I.—The Physiological Aspect

At the outset of our inquiry, we used the word “behaviour” in a wide and comprehensive sense. Thus broadly used, I said, the term in all cases indicates and draws attention to the reaction of that which we speak of as behaving in response to certain surrounding forces or circumstances which evoke the behaviour. The behaviour of living cells is dependent on changes in their environment; that of deciduous trees, as they put forth their leaves in the spring or shed them in the autumn, is related to the change of the season; instinctive, intelligent, and emotional behaviour are called forth in response to those circumstances which exercise a constraining influence at the moment of action. Used in this comprehensive sense, the term “behaviour” neither implies nor excludes the presence of consciousness. We know from our own experience, however, that consciousness does in some cases accompany behaviour, and we infer that in many other cases it may be present. But we need a criterion of its presence to guide our inferences, and this criterion we found in the ability of living beings to profit by experience. In Dr. Stout’s phraseology, if a thing seems to acquire meaning for such a being, and the behaviour is guided in accordance with such acquired meaning, we infer the presence of consciousness as supplying conditions effective in determining its course. Still this does not exclude, nay, rather it presupposes the presence of sentience at a lower stage of evolution, a sentience which is as yet ineffective since the process of conscious coalescence has not begun, or has not been carried far enough.

In foregoing chapters we have constantly held the problems of evolution in view, and in special sections directed attention to them. But the subject is so central to modern thought and discussion, that some further consideration of certain aspects of the evolutionary process and products will fitly serve to bring our inquiry to a conclusion.

We must accept, as a datum from the physiological point of view, the fact that protoplasm does respond to stimuli,—that it possesses the fundamental property of irritability. It is a substance that is in a state of unstable equilibrium. Its tendency to pass to a condition of more stable equilibrium is that in and through which organic behaviour in its very simplest expression is possible. And this, with progressive complication, runs through the whole gamut of animal behaviour, and eventually passes over into the sphere of consciousness. “The tendency to equilibrium,” writes Dr. Stout,[187] “is the physiological correlate of what on the psychical side we call conation,—the striving aspect of consciousness.” But, protoplasm at the outset—or as near the outset as we can get—is, in technical phrase, differentially responsive. The nature of the stimulus and the nature of the conditions decide what the nature of the response shall be. And even in that jelly-like speck of living matter, the Amoeba, the responses conspire to a biological end. If they did not so conspire, we should not have the phenomena of life. The mere act of living, building up from food-stuff and oxygen an unstable substance which “explodes” and contracts under stimulation, implies that the processes which thus conspire are related in such a manner as to fulfil and secure their end. In higher unicellular animals, such as the Paramecium, the relations are less simple; but in them the continuance of that sum of organic behaviour which we call life, is secured only on the condition that these less simple relations are duly preserved, and that the vital processes conspire with sufficient unity of biological purpose. And when we pass to the higher creatures in which many cells unite to form one animal, the very word “unite” indicates that the vital processes of all must conspire with sufficient unity of biological purpose to insure the continued life of the whole.

Now, in all the higher and more active animals a nervous system is developed, which has for its purpose and end the preservation and furtherance of unity amid circumstances of progressively increasing diversity. And in the course of its evolution an added means of preserving and furthering the essential unity is provided in consciousness, which, through the coalescence of scattered units of sentience, leads behaviour to acquire a new and higher unanimity of purpose. Thus a mental evolution is engrafted on the organic evolution which precedes it. But every step in this mental evolution presupposes a step in organic evolution. And such is the complexity of structure and process in all the higher animals that much of the business of behaviour is relegated to quasi-independent nervous centres, which perform this business automatically, and will continue to perform it, with much subsidiary unity of end, when they are left to themselves and all connection with the supremely unifying sensorium has been severed.

Before proceeding to give some examples of this fact, and to indicate its bearing on our interpretation of behaviour, it may be well to state distinctly that no attempt is or will be here made to trace in detail the course of the evolution of animal behaviour through the ascending grades of life, nor, indeed, to prove that there has been any such evolution. Evolution by natural genesis is here assumed as the only hypothesis with which science has any concern. If it be false, then have the labours of workers and thinkers, since Darwin and Mr. Herbert Spencer worked and thought, been vain. Special creation is not a scientific hypothesis, but a reference of biological and mental phenomena to an ultimate cause, which lies beyond and altogether apart from the scope of scientific inquiry. The fundamental assumption of the man of science is, that any natural event he may select for detailed study has natural conditions and antecedents. And it is only in such detailed study—taking this or that particular occurrence and endeavouring to ascertain what were its related antecedents—that advance in the evolutionary interpretation of nature can be secured.

Such advance has been secured by the labours of those physiologists who have established by careful experiment the quasi-independent action of subsidiary nerve-centres as constituents of the nervous system as a whole. In such animals as the crayfish and the lobster the central nervous system consists of a chain of “ganglia,” or nerve-knots, which are connected together by nerve-strands. If these strands be cut between the thorax, which carries the walking limbs, and the abdomen or hinder portion of the body, the nerve-connection between these parts is severed. If the forepart be irritated through its sense-organs, the limbs of that part will respond; but, whereas an unmutilated crayfish, subjected to such irritation, would give a vigorous flap of the tail, this does not take place in the crippled animal.[188] Still, if the abdomen be irritated, it will respond by a strong and swift contraction. The two portions of the body are each capable of acting independently with well co-ordinated movements, but no longer of working together with unity of purpose. In the hinder portion the abdominal limbs, or swimmerets, all swing backwards and forwards simultaneously with rhythmic strokes; they act in concert. Sever now the connections between their ganglia, and each pair of limbs will continue to swing rhythmically but not with concerted rhythm. We have isolated a number of quasi-independent centres, and rendered them really independent. Each is concerned with its own proper co-ordination, but can no longer combine with others in a wider co-ordination. Mr. Hyde[189] has shown that in the king-crab, Limulus, when the nerve-chain is severed just in front of the abdominal region, the rhythmic respiratory movements of the abdominal segments still proceed regularly and co-ordinately. Even when only a fraction of the nerve-cord, separated by severances in front and behind, is left, corresponding with a single abdominal segment, the rhythmic action of that segment continues; but it is no longer synchronous with that of adjacent segments similarly isolated.

It will probably not be contended that the co-ordinated rhythm of the isolated segment in crayfish or king-crab is anything but a bit of organic and physiological behaviour. Whether it be accompanied by consciousness—a bit of consciousness isolated from other bits—we do not know; but we have no grounds for supposing that the rhythmic behaviour is guided by consciousness. And when, as Dr. Carpenter pointed out half a century ago, a water-beetle, from which the “brain” has been removed, swims forwards if placed in water, we must surely regard the co-ordinated progression as organic behaviour, whatever view we may hold with regard to a consciousness which in such a case is in a very literal sense a divided consciousness.

In these invertebrates the central nervous system is obviously segmented—one can distinguish the ganglia and their connecting nerve-strands. In the vertebrate the brain and spinal cord form a continuous mass of nerve-tissue without obvious segmentation. But the pairs of spinal nerves, each nerve with its afferent and efferent “root,” indicate a really segmented condition, though in the cord itself the segments so run together and overlap that they cease to be externally obvious. And there is a certain, though limited, amount of overlap in the distribution of these segmental nerves. Still, well co-ordinated responses occur when comparatively short portions of the spinal cord are isolated by severance from the rest. In the male frog, especially during the breeding season, a clasping reflex is produced by stimulating the dark swollen pads on the inner side of the hand, and this, as Goltz has shown, is exhibited when all the central nervous system has been destroyed save the segments to which the nerves for the arms proceed. “Similarly,” writes Dr. Sherrington,[190] “in the cat and monkey, the reflex wagging of the tail persists when behind the spinal transection only the sacral region of the cord is left intact.” When the spinal cord of the dog is severed, so as to isolate that portion which is concerned with movements of the hinder part of the body, pressure on the pad of one hind-foot usually produces, not only a lifting of that leg, but also an extension of its fellow—that is to say, a co-ordinated response of the two limbs. But in the case of the vertebrates, more than in that of the invertebrates, the co-ordinated response of an isolated part of the central nervous system seems to lack the furtherance of its action, which normally comes from the higher centres from which it has been severed. “The spinal reflexes significant of progression seem,” says Dr. Sherrington,[191] “to contribute chiefly towards preparatory posture in readiness for the onset of action executed by the musculature under the driving of higher centres. Thus the well-known reflex spinal posture of the frog is flexion of the hind limbs, the extensors of the joints being taut and ready for the jump. The spinal reflexes, which in their results approximate most closely to the normal reactions of the unmutilated individual, are those connected with the pelvic and abdominal viscera,” many of which “are executed as spinal reflexes in a manner presenting little or no physiological defect from the normal. And if the bulb”—the continuation of the spinal cord within the skull to form the basal portion of the brain—“be included with the spinal cord, and these together, including their nerves, be isolated from the rest of the nervous system, the animal as regards its visceral life, including that of the heart and lungs, is practically intact.”

Huxley graphically describes the actions of a frog from which the cerebral hemispheres have been removed. “If that operation,” he says,[192] “is performed quickly and skilfully, the frog may be kept in a state of full bodily vigour for months, or it may be for years; but it will sit unmoved. It sees nothing; it hears nothing. It will starve sooner than feed itself, although food put into its mouth is swallowed. On irritation, it jumps or walks; if thrown into water it swims. If it be put on the hand it sits there, crouched, perfectly quiet, and would sit there for ever. If the hand be inclined very gently and slowly, so that the frog would naturally tend to slip off, the creature’s fore paws are shifted on to the edge of the hand, until he can just prevent himself from falling. If the turning of the hand be slowly continued, he mounts up with great care and deliberation, putting first one leg forward and then another, until he balances himself with perfect precision on the edge; and if the turning of the hand is continued, he goes through the needful set of muscular operations, until he comes to be seated in security on the back of the hand. The doing of all this requires a delicacy of co-ordination and a precision of adjustment of the muscular apparatus of the body which are only comparable to those of a rope-dancer.”

Now, why have we entered into these details? To reinforce, from a somewhat different point of view, that which has again and again been urged in the preceding sections of this inquiry, that much of animal behaviour is an organic legacy. A going mechanism of great delicacy, with ready-made co-ordinations, the products of biological evolution, affords to consciousness a vast body of its primary data. As Dr. Sherrington himself says,[193] “co-ordination is abundantly shown to result from the independent power of the spinal arcs, altogether apart from the influence of the great cranial sense-organs, and of the cerebral arcs superposed upon them. These senses and the brain find the elementary co-ordination of the skeletal musculature an achievement already provided and to hand in the spinal cord. And no doubt the product of the instrument is, with the instrument itself, given over to their use in the reactions they elicit from the spinal musculature.” We have seen how instinctive behaviour, in those animals in which it is best studied, affords in hereditary biological outline, a sketch which subsequent acquisition, under experience, serves only to elaborate by the filling in of details and of the more delicate shading in behaviour. But in the higher animals, in which a period of youth is a time for the acquisition of experience—for experimentation and practice,—it might seem that the inherited biological legacy was of less importance. The “spinal animal,” as Dr. Sherrington calls it,—that is, the animal in which the spinal centres are isolated from the cerebral centres—goes far to disprove any such view. In them the cerebral senses and the brain find elementary co-ordination of the bodily movements an achievement already provided and to hand in the spinal cord. But when different animals are compared—frog, bird, rabbit, dog, and monkey—the permanent effects of severance of brain connection, the effects which remain when the temporary period of disturbing “shock” is over, are more marked in the higher than the lower types. And concerning this, Dr. Sherrington says,[194] “The deeper depression of reaction into which the higher animal, as contrasted with the lower, sinks when made spinal, appears to me significant of this, that in the higher types, more than in the lower, the great cerebral senses actuate the motor organs, and impel the motions of the individual.”

Whether in the animal in which all direct connection between the anterior and posterior portions of the central nervous system has been severed there is a double consciousness—a cerebral consciousness and a spinal consciousness—we are not in a position accurately to determine. If the generally accepted opinion, that the higher brain-centres constitute the sensorium or seat of consciousness, be correct, we must suppose that a maimed consciousness, with many avenues of experience closed, is retained in the anterior moiety, while the posterior is relegated to a condition of mere sentience at best. In any case all relation between the two is prevented. The two—if two there be—are rendered quite independent through severance of the cord in the region of the neck. But there is a point of view indicated by Dr. Sherrington which is full of suggestion and interest.

“It is significant in the evolution of animal form,” he says,[195] “that the organ that exhibits most uninterrupted and harmonious increase in development, as studied successively in passing from lowest to highest, is the brain. And it is significant that in the nervous system—segmental system as it is—the brain is developed, not in those segments whose sense organs are ordinary cutaneous (tactual, etc.), muscular and visceral, but in the segments connected with the visual, olfactory, and auditory sense-organs; in other words, the brain is developed in the head. The head is, so to say, the individual; it has the mouth, it takes the food, including air and water, and it has the main sense organs providing data for both space and time. To this the body, an elongated motor organ with a share of the viscera and the skin, is appended primarily as a machine for locomotion. This latter must of necessity lie at the behest of the great sense organs of the head.”

Now let us try and picture to ourselves a spinal animal, or one which retains only the lowest portion of the brain, the part known as the bulb or medulla oblongata; let us assume that it is conscious and capable of acquiring experience through the association and coalescence of the data afforded by the senses that remain to it; and let us try to imagine the conscious situations which would arise, and their value in the guidance of behaviour. The senses that remain are touch and the temperature sense, the motor sense affording data from the muscles, joints, and tendons, and those which supply certain visceral sensations. There is not one of much, if any, guiding value left. There is not one of what we may term anticipatory use. There is not one which could serve to infuse anything like definite meaning into the situation. For, after all, meaning is expectation. There is an element of anticipation in all those senses which are of any real guiding value in the conscious situation. Sight, hearing, and, especially for some animals, smell,—these are the senses which forewarn of something which may follow; of other sensations with which in the course of experience they have coalesced. And they are all cut off from the supposed spinal animal. A light touch might in some cases forewarn of the shock or severe pressure, which would perhaps follow. But the shocks would so often come suddenly that it is questionable whether the warning would be of much avail. Still, touch is a warning and cognitive sense, and through it the environment would acquire a limited amount of meaning.

Now, the biological value of coalescent association lies in this very element of warning. The anticipatory senses, sight, hearing, smell, are in their several degrees the “projective” senses, the senses which carry with them the quantity of “outness.” And their “projective” character is the necessary psychological expression of their distinctive biological end. They must be projective, must carry with them “outness,” if they are to convey what we, following Dr. Stout, have so often spoken of as meaning. But if the biological value of coalescent association lies in the expectation it renders possible; and if, in the spinal animal, there are no senses left save touch, which could receive from the environment preparatory warning of what is coming; it would seem exceedingly improbable that it should develop quasi-independent conscious situations of its own. In the unmutilated animal, at any rate, tactual experience would most probably coalesce with that derived from the senses which more distinctively take the lead in the acquisition of meaning. And we may therefore, on these grounds, as well as on others, acquiesce in the current view that the quasi-independent functioning of the spinal cord and its constituent segments is, at best, lit up with those flashes of mere sentience of which Sir Michael Foster speaks in the passage we quoted in an earlier section.[196]

If from the consideration of the isolated spinal animal we turn for a moment to that of the isolated cerebral animal, we find it in a very different position. It is possessed of the warning senses—those which from several points of view are the leading senses—but they are leaders without a following; they have only a very limited company to conduct into action. The company is there, on the further side of the severance, but they have lost touch with it. They know not what it is doing, and have therefore neither the data nor the executive power to guide its manoeuvres in the field of behaviour. They can form maimed coalescent situations, but they are as impotent as a mere theorist devoid of all power of practical application. We need not, however, follow the theme further. We need only add that, could we isolate tracts of nervous tissue in the lower brain-centres of such a cerebral animal, we should find that subsidiary co-ordinations would belong, as a physiological heritage, to these isolated fragments.

The conclusions we may draw, then, with regard to the evolution of behaviour, as viewed in its physiological aspect, are that it is, in its simplest expression and in its most complex, conditioned by sufficient unity of purpose to meet the biological end of survival; that the complex unity of purpose may be analyzed into a multiplicity of subsidiary processes each with its subsidiary unity of purpose; and that the psychological coalescence which gives unity to experience under the guidance of the leading senses, is paralleled in a physiological coalescence within the nexus of the nervous system.

II.—The Biological Aspect

The biological aspect of behaviour—its relation to biological ends—has so often come under our consideration in the foregoing chapters that little need be added in this section: and that little may be most appropriately devoted, first to the question whether consciousness does influence behaviour; and secondly, this being accepted, to the importance of the rÔle that is played by the development of conscious situations in securing, in the higher animals, the biological end of racial preservation.

That this end is secured without the aid of consciousness in the case of many organic species, in all those, for example, which we classify as plants, must not be taken as presumptive evidence that in other species, for instance in the multitudinous host of insects, the development of conscious situations is of no biological value. The fact that chlorophyll is not developed in any mammal does not show that the possession of this substance is of no service to the higher plants. It would not be worth while to give expression to this very obvious truth, were it not that critics of natural selection persistently argue that because one species gets on perfectly well without this or that particular character it can have played no part in securing the survival of another species. When I described, at a meeting of naturalists, how well young chicks could swim, such a critic drew me aside after the meeting, and expressed his surprise that this did not convince me that the webbed foot of the duck could not logically be attributed to natural selection. This is an extreme case, and one obviously taken on peculiarly weak grounds. But even Huxley urged that, because a frog, from which the cerebral hemispheres have been removed, performs many co-ordinated actions without conscious guidance, consciousness is, throughout nature, merely an accompaniment of certain molecular changes in the brain. “Such a frog,” he says,[197] “walks, hops, swims, and goes through his gymnastic performances quite as well without consciousness, and consequently without volition, as with it; and if a frog, in his natural state, possesses anything corresponding with what we call volition, there is no reason to think that it is anything but a concomitant of the molecular changes in the brain which form part of the series involved in the production of motion.

“The consciousness of brutes,” he continues, “would appear to be related to the mechanism of their body simply as a collateral product of its working, and to be as completely without any power of modifying that working as the steam-whistle which accompanies the work of a locomotive engine is without influence on its machinery. Their volition, if they have any, is an emotion indicative of physical changes, not a cause of such changes. It does not enter into the chain of causation of their actions at all.”

If the literal truth of this contention—the logical soundness of this conclusion—be admitted, it seems absurd to speak of the biological value of consciousness in behaviour or to discuss the importance of the rÔle that is played by the development of conscious situations in securing the biological end of racial preservation.

Now, consciousness is regarded by an influential school of thinkers as a sort of deus ex machina, which, sitting enthroned, and crowned with a capital letter as Will, directs, like a being from another sphere, the doings of the body. It was against the doctrines of this school that Huxley took up arms. They do not concern us here. The will, or volition, as an underlying cause, stands outside the pale of scientific inquiry. It belongs to the wide realm of metaphysics; its plea must be heard in another court. In this part of his contention Huxley was, we believe, unquestionably right from the scientific standpoint. Neither will, nor impulse, nor instinct, nor consciousness itself, should be introduced into any scientific description or explanation of phenomena as a cause of their existence or being, for as such it does not enter into the sequence of events; it is that which metaphysics claims as their raison d’Être—that which gives them being. Science in this matter should be frankly agnostic—neither affirming nor denying aught. This, of course, is not equivalent to saying that the agnostic position is the true end of human reason. That would only be so on the assumption that the problems of science are the only problems with which that reason can deal. To exclude metaphysics from science is not to exclude it from human thought. As a matter of fact such exclusion is neither possible nor reasonable. But to clearly distinguish the problems of science from those of metaphysics is absolutely necessary, if we are to prevent hopeless confusion of issues.

In contending, however, against the introduction of metaphysical doctrines into the region of scientific explanation, Huxley seems to have been carried too far by the force of his own attack. So long as he held to the position that every conscious state has, as its concomitant, a molecular change in the brain, he had all the forces of evolution on his side. But when he said that consciousness is merely the steam-whistle of life’s locomotive, or merely answers to the sound which the animal-bell gives out when it is struck, he takes up another position of far less strategical strength. For whereas the frog from which the physical centres of consciousness have been removed sits crouched and motionless, and “will starve sooner than feed itself, although food put into its mouth is swallowed;” the frog in which conscious situations can take form in unmutilated cerebral hemispheres behaves in a very different manner. It is nothing less than pure assumption to say that the consciousness, which is admitted to be present, has practically no effect whatever upon the behaviour. And we must ask any evolutionist who accepts this conclusion, how he accounts on evolutionary grounds for the existence of a useless adjunct to neural processes.

“It is,” says Huxley,[198] “experimentally demonstrable—any one who cares to run a pin into himself may perform a sufficient demonstration of the fact—that a mode of motion of the nervous system is the immediate antecedent of a state of consciousness. We have as much reason for regarding the mode of motion as the cause of the state of consciousness, as we have for regarding any event as the cause of another. How the one phenomenon causes the other we know as much, or as little, as in any other case of causation; but we have as much right to believe that the sensation is an effect of the molecular change, as we have to believe that motion is an effect of impact; and there is as much propriety in saying that the brain evolves sensation, as there is in saying that an iron rod, when hammered, evolves heat.” But if we speak of the related antecedent as the cause, it is not obvious why we should not describe the desire to demonstrate the supposed fact as the cause of running in the pin. We seem to have just as much reason for calling this antecedent state of consciousness the cause of certain movements and behaviour, as of calling a mode of motion in the brain the cause of a further state of consciousness. It is true that we have not the least idea how the desire can cause the act; but Huxley practically admits that we have no idea how molecular change can be the cause of consciousness. In the one case we are no worse off than we are in the other. Neither position is logically defensible; since each assumes that physical events and states of consciousness can constitute links in the same causal chain.

The philosophical hypothesis known as monism regards the molecular change, not as the antecedent of a conscious state, but as its concomitant. That which from a physical and physiological point of view is a complex molecular disturbance is, at the same time, from a psychological point of view, a state of consciousness. The two are different aspects of one natural occurrence. Why such an occurrence should have two so different aspects we have not the faintest idea; but here we are not one whit worse off than we were before. The hypothesis does, however, help us to get over our difficulty. An essential feature of Huxley’s contention is that the physical and physiological chain of causation is complete in itself, which may be granted; and further, that if consciousness does arise it is merely an adjunct without influence on the sequence of events—what is influential is the molecular disturbance, not the consciousness which accompanies it. But according to monism the state of consciousness actually is that very same something which the physiologist calls, in the language of physics, a molecular disturbance. And in saying that consciousness influences behaviour one who accepts this hypothesis is merely avoiding a cumbrous form of circumlocution. He puts it in this way instead of saying that the nerve-changes in the cerebral hemispheres, or elsewhere, which from a psychological point of view are a conscious situation, influence and determine the course of behaviour. But from this point of view it is absurd to say that the consciousness is merely an adjunct—absurd to say that were there no conscious situation the neural situation would remain unchanged. They are the very same thing from different points of view; and to say there is no influential conscious situation is simply equivalent to saying that there is not this determining neural situation.

However we explain the fact, there are few who hesitate to accept it for the purposes of scientific explanation. The conscious situation, having no doubt for the physiologist a neural aspect if he could only get at it as a whole, does practically determine the behaviour of the animal which has gained the requisite experience. If we accept the fact, we may pass on to its importance in securing the biological end of race preservation.

It is a commonplace of evolutionary doctrine that, other things being equal, those races will survive, in the constituent members of which intelligent behaviour enables them to deal most effectually with an environment of increasing complexity. And it is a matter of familiar observation that such behaviour is closely connected with delicacy and refinement of development in those senses which take the lead in cognitional process, and with rapidity and precision in the motor co-ordination through which prompt and skilful advantage is taken of the situation which has, through experience, acquired meaning.

But though the importance of intelligent adjustment to the circumstances of life is widely admitted as a general principle, it is perhaps through a study of animal behaviour that we are best able to realize its full range and extent. Biologists are so largely, and quite wisely, occupied in the study of morphological and physiological problems, which admit of a treatment more exact than the most ardent advocate of the investigation of behaviour, under natural or even under experimental conditions, can claim; they devote, again quite rightly, so large a share of attention to the variation and natural selection of adaptive structure in its adult condition and embryonic stages; the pendulum of opinion has, under the teaching of Professor Weismann, swung so far in the direction of the non-acceptance of the hereditary transmission of characters individually acquired through intelligent adjustment or otherwise; that the part played by consciousness in the evolution of the higher and more active animals is apt to pass unnoticed or unrecorded. It is well, therefore, to put in a reminder that a great number of animals would never reach the adult state in which they pass into the hands of the comparative anatomist save for the acquisition of experience, and the effective use of the consciousness to which they are heirs; that their survival is due, not only to their possession of certain structures and organs, but, every whit as much, to the practical use to which these possessions are put in the give and take of active life; and that many interesting problems which are keenly discussed by evolutionists in the light of natural selection presuppose conscious situations which are more or less tacitly taken for granted.

Let us cast a rapid glance over some of these topics of biological discussion. The fascinating subject of mimicry, involving as it necessarily does the discussion of the value of warning colours and behaviour, a subject opening up an extensive group of problems so brilliantly studied by Professor Poulton, is meaningless save in so far as there is implied a conscious reaction to colour and form on the part of animals which can learn from experience. The warning colours reinstate a conscious situation, so that, misled by appearances, a bird mistakes the mimicking insect for its nauseous “model.”

The whole range of behaviour, included under play, experimentation, and practice, on the importance of which, following the lead so ably given by Professor Groos, we have insisted, is equally meaningless, save as a means to the acquisition of serviceable experience for use in the more serious business of after-life; and experience is the establishment, through association and coalescence, of conscious situations which possess guiding value. And if, as we shall hereafter see, they may also be regarded as a means of securing pleasure, as a psychological end of behaviour, it is not less obvious that it is only through the development of consciousness that such a psychological end can have any existence.

It matters not if the particular form assumed by play and experimentation be largely dependent on instinctive tendencies. For all the phenomena of instinct, profoundly organic as are the modes of behaviour comprised under this head, definite as are the inherited co-ordinations in the most typical examples of its occurrence, have also, except in some doubtful cases, a conscious aspect. At any rate this is the case in so far as instinctive response forms the hereditary basis on which is reared a more nicely adjusted intelligent edifice, in so far as instinctive procedure is subsequently modified and guided by acquired experience, in so far as there creeps in that “little dose of judgment” which Huber found in bees, Lord Avebury attributes to ants, Dr. Peckham sees in spiders and solitary wasps, and all observers find in birds and mammals. For if in these cases instinctive behaviour were unconscious, it would, as such, remain outside experience; and if outside experience, there could be no data on which consciousness could base any modification of inherited behaviour, no opportunity of taking up the ready-formed responses into the mental synthesis and utilizing them for the wider ends of intelligent purpose.

In social behaviour there is a reciprocity of suggestion between the members of the community. And such suggestion is operative through an appeal to consciousness. However instinctive the forms of procedure may be in social insects, there remains much beyond which is hard to explain on the hypothesis that there is, in them, nothing analogous to a conscious situation; while in such vertebrates as birds and mammals we cannot but believe that consciousness is the main determinant of much behaviour which seems to imply the germs, or more than the germs, of sympathy. The little monkey I saw in Hamburg cuddling up caressingly to a wounded companion, must surely have experienced a conscious situation analogous to that which prompts a child to nestle alongside her companion in distress. And he who has seen no signs of sympathy in dogs, has either watched their behaviour in vain, or is himself lacking in sympathy.

In sexual selection by preferential mating, even if we follow Professor Groos in believing that it is a special mode of natural selection, the conscious situation is essential. If we accept the theory in any form, we must regard the adornments, antics, and display of the male as an appeal in some way to the consciousness of the female, whatever particular form the effects in that consciousness may take, whether the appeal evoke a sense of beauty, or simply be a means of exciting to the consummation of the natural end of courtship. Even if we follow Mr. Wallace in regarding plume and song as “recognition marks,” it is only by their appeal to consciousness in this way, if in no other, that they are of any biological value. And this, of course, applies equally to the whole range of his theory of recognition marks—their sole utility lies in their being a stimulus to consciousness through which the end of recognition is secured. So, too, not only the specialized behaviour which we dignify by the name of “courtship,” but every case in which mate is drawn to mate through sight, smell, hearing—any of the leading senses—testifies to the importance of consciousness in furthering an end of supreme biological importance.

And if, as Darwin urged, the “law of battle” among the males co-operates with preferential mating, as we can hardly deny, in securing strong, vigorous, and healthy fathers of the generation they beget, here, too, consciousness is an important factor. Can we conceive a “law of battle” among unconscious beings? If success in the combat were a mere matter of brute strength, it would imply some consciousness in its dull exercise. But it is more. It is also a trial of skill. Were it not so our forefathers would not have spent hours in watching a cock-fight, or laid heavy odds on their particular “fancy.”

We need not labour the theme. In the search for food or a nesting site, in the capture of prey and escape from enemies, in all that demands attention, and in all that necessitates practice, in what M. Houssay calls “the industries of animals,” and in that which Mr. Hudson calls “tradition,” consciousness has a part to play. Even plants unconsciously appeal to the consciousness of insects, birds, and mammals. Their bright, scented, nectar-bearing flowers, and their sweet, coloured fruits are means of effecting the biological ends of fertilization and the dissemination of seeds, but only on condition that their colours stimulate the sense of sight, and their scent and sweetness the senses of smell and taste. It is, perhaps, going too far to claim that, wherever sense-organs exist they imply at least some dim and rudimentary form of conscious situation of guiding value so far as it goes; for it is possible that in some cases the coalescence of elementary items of sentience has not been carried far enough to justify us in speaking of experience by which the animal can profit. But it is surely not going too far to claim that, wherever two or three such sense-organs are gathered together in any living being, there is consciousness in the midst of them, beginning to exercise that guidance which serves so markedly to differentiate the typical animal from the typical plant.

But throughout the animal kingdom, until we reach its highest development in man, the guidance of consciousness, important as it is, seems to be almost wholly subservient to a biological end, that of the preservation of the race, and for the race of the individual. Practical utility is the touchstone of animal intelligence, and of the whole range of feeling and emotion in beings still under examination in the stern school of natural selection. By this we mean that practical utility has determined what degree and complexity of intelligence, feeling, and emotion shall be attained. If the requisite level be not attained—elimination. Higher levels no doubt bring advantage—so long as they are practically useful. But in the school of natural selection useless accomplishments are not much taught. Although its examinations are in a sense competitive, all are allowed to pass who qualify for survival. But the competitors become more numerous and the standard for a pass rises. As the school increases in size higher classes with harder problems to solve are established. Progress is an incident of the constant survival of the fittest when there are variations in fitness.

III.—The Psychological Aspect

On the hypothesis of monism, the nature of which, so far as it bears on our inquiry, was briefly indicated in the foregoing section, the conscious situation is the psychical or mental expression of that which for the physiologist is what we may term a neural situation. As such it does not enter into the chain of physical causation; nor do physical events as such—that is to say, save as experienced—enter into the chain of mental causation. For mental development they have no independent existence, and are negligible except in so far as they enter as items of experience into the conscious situation.

But altogether apart from the way or ways in which we may attempt to explain the fact, most of us believe, with unquestioning confidence, that the growth of practical experience, somehow associated with nervous changes in the brain or sensorium, is of real value in the guidance of behaviour in such manner as to secure biological ends. Conscious experience must therefore, in the animal world, serve its biological purpose, or it will be of no avail. If there be not a pre-established harmony, there must be an evolved harmony; and how such a harmony could be evolved if consciousness be not by some means in vital touch with behaviour, influenced by and in turn influencing it, we cannot conceive. The steam-whistle theory of consciousness leaves the matter, for the evolutionist, in this inconceivable position.

We need not, however, flog a dead horse. We need not ask how, on the steam-whistle theory, those states of feeling which we broadly classify as pleasurable could become associated with behaviour conducing to welfare, and those which we group as hurtful with behaviour which is biologically harmful. It is more important, again, to notice that, associated and consonant with the biological end, there arises a psychological end of behaviour—what we may term, with the qualifications before considered,[199] the getting of pleasure and the avoidance of pain. This is the purpose of behaviour as viewed from the psychological aspect. The biological end of animal conation is racial survival; its psychological end is individual satisfaction. And the two ends are, in the main and broadly speaking, consonant—a result which would unquestionably be secured by natural selection, but is on any other naturalistic hypothesis difficult of explanation.

But the two ends are not only consonant; they are supplementary one to the other. During much of the life of the higher animals there is no need, immediately present and pressing, for the output of action to meet biological ends. There are periods of life and intervals of time when the sharp incidence of the struggle for existence does not call for the serious business of behaviour. But at these periods and in these intervals the animal is not inactive; indeed, it is restless in its activity. Unless it be weary with unwonted exertion, or basking in the psychical sunshine of content, due to the unsought advent of pleasant stimulation or the after-effects of previous behaviour (for example, when hunger has been relieved), the healthy animal must be up and doing. This familiar fact no doubt affords the basis in observation of the surplus-energy theory of play. But is it necessarily surplus energy? Is it not rather normal energy which expends itself in this way when there is no immediate and serious biological business on hand? And, as Professor Groos has pointed out, play is seen when we have every reason to suppose there is no surplus energy, nay, even when the normal energy is at a low ebb. There is no more pathetic sight than a sick kitten, with energy obviously much below par, utilizing its little remaining strength in feeble attempts to play.

It is unnecessary to do more than remind the reader of the theory elaborated with so much skill and care by Professor Groos, that the forms assumed by play—in which, it will be remembered, he includes a very wide range of behaviour—have a very important indirect biological end in practice and experimentation. Our present point is, that its direct psychological end is the satisfaction it affords. Without this the individual would not be impelled to the continuance of performances which occupy a wide space in the field of animal behaviour in which the biological end has reference, not to present requirements, but to future needs.

No one has given better expression to the sway of this psychological end than Mr. W. H. Hudson. “We see,” he says,[200] “that the inferior animals, when the conditions of life are favourable, are subject to periodical fits of gladness, affecting them powerfully and standing out in vivid contrast to their ordinary temper. And we know what this feeling is—this periodic intense elation which even civilized man occasionally experiences when in perfect health, more especially when young. There are moments when he is mad with joy, when he cannot keep still, when his impulse is to sing and shout aloud and laugh at nothing, to run and leap and exert himself in some extravagant way. Among the heavier mammalians the feeling is manifested in loud noises, bellowings, and screamings, and in lumbering, uncouth motions—throwing up the heels, pretended panics, and ponderous mock battles.

“In smaller and livelier animals, with greater celerity and certitude in their motions, the feeling shows itself in more regular and often in more complex ways. Thus FelidÆ, when young, and in very agile sprightly species, like the puma, throughout life, simulate all the actions of an animal hunting its prey—sudden, intense excitement of discovery, concealment, gradual advance, masked by intervening objects, with intervals of watching, when they crouch motionless, the eyes flashing and tail waved from side to side; finally, the rush and spring, when the playfellow is captured, rolled over on his back, and worried to imaginary death. Other species of the most diverse kinds, in which voice is greatly developed, join in noisy concerts and choruses; many of the cats may be mentioned, also dogs and foxes, capybaras and other loquacious rodents; and in the howling monkeys this kind of performance rises to the sublime uproar of the tropical forest at eventide.

“Birds are more subject to this universal joyous instinct than mammals, and there are times when some species are constantly overflowing with it; and as they are so much freer than mammals, more buoyant and graceful in action, more loquacious, and have voices so much finer, their gladness shows itself in a greater variety of ways, with more regular and beautiful motions, and with melody. But every species or group of species has its own inherited form or style of performance; and however rude and irregular this may be, as in the case of the pretended stampedes and fights of wild cattle, that is the form in which the feeling will always be expressed.”

That all this, which Mr. Hudson so graphically describes, belongs to the psychological aspect of animal behaviour and is directly prompted by conative tendencies whose immediate end is conscious satisfaction, the mere joy of unrestrained and healthy activity, may be freely admitted, without denying that all this exuberant psychical life owes its evolution to the fact that it is in consonance with and supplemental to biological ends which secure survival. It is with animals as it is with man; play is the preparation for earnest. As I have elsewhere said,[201] what our national games have done for the English race it is difficult to overestimate. They train us to use our bodies and expend our energies to the best advantage. An old soldier, watching a football match, said, “That’s the training for our future soldiers and sailors.” The playing fields are the finest school of organized co-operation in the world. But, apart from compulsion, a boy will not enter into the game with that zest through which alone it acquires real value for training, unless there be an immediate psychological end in the satisfaction he derives. And with animals practice and preparation for the business of life could not occur if the ultimate biological purpose of it all were not supplemented by the enjoyment it brings for its own sake.

But in animal play, as indeed in that of human youth, we are perhaps a little apt, in laying stress on the bodily skill and readiness of response to which it so effectually ministers, to forget that it is also a psychological training. In technical phraseology, we are disposed to fix our attention on the acquired co-ordination of act and movement rather than on the correlation of conscious data, which renders possible the skilful performance. And yet, rightly considered, the behaviour itself is simply the outcome of a conscious situation, duly elaborated, and knit together through the association and coalescence of its constituent data. It is a means to the unification of consciousness by bringing into relation scattered and, at first, quasi-independent sensory and emotional elements. Success is only attained through the concentration of attention and effort on that which is the centre of interest and also the focus of endeavour. And this close attention and well-directed effort, which are trained in the playful output of energy, are just the mental qualities which will stand the animal in good stead when the real incidence of life’s struggle comes upon it, when the reward of success is survival and the penalty of failure elimination. For they are not merely physical qualities, though their effects are bodily movements of attack and defence, of active escape, or merely “lying low.” They are essential psychological features of a unified and well-directed conative process.

In the fairly abundant play-time of animal life, this unification and direction of conative process can take form under conditions wherein the preliminary failures which accompany all forms of learning do not entail the severe penalty of elimination. If we may so put it, and so apply a deeply instructive parable, Natural Selection says to her more favoured children, in which conscious situations can be developed, “Here are the talents with which I have endowed you; make use of them till I come, as come I shall in due time.” This animal puts them out to usury in play; that animal keeps them laid up in the napkin of inactivity. Then Natural Selection, the austere one, comes; gives the commendation of survival to the animal that had learnt to put its talents to use in the period of preparation, and condemns to elimination that which had not traded with his talents at the bank of play. In animal life, on the perceptual plane, we have the same need for training in little things and seemingly unimportant matters in preparation for the stress and storm which may, nay must, come upon them, that we find in men and women on the higher ethical plane. To those who think that the play of animals is too trifling a thing to affect the question of survival, we would suggest the application, with a necessary difference, of the thought which Miss Edith Simcox puts into the following words: “Does it,” she says, “seem a trifling thing to say that in the hours of passionate trial and temptation a man can have no better help than his own past? Every generous feeling that has not been crushed, every wholesome impulse that has been followed, every just perception, every habit of unselfish action, will be present in the background to guide or to sustain. It is too late, when the storm has burst, to provide our craft with rigging fit to weather it; but we may find a purpose for the years that oppress us by their dull calm, if we elect to spend them in laying up stores of strength and wisdom and emotional prejudices of a goodly human kind, whereby, if need arises, we may be able to resist hereafter the gusts of passion that might else bear us out of the straightforward course.” To apply the thought, the trifles of play supply the psychological rigging which alone can save the animal craft in the coming storm of the struggle for existence. And the point on which we have to lay special stress in this section is, that it is psychological rigging—or, if this seems to lay too much emphasis on the genesis of conscious situations, we may at least urge that the psychological ropes are of co-ordinate importance with the biological spars.

So far, then, we reach the following conclusion: that if we classify the behaviour of the higher and more intelligent animals under two heads, the one comprising all those acts which are of direct biological value in enabling the animal to escape elimination under the immediate stress of the struggle for existence, and the other including all those acts which are of indirect preparatory or educative value, the latter, which are under their biological aspect not less important than the former, are under their psychological aspect of perhaps even greater importance. For the conditions of actual struggle are not those under which mental development could most easily be furthered, though they are those in which it is most effectually tested. Hence, the more intelligent animals pass through a period during which they are more or less shielded from the incidence of natural selection by their parents, and this is the period of play and of psychological education. And the tendency to play is so far organic, in that it is dependent on inherited instinctive propensities, and so far psychological in that it is accompanied by a felt want, which constitutes a conative impulse finding its appropriate end in the consciousness of satisfaction. But play—if we accept the term as the group-name for all these modes of behaviour which fall under our second class, those of indirect biological value—does not cease with the period of youth; it occupies all the intervals in the more serious business of animal life. And no discussion of animal behaviour can be adequate which does not assign to this class its due place, alike in biological and in psychological evolution.

The whole value of experience lies in the linkage and coalescence of the data afforded to consciousness. It is true that an inherited nervous system supplies the organic conditions of that physiological linkage and functional coalescence of which experience is the psychological expression. It is true that this physical integration secures a ready-made grouping of the conscious data which are the concomitants of orderly molecular changes in the brain or analogous sensorium. Still, it also remains true that the value of experience lies in the further linkage and coalescence that is acquired by the individual in the course of what we may fitly call its education. Every step in this education gets its psychological sanction through the satisfaction it affords in consciousness; and the time of acquisition is not during the stress of examination in the actual struggle for existence, but rather in the youthful period and in the subsequent intervals of preparation and practice during the play-time of animal life.

The examination analogy—if, indeed, it may not be rightly regarded as something more than an analogy—may be pressed a little further as a means of fixing our attention on two points which are worthy of consideration. The first is that, in the preparation for the examination, specific practice as much of it is, cramming is not the system exemplified by the higher animals. A good all-round education in the acquisition of conscious situations more or less coalescent into a unified system of experience, and in their effective utilization without unnecessary delay and bungling along more or less converging lines of practical behaviour; this is what secures a “pass” in survival, especially where the circumstances of life have reached a considerable degree of complexity. The instinctive act, with its relatively definite response to a question which is almost certain to be set to every candidate for survival, is that, which is the analogue in behaviour to the result of a system of cram. Organic nature does employ this system in the lower classes of her school; definite responses are ground into merely instinctive types generation after generation, and the right answers are given, automatically and unintelligently, whenever the oft-recurrent questions are set. But this will not do when the questions require the exercise of intelligence, when they are of the nature of problems, with just those delicate but not unimportant shades of difference which baffle the candidate who has been drilled in a merely mechanical fashion. Hence the cramming of instinct does not suffice for animals whose environment presents problems of greater variety and greater complexity. Intelligence is required to meet the particular combinations as they arise. The greyhound, which is loosed on a hare, has never seen that hare run in exactly that way over that special tract of country. But he has been trained in such situations, and is thus prepared to meet the special problem in its details as they present themselves in the light of the experience he has gained of other like problems. And his skill in pursuit has not only been gained through education in coursing. In a thousand ways, as puppy and dog, he has learnt how to use well those sinewy limbs. The training of his whole life is brought to bear on the question immediately before him.

The general bearing of these facts is obvious. Play, as a means of animal education, is varied, and has for its end all-round training of the animal mind in its sphere of operation. Although there are some specific propensities, certain observable trends of behaviour, as in hunting-play, courtship-play, and the like, we must not expect, nor do we find, anything like stereotyped definiteness of conative activity. We find that freedom and elasticity in animal education which is, perhaps, more often advocated than carried into practice in human education.

The second point arising out of the examination analogy is, that its range determines the level of preparation therefor. It is, for animals, a practical examination, not a theoretical. Not a single question is set demanding an explanation. The problems are such as can be solved by intelligence, not such as require the exercise of reason, as we have used the term in foregoing pages. These higher problems are only set when the sixth form is reached, and there is no conclusive evidence that any animals get into the sixth. This, however, is entirely a question of evidence, and many of us will be glad to welcome them there, if proved ability to deal reflectively with ideational questions justifies their promotion.

If any of them do belong to this form, they have probably got there through play. For in the stress of the actual examination there is not much time for reflection. Or perhaps we may rather say that, not in actual struggle, and not in active preparation for it in play-time, but in intervals of leisure between both, when the animal lies quietly turning over in his mind we know not what, will experience be reviewed, and generalizations drawn as to the why of events in this strange world. Probably the animal accepts things as they are, and does not trouble about their explanation. But it may not be so. At any rate, if animals lack the means of descriptive inter-communication, and have no words as concrete pegs on which to hang abstract ideas, their explanations cannot be carried far. Theories without the power of disputation would be a poor solace in leisure moments.

One more point may be noticed with regard to the psychological aspect of the evolution of behaviour—the reciprocal action of intelligence. It is the intelligence of others that introduces so much variety and complexity into the environment. Hunters and hunted, combatants, rivals, mate and mate, enemies or companions in their varied aspects, introduce through their intelligence complications which only intelligence can meet. And, as intelligence begets intelligence, so do emotional attitudes beget answering emotional states. Psychological evolution translated into practical behaviour gives rise to situations of reciprocal complexity. This point of view is, however, so familiar, that nothing need be said in its further elucidation. The behaviour of any given animal does not stand alone, but is closely related with the behaviour of others. Among social animals the relationships are peculiarly close, and it is among them that the psychological aspect of behaviour reaches its highest expression.

IV.—Continuity in Evolution

Under the head of organic behaviour, in the widest acceptation of the term, fall the whole of physiology, the whole of embryological development, nay, more, the whole of organic evolution; while mental evolution, in all its stages, may be regarded as the psychological aspect of that which, from the physiological aspect, is the evolution of nervous systems. Life itself is the behaviour of a particular kind of substance which is found more or less abundantly under natural conditions. No other known substance behaves in this way, and so ignorant are we as to the conditions of its natural origin, that it is useless to guess at a scientific explanation. And even if we knew all the antecedents and conditions of its origin we should be no nearer a comprehension of why protoplasm has the peculiar properties which we find it to possess. That is a question to which science can give no answer. Who knows why a certain compound of oxygen and hydrogen in certain proportions has the properties of that which we call water?

Let us note the distinction between saying, as we said above, that life is the behaviour of protoplasm, and asserting that life is the cause of this behaviour. The one is a scientific statement of observed fact, the other an explanation of the fact in metaphysical terms, a reference of the fact to its underlying cause. So long as we quite clearly understand that we are talking the language of metaphysics, we may speak of life as a cause of organic behaviour; but let us be careful to remember that the statement has no more value for science than the assertion that aqueosity is the cause of the behaviour of water.

Leaving on one side, then, the natural origin of protoplasm, the conditions of which are unknown, we find that, as a matter of observation, every bit of living substance, the history of which has been traced, is a fragment detached from some other bit which behaved in the same way. This is the basal fact of the continuity of organic evolution. But such a detached fragment has the property of increasing by taking up from the environment more of those elementary materials from which it is itself compounded in subtle synthesis. Nay, further, every fragment of which we know the history is found to increase in such a way as to reach, in form, structure, and idiosyncracies of behaviour, the likeness of the organism—plant or animal—from which it was derived. In the higher plants and animals the separated fragments or cells are the ova and sperms, or their equivalents, which unite, with fusion or coalescence of their nuclear matter, and thus give rise to a new individual in the course of embryological development.

Now, as we have already seen, much modern biological discussion centres round the question whether the detached reproductive fragment, ovum or sperm as the case may be, is derived from the whole body of the parent, by what Darwin termed pangenesis or in some other way, or only from germinal substance set apart in development for this end. And we have provisionally accepted the hypothesis that it is the direct descendant of other reproductive cells; and that, throughout a long ancestry, stretching back into the far past, there never occurs in the direct line of genealogical sequence, any highly differentiated cell, such as a gland-cell, muscle-cell, nerve-cell; never, with certain reservations into which we need not enter, is found the representative of any tissue save that to which the reproductive function is restricted. In technical phraseology, the continuity of organic evolution is due to the continuity of the germinal substance.

During embryological development the fertilized ovum—consisting of two fused fragments of this germinal substance—gives rise to a host of ordered and marshalled cells, which are divisible into two groups: the one forms the body with its muscles, bones, glands, digestive system, skin, sense-organs, nerve-centres, and so forth; the other forms a reserve store of germinal substance, from which are derived the ova and sperms. The former take no direct share in reproduction; they are off the line of continuous descent; they die without issue. But they protect and minister to the reproductive function of the second group—the potential ancestors of the races to follow. But all instinctive and intelligent behaviour is the outcome of the orderly working of the nervous system, is initiated through sensory stimulation, and is executed by the motor organs; and all the structural parts, through which such behaviour is possible, belong to the body—that which dies without issue. How, then, can instinct and intelligence be inherited? In a sense they are not inherited. The nervous system which is their organic basis begets no heirs. But it is begotten of germinal substance, which not only produced the body of which the nervous system is a part, but also handed on, with that body, samples of the same germinal substance capable of reproducing a similar body and a like nervous system. Herein lies the basis of heredity.

The stress of the struggle for existence falls upon the body; and instinctive or intelligent behaviour is a means to its preservation in the struggle for existence. According as it survives or not, will the samples of germinal substance it contains fulfil their biological end or perish with it. Natural selection secures the survival of those animals which bear the seed from which their like will be developed.

On this view all variation arises within the germinal substance, but it is manifested in the body which is its product. How variations arise we do not know with any exactness of detail. That the germinal substance is influenced in its nutrition and in other ways by the surrounding tissues is highly probable; and this influence may lead to changes which are the source of variations; but it is very doubtful whether such influence can be what we before termed “homoeopathic.”[202] It is improbable that the formation of the nerve-connections involved in intelligent behaviour which has grown habitual through repetition, can so influence the germinal cells as to give rise to variations of like nature. In other words, acquired habit is probably not a direct determinant of an inherited variation of like nature in instinctive behaviour. Apart from such influence the only source of variations which can be assigned is either the differential division of nuclei in preparation for the process of fertilization,[203] or the process of fertilization itself. The union of perhaps differentiated germinal substance from two distinct parents affords the opportunities for the admixture and compounding of hereditary qualities in the two samples, from which variations favourable or the reverse may arise.

It is now generally recognized, however, that the origin of variations is a problem quite distinct from that of the survival of those whose direction is favourable to that end. The theory of natural selection, as such, does not pretend to offer any explanation of the manner in which variations arise; though of course a complete theory of organic evolution must assign the antecedents and conditions of organic progress in all its varied phases. We know that variations do occur; we know, too, that more individuals are born than survive to procreate their kind; and, on the theory of natural selection, we draw from these data the conclusion that, on the average, the animals that escape elimination are those in which the variations are of such a nature as to conduce to this end.

It will be seen that, on the hypothesis of organic heredity, thus briefly sketched, continuity can, in strictness and, as we may phrase it, in its first intent, only be predicated of the germinal substance; but that this substance gives rise to products—active vigorous animals behaving in certain ways, each after his kind—which hold similar germinal substance in trust for future use. Natural selection deals with the trustees; and if they succumb, that which they hold in trust is lost. To put the matter in another way: Nature says to the germinal substance, “By your products you must be judged in accordance with the criterion of utility and efficiency.” Practical use in the give and take of active life is the touchstone of all behaviour which makes for survival. This being secured, there may be a balance of behaviour for other purposes. But in animals the balance is not of large amount, and other purposes have not taken form and direction. It should be clearly noticed that, on the hypothesis we are considering, use is the test of survival, and though it is not the direct cause of variations, it affords their sanction in survival. That animal escapes elimination whose behaviour is of practical use; and it holds in trust for the future a store of germinal substance from which is produced a successor capable of behaving in like manner.

The whole drama of organic evolution may be regarded as the realization in a succession of individuals of the evolving potentiality of continuous lines of germinal substance. The successive individuals die—but the germinal substance lives on in their heirs, if they have any. In virtue of what intimate and hidden structure or disposition of parts the germ possesses this potentiality we do not know. The ovum of a dog is a microscopic speck less than one-hundredth of an inch in diameter; the sperm is far more minute. They unite, and their nuclei coalesce. The cellular product divides and subdivides. The cell colony absorbs nutriment from the maternal tissues. Division proceeds apace, and the cells are marshalled and ordered in embryological development; definite tissues are formed; the stages of their genesis can be predicted with accuracy; and in due time a puppy is born which shall grow to the likeness of its parents and behave as they behaved. We can trace the succession of events; we see that they form a related series; we have good reason for believing that the state of matters at any one moment is the antecedent condition of the state of matters at the succeeding moment. More than this science cannot say. The underlying cause is, for science, hidden in the mists of the unknown. Even for metaphysics it is but part of the force that beats through the universe and makes it not a chaos but a cosmos—a force known to us only in its effects.

It will thus be seen that the conception of continuity in organic evolution has, broadly considered, a threefold aspect. First, there is the continuity of the germinal substance through whose reproductive behaviour under the appropriate conditions embryological development occurs; secondly, there is continuity in this embryological development, stage by stage, from the fertilized ovum to the adult which is its final product and expression; thirdly, there is continuity in these final products, in the animals whose organic, instinctive, and intelligent behaviour lie open to our study and investigation. The first is germinal, the second developmental, the third evolutional continuity.

Before attempting to summarize some of the contributions afforded by our inquiry towards the doctrine of continuity in the last of these three aspects, we must pause for a moment to consider how far and in what sense continuity can be predicated of mental development.

We have regarded the conscious situation as the psychical aspect of a nerve-situation in the sensorium; and the nervous system, capable of behaving in this way, is in developmental continuity with the germinal substance of the fertilized ovum. But what shall we say with regard to the psychical aspect? Two hypotheses seem open to us, each of which presents difficulties, but of different kinds. The first is, that when the organic development of the nervous system reaches a certain level and order of complexity consciousness emerges, how and whence we know not. The second is, that consciousness is developed from sentience, which is the concomitant of all organic behaviour; which accompanies life wherever it occurs and therefore shares the continuity of the germinal substance.

The difficulty inseparable from the first hypothesis, is that it is contrary to the analogy of all that we know or infer elsewhere throughout the realm of nature. Huxley[204] likened its emergence to the production of heat when an iron bar is struck by repeated blows of the hammer. But this analogy will not hold; for heat is a mode of energy, and only emerges through the transformation of other and pre-existing modes of energy. A certain amount of the energy of motion in the massive hammer-head is transferred to the iron rod, and assumes the form of that molecular vibration which we call heat. And by what amount the one is the gainer, by that amount is the other the loser. But we have no reason to suppose that the like takes place in the origin of the mental concomitants of neural changes. No portion of the brain’s store of physical energy is drained off to form the rivulet of consciousness. Now, whenever we speak of a product elsewhere in nature, we mean a specialized bit of something pre-existent. Water is the product of pre-existing oxygen and hydrogen. Heat is the product of other forms of energy. But this is not so on the first hypothesis, according to which consciousness emerges when the functional activity of the nervous system reaches a certain level and order of complexity. The mental concomitants are not “products,” in the recognized sense of the term. Furthermore, although on this hypothesis we may still speak of what was termed above evolutional continuity in the mental concomitants, there is nothing analogous to either developmental or germinal continuity.

On the second hypothesis, according to which sentience is the concomitant of all organic behaviour, such developmental and germinal continuity, or their analogues in the psychical order of being, are rendered conceivable. Consciousness is regarded as a developed form of sentience. But the sentience is wholly hypothetical. It is at best a “may be,” and its existence is incapable of proof. And science is rightly impatient of hypotheses the validity of which cannot in any way be verified. Our safest course, therefore, is to accept that which is common to both hypotheses, evolutional continuity, and for the rest to be content with a confession of ignorance.

We have already drawn attention to the fact that mere sentience, if it exists, has no power of guidance over organic behaviour; but consciousness, when it emerges, is a concomitant of nervous processes which determine the nature and direction of such nerve-changes as are the antecedents of intelligent behaviour. The steps by which this control is established are unknown. It is, indeed, probable that conscious guidance arises as an accompaniment of the differentiation of controlling centres from the automatic centres of the nervous system; but of how this takes place we are as ignorant as we are of many other differentiations in the course of embryological development and evolutional progress. Of those nervous arrangements within the brain which are the physiological concomitants of the far later mental processes of reflection, abstraction, generalization, and the formation of ideals, we are, if it be possible, even yet more profoundly ignorant. Nor would it serve any good purpose to indulge in speculation where there are not even the data to enable us so much as to hazard a probable guess. The utmost we are justified in attempting is to show how organic behaviour leads up to and affords the requisite data for the exercise of intelligence, and how both supply the necessary preliminary stages in the development and evolution of what, following Dr. Stout, we have termed ideational process. This we have endeavoured to do in preceding pages; and all that is now required is to conclude our inquiry with a brief summary by which the results, as affording some basis for evolutional continuity, may be focussed.

We regard reflex action and instinctive behaviour, broadly considered, as genetically prior to that which is intelligent. Their development in the individual and their evolution in the race are reached by the differentiation and integration of nerve-centres. In the abdominal region of the crayfish, for example, special centres are differentiated for the behaviour of each pair of swimmerets; but these are so integrated that the whole series of like abdominal appendages swing rhythmically with co-ordinated movements. Now, when a sensorium is developed, it does not have to group by an act of conscious selection and deliberate arrangement the multiplicity of scattered sensory data which it receives; it does not have to organize from diverse and hitherto unrelated elements some sort of system in experience: it receives them as a physiological heritage already grouped, and to some extent organized. Stimulus and response are organically linked; and within the response inherited co-ordinations, often exceedingly complex, afford a correlated group of sensory data. Just in so far as organic heredity has provided a working system of bodily parts, does consciousness receive systematic information of their orderly working. No doubt it is true that the development and evolution of the sensorium proceeds pari passu with the development and evolution of reflex actions compounded and co-ordinated to give rise to instinctive behaviour. No doubt the progress of the one is in close touch and relation with the progress of the other; for such relation receives the emphatic sanction of utility. Still it is none the less true that in individual development, as in racial evolution, the organic takes the lead. What is intelligently acquired is something added to that which has been engrained, through natural selection or otherwise, as a potentiality of the germinal substance. What we have first to note, then, is that organic evolution provides ready-grouped data to consciousness.

The second point is, that the germs of abstraction and generalization, or rather processes which are the precursors of abstraction and generalization, arise, and cannot fail to arise, in the genesis of experience from the performance of inherited responses, and from the coalescence of their results into a conscious situation. To a quite young chick I gave pieces of yellow orange peel, which were found to be distasteful and rejected. In Dr. Stout’s phraseology, they acquired meaning in experience. Can one doubt that the colour and taste were thus rendered predominant, and that the shape, size, and other qualities of the bits of orange peel remained practically unnoticed? Shortly afterwards the chick was given chopped and crumbled egg; the fragments of “white” were eaten, but the bits of hard-boiled yolk were untouched. They possessed a sufficient general resemblance to the orange peel to carry the same meaning. In many ways particular qualities of objects are emphasized in so far as they incite to behaviour; they form centres of biological interest, just as the abstract quality of ideational thought is the centre of rational interest on a higher plane of mental development. And in many ways objects presenting certain salient features in common, amid differences which remain unnoticed, are unconsciously grouped as the starting-points of similar perceptual situations, just as in the generalization of ideational thought similar relationships are deliberately grouped as the starting-points of like conceptual situations. Both are purposive and have an end, which we as investigators are able to assign; but only for reflection and conceptual thought are they also purposeful—the end being foreseen and realized, not only by the investigators, but by the agent concerned. And the purpose or end itself is in the two cases different. In the one case it is the biological end of practical behaviour; in the other case it is the rational end of explanation—abstraction and generalization being deliberately used as a means to this latter end. The question has again and again been asked: Do animals reason? And different answers are given by those who are substantially in agreement as to the facts and their interpretation, but are not in agreement as to their use of the word “reason.” Perhaps, if the question assume the form—Are animals capable of explaining their own acts and the causes of phenomena?—the position of those who find the evidence of their doing so insufficient may be placed in a clearer light. This is what is generally meant by the statement that animals have probably not reached the level of rational beings.

But even if they have not reached this level, their perceptual processes supply the antecedent conditions which are necessary if this level is to be attained in the course of further evolution. We have seen that, even in relatively simple cases, where conscious situations mark only the beginnings of intelligence, there is a biological emphasis of some, rather than others, among what we call the qualities of objects, and there is a grouping, on biological grounds, of certain things which have some quality in common—such, for example, as being fit for food. Here we have at the outset of perceptual development the germs of processes which are the precursors of the abstraction and generalization of ideational thought. And in the more complex conscious situations of the higher animals these processes attain to such degree of development as is necessary to secure more difficult and more remote biological ends, until all that is necessary, for their rational use, is the quickening touch of a new purpose, that of explanation.

We have seen that, through what Dr. Stout terms “manipulation,” and Professor Groos “experimentation”—names applied to a type of behaviour widely exemplified among the higher animals,—things, as the nuclei of conscious situations, become differentiated from the environment. One can hardly question that a fly to the trout, a ball to the kitten, a bone to the puppy are things distinguished from their surroundings, and that they become marked off as special centres of interest. Here on the perceptual plane is a process which is the antecedent of the conception of quasi-independent objects on the ideational plane. For rational thought the thing, as object, is not only the centre of a practical situation leading to behaviour of direct or indirect biological value, but is the nucleus around which we build all the qualities which are ascertained by more elaborate manipulation and experimentation carried out deliberately and of set purpose for rational ends. It becomes capable of definition with the aim of explaining what are its characteristics as an object.

There can be little doubt that the higher animals become intimately and practically acquainted with their environment. The dog who accompanies his master in many a ramble, the horse who carries him again and again over all the surrounding country, has a good perceptual knowledge of a somewhat extended environment. And this, again, is the precursor of the far more extended conceptual knowledge which leads up at last to a rational conception of the universe of objects in their varied relationships. But only through the concentration of thought rendered possible by much true abstraction and generalization,—only through disentangling the relationships and regrouping them for the purpose of framing an ideal scheme,—only, in short, by explanation and for the sake of explanation is this difficult process brought to a more or less successful issue.

Again, there can be little doubt that the higher animals, in the course of experience begotten of behaviour, reach a perceptual sensing of the bodily self, through experience derived from the non-projecting senses, in pain and sickness, and often, we may hope, in the sense of well-being, and the joy of existence. They do not probably set this self in antithesis to the not-self. That comes with reflection, and is the result of ideal construction based on the analysis of experience, with a view to reaching some explanation of the genesis of experience. But in their perceptual awareness of the embodied self, they have that kind of consciousness which affords the necessary data, for the later conception of the self—when experience is polarized into its subjective and objective aspects and thus is explained, so far as science can explain it; suggesting, indeed, long ere science has attained this end, metaphysical explanations by reference to underlying causes—too often accepted as an easy substitute for the difficult tracing out of the antecedent conditions which science endeavours painfully and by slow steps to formulate.

It is unnecessary to do more than remind the reader that we have found that such processes as attention and imitation pass through instinctive and intelligent stages which are the precursors of the ideational stage, where they reach a higher expression as deliberately conscious acts. In the young bird that instinctively pecks at some small, perhaps moving, thing, which forms the starting point of a piece of responsive behaviour, we have attention in the germ. When experience has caused the thing to acquire meaning, attention passes into a succeeding intelligent phase; but only when we desire to explain this meaning, and attention thus has a deliberate purpose, do we find it entering upon its higher ideational career. So, too, as we have seen, imitation is at first a specialized form of instinctive behaviour, where the response is seen to resemble that which stimulates it. Later it becomes intelligent when the repetition of the imitative behaviour is due to the satisfaction it introduces into the conscious situation. Then, at last, it reaches the ideational stage, where reflection gives rise to an ideal, which is to be realized in conduct. The imitation by the child of its older companions is at first probably intelligent; but when the child begins to consider why it imitates these and not those among its companions, he is passing to the ideal stage, and imitation becomes the sincerest form of hero-worship. The boy who merely imitates his elder brothers playing at soldiers because he gets satisfaction from so doing, becomes the subaltern who has his ideal soldier, and will face death firmly rather than fall below his conception of how such a soldier should behave.

We need not again attempt to indicate how among animals we have the perceptual precursors of the Æsthetic and ethical concepts. But we may remind the reader that we endeavoured to show that intercommunication had its foundation in instinctive sounds; and that it passed into the intelligent stage in the perceptual life, when these sounds acquired meaning, and hence became guides to behaviour. This is especially instructive from our present standpoint, since it is probable that the passage of communication from the indicating to the descriptive stage afforded the conditions under which rational thought was evolved. For such thought it is essential that attention should be focussed on the relationships of things. And no description is possible without making distinctly present to consciousness these relationships, in time and space, the data for which are abundantly present in the perceptual life, though lurking in the background, and needing something to fix them and to aid consciousness in distinguishing them clearly. In descriptive communication parts of speech, or their initial equivalents, afford fixation points for these relationships, and serve to render them distinct. If the reader will try to describe even the simplest occurrence without introducing the symbols for the relations which the events bear to each other, his failure will serve to bring home how essential a feature this is. In social communication, then, we probably have the key to the passage from perceptual to ideational process; and in this passage description is the antecedent of, and affords the conditions to, explanation. Words, moreover, as we have already said, form the pegs upon which we can hang up, for ready reference, the products of abstraction and generalization, or, to modify the analogy, they form the bodies of which these products are the rational soul.

If we are ever to trace the passage from the instinctive through the indicating stage of communication, and so onwards through the beginnings of description to its higher levels, and thus to the use of language as a medium of explanation, it must be through child-study. In every normal human child the passage does actually take place, though, no doubt, in a condensed and abbreviated form as an epitomized recapitulation in individual development, of the steps of evolutional progress. Thus we may obtain a key to the solution of one of the most difficult problems in evolution by continuous process—that of the transition from animal behaviour to human conduct.