundamental necessity are the special tasks, namely:
2. Complete control over the means of locomotion for change of place, characteristic of the species, as walking, running, leaping, swimming, flying.
3. Great agility in the pursuit of prey, as lying in wait, chasing, seizing, shaking. Equal fitness for escaping from powerful enemies, as fleeing, dodging in rapid flight, hiding, etc.
4. Special ability for fighting, especially in the struggle with others of the same kind during courtship, etc.
After the foregoing discussion there can be no doubt that instinct plays a part in all this adaptation for the struggle for life and preservation of the species, so necessary in man and other animals. Further- and here I again come into touch with the end of the last chapter -- it would be entirely in harmony with other phenomena of heredity if we found that these instincts appear at that period of life when they are first seriously needed. Just as many physical peculiarities which are of use in the struggle for the female only develop when the animal needs them; just as many instincts that belong to reproduction first appear at maturity;' so the instinct of hostility might first spring up in the same manner only when there is real need for it: and so it might be supposed with other instincts in connection with the related activities. The instinct for flight would only be awakened by real danger, and that of hunting only when the animal's parents no longer nourished it, and so on. What would be the result if this were
(74) actually the case- if, in other words, there were no such thing as play? It would be necessary for the special instincts to be elaborated to their last and finest details. For if they were only imperfectly prepared, and therefore insufficient for the real end, the animal might as well enter on his struggle for life totally unprepared. The tiger, for instance, no longer fed by his parents, and without practice in springing and seizing his prey, would inevitably perish, though he might have an undefined hereditary impulse to creep upon it noiselessly, strike it down by a tremendous leap, and subdue it with tooth and nail, for the pursued creature would certainly escape on account of his unskilfulness.
Without play practice it would be absolutely indispensable that instinct should be very completely developed, in order that the acts described might be accurately performed by inherited mechanism, as is also the case with such instinctive acts as are exhibited but once in a lifetime. Even assuming this possibility, what becomes of the evolution of higher intelligence? Animals would certainly make no progress intellectually if they were thus blindly left in the swaddling-clothes of inherited impulse; but, fortunately, they are not so dealt with. In the very moment when advancing evolution has gone so far that intellect alone can accomplish more than instinct, hereditary mechanism tends to lose its perfection, and the " chiselling out of brain predispositions" by means of individual experience becomes more and snore prominent. And it is by the play of children and animals alone that this carving out can be properly and perfectly accomplished. So natural selection
(75) through the play of the young furthers the fulfilment of Goethe's profound saying: " What thou hast inherited from the fathers, labour for, in order to possess it."
At this point the full biological significance of play first becomes apparent. It is a very widespread opinion that youth, which belongs, strictly speaking, only to the higher orders, is for the purpose of giving the animal time to adjust itself to the complicated tasks of its life to which its instincts are not adequate. The higher the attainment required, the longer the time of preparation. This being the case, the investigation of play assumes great importance. Hitherto we have been in the habit of referring to the period of youth as a matter of fact only important at all because some instincts of biological significance appear then. Now we see that youth probably exists for the sake of play. Animals can not be said to play because they are young and frolicsome, but rather they have a period of youth in order to play; for only by so doing can they supplement the insufficient hereditary endowment with individual experience, in view of the coming tasks of life. Of course this does not exclude other grounds, physiological ones, for instance, for the phenomenon of youth; but so far as concerns the fitting of the animal for his life duties, play is the most important one.
I may now briefly recapitulate. Our leading question seems to be as to the play of the young. That once adequately explained, the play of adults would present no special difficulties. The play of young animals has its origin in the fact that certain very important instincts appear at a time when the animal does not seri-
(76) -ously need them. This premature appearance can not be accounted for by inherited skill, because the inheritance of acquired characters is extremely doubtful. Even if such inheritance did have a part in it, the explanation by means of selection would still be most probable, since the utility of play is incalculable. This utility consists in the practice and exercise it affords for some of the more important duties of life, inasmuch as selection tends to weaken the blind force of instinct, and aids more and more the development of independent intelligence as a substitute for it. At the moment when intelligence is sufficiently evolved to be more useful in the struggle for life than the most perfect instinct, then will selection favour those individuals in whom the instincts in question appear earlier and in less elaborated forms-in forms that do not require serious motive, and are merely for purposes of practice and exercise-that is to say, it will favour those animals which play. Finally, in estimating the biological significance of play at its true worth, the thought was suggested that perhaps the very existence of youth is largely for the sake of play.
The animals do not play because they are young, but they have their youth because they must play.
But I must call attention to another important phenomenon that also has a direct relation to play, namely, the imitative impulse. It was remarked in the previous chapter that while imitation is not an essential feature of play, it is very often present. This is a suitable place to notice this important subject, which will constantly recur in the progress of our inquiry. First, it
(77) is very probable that imitation is itself instinctive. True, it is possible to conceive of the imitative impulse as of individual origin. Wundt teaches that every idea of movement presses to fulfil itself. (Many psychologists seek to reduce even the will to such ideas.) The notion of the movements seen in others is, of course, included, and this is the imitative impulse. But an origin so entirely individual and even accidental can hardly be attributed to an impulse of such enormous power. Wundt refers to the impulses, too, as hereditary phenomena, and, if I understand him aright, does not exclude imitation. Schneider thus expresses himself on the subject: " Wundt is quite right in regarding apperception of a movement idea, and the feelings connected with it as a direct impulse to make the movement. And the word idea is not used in a narrow sense, for even the perception of a movement awakens this impulse, and is the cause of many imitative movements." Schneider is, however, of the opinion that the development of this "intimate causal connection" rests in both cases on heredity (according to him, indeed, on the inheritance of acquired characters), and advances as an explanatory proof of this the fact that the imitative impulse is restricted to cases that are useful to the individual. "When a young lion sees a fish swimming or a bird flying he hardly feels a desire to swim or fly, while the old lion's movements when he observes them arouse the imitative impulse in him, because he is disposed to the movements by heredity. This is a proof that
(78) apperception should not be regarded as only a movement idea, for if that were all it is, animals, at least, would seek to imitate every motion they see, and we might expect to see a child at once begin a swaying motion on beholding a pendulum, instead of reaching for the ball of it, as it does."
Spencer also, James, and Stricker, regard the imitative impulse as an inherited instinct, and I think it is safe to trust these psychologists.
The imitative impulse is thus found to be an instinct directly useful in the serious work of life among most, and presumably among all, of the higher gregarious animals. Its simplest manifestation is the taking to flight of a whole herd as soon as one member shows fear. A more particular case is seen among certain domestic animals that blindly follow a leader- a fact well known to the crafty Panurge in Rabelais's grotesque romance, when during the voyage he wants to play a joke on the owner of a flock of sheep. This phenomenon, which may be explained by the principle of division of labour (for in this way one animal can watch for the whole
(79) flock), is also useful in advancing intellectual development, since selection favours young animals skilled in its use. So we have here an hereditary instinct that is even more especially adapted than that of play to render many other instincts unnecessary, and thus open the way for the development of intelligence along hereditary lines that can be turned to account for the attainment of qualities not inherited. Young animals, even some not gregarious, have an irresistible impulse to imitate any action of their parents, toward which their instinctive impulse is very weak, and they learn in this way what would never be developed in them individually without this imitative impulse. The examples cited from Wallace can be explained in this way. They do not argue against instinct, but rather show that many instincts are becoming rudimentary in the higher animals because they are being supplanted by another instinct-imitative impulse. And this substitution is of direct utility, for it furthers the development of intelligence. This reminds us of the teaching of Plato, that the ability to learn presupposes " reminiscence " from a previous existence. By means of imitation animals learn perfectly those things for which they have imperfect hereditary predispositions.
We then reach the following conclusion in our play inquiry-namely, that all youthful play is founded on instinct. These instincts are not so perfectly developed, not so stamped in all their details on the brain, as they would have to be if their first expressions were to be in serious acts. Therefore they appear in youth. and must be perfected during that period by constant practice. At the same time, where physical movements are concerned, the muscular system will also be developed by this exercise suitably for subsequent serious work-a result which would not be attained adequately with-
(80) -out play. In this way we can explain those plays referred to in this and the previous chapter, which can not be designated as imitative play, such as the gambolling of young creatures, their play with the organs of motion and speech, mock fighting, etc. Besides these plays, which are founded on strongly developed instincts, and can therefore be practised without a model, there are many others worthy of consideration: those in which at least two instincts are involved-one an impulse only rudimentarily present, though easily aroused, and the other the accompanying imitative instinct. To this class belong the instances already cited of young birds learning to sing, probably, too, the barking of puppies, and the imitative play of little girls whose motherly tending of their dolls could hardly reach the perfection in which we see it without imitation. It would be certainly hard to explain the choice of models by the different sexes without hereditary predisposition--why the boy's tin soldiers are his favourite toys, while the little girl is always the mother and housekeeper. Finally, it must be admitted that there are cases where the imitative impulse exceeds the limits of instinct and apparently works alone, as when apes imitate the actions of men, when parrots learn to speak intelligently, and when children play horse cars, railroad, hunter, teacher, and the like. But even here a latent desire to experiment contributes, and it is evident how necessary such play is to the development of mind and body.
We now have all the principles necessary for a psychology of play; only in outline, however. All refinements and expansions which may subsequently be brought to light, and which I may call idealizations of the bald play instinct, must be treated later. The following remarks will conclude this chapter:
Play is found among adult animals. A creature that once knows the pleasure of play will derive satisfaction from it even when youth is gone. And preservation of the species is advanced by exercise of the mind and body even in later years. I have a dog twelve years old that still shows a disposition to play now and then. We often see grown-up animals playfully roll over and over without any object, and many birds appear to sing from mere sportiveness without relation to courtship. Proof of this is difficult to substantiate, however. We do know that adult cats and dogs play, but in regard to other animals we can only speak of probabilities. If the playful character of some of the examples which I cite in the following chapters is not established beyond a doubt, I am consoled by a statement of Darwin's, made with great emphasis in The Descent of Man: " Nothing is more common than for animals to take pleasure in practising whatever instinct they follow at other times for some real good. How often do we see birds which fly easily, gliding and sailing through the air obviously for pleasure? The cat plays with the captured mouse and the cormorant with the captured fish. The weaver-bird when confined in a cage amuses itself by neatly weaving blades of grass between the wires of the cage. Birds which habitually fight during the breeding season are generally ready to fight at all times, and the males of the capercailzie sometimes hold their Balzen at the usual place of assemblage during the autumn. Hence. it is not, at all surprising that male birds should continue singing for their own amusement after the season for courtship is over."