a.s.suming, then, the existence of instinctive action as above defined, it can be explained as -

I. A mere necessary consequence of bodily organisation. {92b}

II. A mechanism of brain or mind contrived by nature.

III. The outcome of an unconscious activity of mind.

In neither of the two first cases is there any scope for the idea of purpose; in the third, purpose must be present immediately before the action. In the two first cases, action is supposed to be brought about by means of an initial arrangement, either of bodily or mental mechanism, purpose being conceived of as existing on a single occasion only - that is to say, in the determination of the initial arrangement. In the third, purpose is conceived as present in every individual instance. Let us proceed to the consideration of these three cases.

Instinct is not a mere consequence of bodily organisation; for -

(a.) Bodies may be alike, yet they may be endowed with different instincts.

All spiders have the same spinning apparatus, but one kind weaves radiating webs, another irregular ones, while a third makes none at all, but lives in holes, whose walls it overspins, and whose entrance it closes with a door. Almost all birds have a like organisation for the construction of their nests (a beak and feet), but how infinitely do their nests vary in appearance, mode of construction, attachment to surrounding objects (they stand, are glued on, hang, &c.), selection of site (caves, holes, corners, forks of trees, shrubs, the ground), and excellence of workmanship; how often, too, are they not varied in the species of a single genus, as of parus. Many birds, moreover, build no nest at all. The difference in the songs of birds are in like manner independent of the special construction of their voice apparatus, nor do the modes of nest construction that obtain among ants and bees depend upon their bodily organisation. Organisation, as a general rule, only renders the bird capable of singing, as giving it an apparatus with which to sing at all, but it has nothing to do with the specific character of the execution ... The nursing, defence, and education of offspring cannot be considered as in any way more dependent upon bodily organisation; nor yet the sites which insects choose for the laying of their eggs; nor, again, the selection of deposits of sp.a.w.n, of their own species, by male fish for impregnation. The rabbit burrows, the hare does not, though both have the same burrowing apparatus. The hare, however, has less need of a subterranean place of refuge by reason of its greater swiftness. Some birds, with excellent powers of flight, are nevertheless stationary in their habits, as the secretary falcon and certain other birds of prey; while even such moderate fliers as quails are sometimes known to make very distant migrations.

(b.) Like instincts may be found a.s.sociated with unlike organs.

Birds with and without feet adapted for climbing live in trees; so also do monkeys with and without flexible tails, squirrels, sloths, pumas, &c. Mole-crickets dig with a well-p.r.o.nounced spade upon their fore-feet, while the burying-beetle does the same thing though it has no special apparatus whatever. The mole conveys its winter provender in pockets, an inch wide, long and half an inch wide within its cheeks; the field-mouse does so without the help of any such contrivance. The migratory instinct displays itself with equal strength in animals of widely different form, by whatever means they may pursue their journey, whether by water, land, or air.

It is clear, therefore, that instinct is in great measure independent of bodily organisation. Granted, indeed, that a certain amount of bodily apparatus is a sine qua non for any power of execution at all - as, for example, that there would be no ingenious nest without organs more or less adapted for its construction, no spinning of a web without spinning glands - nevertheless, it is impossible to maintain that instinct is a consequence of organisation. The mere existence of the organ does not const.i.tute even the smallest incentive to any corresponding habitual activity. A sensation of pleasure must at least accompany the use of the organ before its existence can incite to its employment. And even so when a sensation of pleasure has given the impulse which is to render it active, it is only the fact of there being activity at all, and not the special characteristics of the activity, that can be due to organisation. The reason for the special mode of the activity is the very problem that we have to solve. No one will call the action of the spider instinctive in voiding the fluid from her spinning gland when it is too full, and therefore painful to her; nor that of the male fish when it does what amounts to much the same thing as this. The instinct and the marvel lie in the fact that the spider spins threads, and proceeds to weave her web with them, and that the male fish will only impregnate ova of his own species.

Another proof that the pleasure felt in the employment of an organ is wholly inadequate to account for this employment is to be found in the fact that the moral greatness of instinct, the point in respect of which it most commands our admiration, consists in the obedience paid to its behests, to the postponement of all personal well-being, and at the cost, it may be, of life itself. If the mere pleasure of relieving certain glands from overfulness were the reason why caterpillars generally spin webs, they would go on spinning until they had relieved these glands, but they would not repair their work as often as any one destroyed it, and do this again and again until they die of exhaustion. The same holds good with the other instincts that at first sight appear to be inspired only by a sensation of pleasure; for if we change the circ.u.mstances, so as to put self-sacrifice in the place of self-interest, it becomes at once apparent that they have a higher source than this. We think, for example, that birds pair for the sake of mere s.e.xual gratification; why, then, do they leave off pairing as soon as they have laid the requisite number of eggs? That there is a reproductive instinct over and above the desire for s.e.xual gratification appears from the fact that if a man takes an egg out of the nest, the birds will come together again and the hen will lay another egg; or, if they belong to some of the more wary species, they will desert their nest, and make preparation for an entirely new brood. A female wryneck, whose nest was daily robbed of the egg she laid in it, continued to lay a new one, which grew smaller and smaller, till, when she had laid her twenty-ninth egg, she was found dead upon her nest. If an instinct cannot stand the test of self-sacrifice - if it is the simple outcome of a desire for bodily gratification - then it is no true instinct, and is only so called erroneously.

Instinct is not a mechanism of brain or mind implanted in living beings by nature; for, if it were, then instinctive action without any, even unconscious, activity of mind, and with no conception concerning the purpose of the action, would be executed mechanically, the purpose having been once for all thought out by Nature or Providence, which has so organised the individual that it acts henceforth as a purely mechanical medium. We are now dealing with a psychical organisation as the cause instinct, as we were above dealing with a physical. psychical organisation would be a conceivable explanation and we need look no farther if every instinct once belonging to an animal discharged its functions in an unvarying manner. But this is never found to be the case, for instincts vary when there arises a sufficient motive for varying them. This proves that special exterior circ.u.mstances enter into the matter, and that these circ.u.mstances are the very things that render the attainment of the purpose possible through means selected by the instinct. Here first do we find instinct acting as though it were actually design with action following at its heels, for until the arrival of the motive, the instinct remains late and discharges no function whatever. The motive enters by way of an idea received into the mind through the instrumentality of the senses, and there is a constant connection between instinct in action and all sensual images which give information that an opportunity has arisen for attaining the ends proposed to itself by the instinct.

The psychical mechanism of this constant connection must also be looked for. It may help us here to turn to the piano for an ill.u.s.tration. The struck keys are the motives, the notes that sound in consequence are the instincts in action. This ill.u.s.tration might perhaps be allowed to pa.s.s (if we also suppose that entirely different keys can give out the same sound) if instincts could only be compared with distinctly tuned notes, so that one and the same instinct acted always in the same manner on the rising of the motive which should set it in action. This, however, is not so; for it is the blind unconscious purpose of the instinct that is alone constant, the instinct itself - that is to say, the will to make use of certain means - varying as the means that can be most suitably employed vary under varying circ.u.mstances.

In this we condemn the theory which refuses to recognise unconscious purpose as present in each individual case of instinctive action. For he who maintains instinct to be the result of a mechanism of mind, must suppose a special and constant mechanism for each variation and modification of the instinct in accordance with exterior circ.u.mstances, {97} that is to say, a new string giving a note with a new tone must be inserted, and this would involve the mechanism in endless complication. But the fact that the purpose is constant notwithstanding all manner of variation in the means chosen by the instinct, proves that there is no necessity for the supposition of such an elaborate mental mechanism - the presence of an unconscious purpose being sufficient to explain the facts. The purpose of the bird, for example, that has laid her eggs is constant, and consists in the desire to bring her young to maturity. When the temperature of the air is insufficient to effect this, she sits upon her eggs, and only intermits her sittings in the warmest countries; the mammal, on the other hand, attains the fulfilment of its instinctive purpose without any co-operation on its own part. In warm climates many birds only sit by night, and small exotic birds that have built in aviaries kept at a high temperature sit little upon their eggs or not at all. How inconceivable is the supposition of a mechanism that impels the bird to sit as soon as the temperature falls below a certain height! How clear and simple, on the other hand, is the view that there is an unconscious purpose constraining the volition of the bird to the use of the fitting means, of which process, however, only the last link, that is to say, the will immediately preceding the action falls within the consciousness of the bird!

In South Africa the sparrow surrounds her nest with thorns as a defence against apes and serpents. The eggs of the cuckoo, as regards size, colour, and marking, invariably resemble those of the birds in whose nests she lays. Sylvia ruja, for example, lays a white egg with violet spots; Sylvia hippolais, a red one with black spots; Regulus ignicapellus, a cloudy red; but the cuckoo's egg is in each case so deceptive an imitation of its model, that it can hardly be distinguished except by the structure of its sh.e.l.l.

Huber contrived that his bees should be unable to build in their usual instinctive manner, beginning from above and working downwards; on this they began building from below, and again horizontally. The outermost cells that spring from the top of the hive or abut against its sides are not hexagonal, but pentagonal, so as to gain in strength, being attached with one base instead of two sides. In autumn bees lengthen their existing honey cells if these are insufficient, but in the ensuing spring they again shorten them in order to get greater roadway between the combs. When the full combs have become too heavy, they strengthen the walls of the uppermost or bearing cells by thickening them with wax and propolis. If larvae of working bees are introduced into the cells set apart for drones, the working bees will cover these cells with the flat lids usual for this kind of larvae, and not with the round ones that are proper for drones. In autumn, as a general rule, bees kill their drones, but they refrain from doing this when they have lost their queen, and keep them to fertilise the young queen, who will be developed from larvae that would otherwise have become working bees. Huber observed that they defend the entrance of their hive against the inroads of the sphinx moth by means of skilful constructions made of wax and propolis. They only introduce propolis when they want it for the execution of repairs, or for some other special purpose. Spiders and caterpillars also display marvellous dexterity in the repair of their webs if they have been damaged, and this requires powers perfectly distinct from those requisite for the construction of a new one.

The above examples might be multiplied indefinitely, but they are sufficient to establish the fact that instincts are not capacities rolled, as it were, off a reel mechanically, according to an invariable system, but that they adapt themselves most closely to the circ.u.mstances of each case, and are capable of such great modification and variation that at times they almost appear to cease to be instinctive.

Many will, indeed, ascribe these modifications to conscious deliberation on the part of the animals themselves, and it is impossible to deny that in the case of the more intellectually gifted animals there may be such a thing as a combination of instinctive faculty and conscious reflection. I think, however, the examples already cited are enough to show that often where the normal and the abnormal action springs from the same source, without any complication with conscious deliberation, they are either both instinctive or both deliberative. {99} Or is that which prompts the bee to build hexagonal prisms in the middle of her comb something of an actually distinct character from that which impels her to build pentagonal ones at the sides? Are there two separate kinds of thing, one of which induces birds under certain circ.u.mstances to sit upon their eggs, while another leads them under certain other circ.u.mstances to refrain from doing so? And does this hold good also with bees when they at one time kill their brethren without mercy and at another grant them their lives? Or with birds when they construct the kind of nest peculiar to their race, and, again, any special provision which they may think fit under certain circ.u.mstances to take? If it is once granted that the normal and the abnormal manifestations of instinct - and they are often incapable of being distinguished - spring from a single source, then the objection that the modification is due to conscious knowledge will be found to be a suicidal one later on, so far as it is directed against instinct generally. It may be sufficient here to point out, in antic.i.p.ation of remarks that will be found in later chapters, that instinct and the power of organic development involve the same essential principle, though operating under different circ.u.mstances - the two melting into one another without any definite boundary between them. Here, then, we have conclusive proof that instinct does not depend upon organisation of body or brain, but that, more truly, the organisation is due to the nature and manner of the instinct.

On the other hand, we must now return to a closer consideration of the conception of a psychical mechanism. {100} And here we find that this mechanism, in spite of its explaining so much, is itself so obscure that we can hardly form any idea concerning it. The motive enters the mind by way of a conscious sensual impression; this is the first link of the process; the last link {101} appears as the conscious motive of an action. Both, however, are entirely unlike, and neither has anything to do with ordinary motivation, which consists exclusively in the desire that springs from a conception either of pleasure or dislike - the former prompting to the attainment of any object, the latter to its avoidance. In the case of instinct, pleasure is for the most part a concomitant phenomenon; but it is not so always, as we have already seen, inasmuch as the consummation and highest moral development of instinct displays itself in self-sacrifice.

The true problem, however, lies far deeper than this. For every conception of a pleasure proves that we have experienced this pleasure already. But it follows from this, that when the pleasure was first felt there must have been will present, in the gratification of which will the pleasure consisted; the question, therefore, arises, whence did the will come before the pleasure that would follow on its gratification was known, and before bodily pain, as, for example, of hunger, rendered relief imperative? Yet we may see that even though an animal has grown up apart from any others of its kind, it will yet none the less manifest the instinctive impulses of its race, though experience can have taught it nothing whatever concerning the pleasure that will ensue upon their gratification. As regards instinct, therefore, there must be a causal connection between the motivating sensual conception and the will to perform the instinctive action, and the pleasure of the subsequent gratification has nothing to do with the matter. We know by the experience of our own instincts that this causal connection does not lie within our consciousness; {102a} therefore, if it is to be a mechanism of any kind, it can only be either an unconscious mechanical induction and metamorphosis of the vibrations of the conceived motive into the vibrations of the conscious action in the brain, or an unconscious spiritual mechanism.

In the first case, it is surely strange that this process should go on unconsciously, though it is so powerful in its effects that the will resulting from it overpowers every other consideration, every other kind of will, and that vibrations of this kind, when set up in the brain, become always consciously perceived; nor is it easy to conceive in what way this metamorphosis can take place so that the constant purpose can be attained under varying circ.u.mstances by the resulting will in modes that vary with variation of the special features of each individual case.

But if we take the other alternative, and suppose an unconscious mental mechanism, we cannot legitimately conceive of the process going on in this as other than what prevails in all mental mechanism, namely, than as by way of idea and will. We are, therefore, compelled to imagine a causal connection between the consciously recognised motive and the will to do the instinctive action, through unconscious idea and will; nor do I know how this connection can be conceived as being brought about more simply than through a conceived and willed purpose. {102b} Arrived at this point, however, we have attained the logical mechanism peculiar to and inseparable from all mind, and find unconscious purpose to be an indispensable link in every instinctive action. With this, therefore, the conception of a mental mechanism, dead and predestined from without, has disappeared, and has become transformed into the spiritual life inseparable from logic, so that we have reached the sole remaining requirement for the conception of an actual instinct, which proves to be a conscious willing of the means towards an unconsciously willed purpose. This conception explains clearly and without violence all the problems which instinct presents to us; or more truly, all that was problematical about instinct disappears when its true nature has been thus declared. If this work were confined to the consideration of instinct alone, the conception of an unconscious activity of mind might excite opposition, inasmuch as it is one with which our educated public is not yet familiar; but in a work like the present, every chapter of which adduces fresh facts in support of the existence of such an activity and of its remarkable consequences, the novelty of the theory should be taken no farther into consideration.

Though I so confidently deny that instinct is the simple action of a mechanism which has been contrived once for all, I by no means exclude the supposition that in the const.i.tution of the brain, the ganglia, and the whole body, in respect of morphological as well as molecular-physiological condition, certain predispositions can be established which direct the unconscious intermediaries more readily into one channel than into another. This predisposition is either the result of a habit which keeps continually cutting for itself a deeper and deeper channel, until in the end it leaves indelible traces whether in the individual or in the race, or it is expressly called into being by the unconscious formative principle in generation, so as to facilitate action in a given direction. This last will be the case more frequently in respect of exterior organisation - as, for example, with the weapons or working organs of animals - while to the former must be referred the molecular condition of brain and ganglia which bring about the perpetually recurring elements of an instinct such as the hexagonal shape of the cells of bees. We shall presently see that by individual character we mean the sum of the individual methods of reaction against all possible motives, and that this character depends essentially upon a const.i.tution of mind and body acquired in some measure through habit by the individual, but for the most part inherited. But an instinct is also a mode of reaction against certain motives; here, too, then, we are dealing with character, though perhaps not so much with that of the individual as of the race; for by character in regard to instinct we do not intend the differences that distinguish individuals, but races from one another. If any one chooses to maintain that such a predisposition for certain kinds of activity on the part of brain and body const.i.tutes a mechanism, this may in one sense be admitted; but as against this view it must be remarked -

1. That such deviations from the normal scheme of an instinct as cannot be referred to conscious deliberation are not provided for by any predisposition in this mechanism.

2. That heredity is only possible under the circ.u.mstances of a constant superintendence of the embryonic development by a purposive unconscious activity of growth. It must be admitted, however, that this is influenced in return by the predisposition existing in the germ.

3. That the impressing of the predisposition upon the individual from whom it is inherited can only be effected by long practice, consequently the instinct without auxiliary mechanism {105a} is the originating cause of the auxiliary mechanism.

4. That none of those instinctive actions that are performed rarely, or perhaps once only, in the lifetime of any individual - as, for example, those connected with the propagation and metamorphoses of the lower forms of life, and none of those instinctive omissions of action, neglect of which necessarily entails death - can be conceived as having become engrained into the character through habit; the ganglionic const.i.tution, therefore, that predisposes the animal towards them must have been fashioned purposively.

5. That even the presence of an auxiliary mechanism {105b} does not compel the unconscious to a particular corresponding mode of instinctive action, but only predisposes it. This is shown by the possibility of departure from the normal type of action, so that the unconscious purpose is always stronger than the ganglionic const.i.tution, and takes any opportunity of choosing from several similar possible courses the one that is handiest and most convenient to the const.i.tution of the individual.

We now approach the question that I have reserved for our final one, - Is there, namely, actually such a thing as instinct, {105c} or are all so-called instinctive actions only the results of conscious deliberation?

In support of the second of these two views, it may be alleged that the more limited is the range of the conscious mental activity of any living being, the more fully developed in proportion to its entire mental power is its performance commonly found to be in respect of its own limited and special instinctive department. This holds as good with the lower animals as with men, and is explained by the fact that perfection of proficiency is only partly dependent upon natural capacity, but is in great measure due to practice and cultivation of the original faculty. A philologist, for example, is unskilled in questions of jurisprudence; a natural philosopher or mathematician, in philology; an abstract philosopher, in poetical criticism. Nor has this anything to do with the natural talents of the several persons, but follows as a consequence of their special training. The more special, therefore, is the direction in which the mental activity of any living being is exercised, the more will the whole developing and practising power of the mind be brought to bear upon this one branch, so that it is not surprising if the special power comes ultimately to bear an increased proportion to the total power of the individual, through the contraction of the range within which it is exercised.

Those, however, who apply this to the elucidation of instinct should not forget the words, "in proportion to the entire mental power of the animal in question," and should bear in mind that the entire mental power becomes less and less continually as we descend the scale of animal life, whereas proficiency in the performance of an instinctive action seems to be much of a muchness in all grades of the animal world. As, therefore, those performances which indisputably proceed from conscious deliberation decrease proportionately with decrease of mental power, while nothing of the kind is observable in the case of instinct - it follows that instinct must involve some other principle than that of conscious intelligence. We see, moreover, that actions which have their source in conscious intelligence are of one and the same kind, whether among the lower animals or with mankind - that is to say, that they are acquired by apprenticeship or instruction and perfected by practice; so that the saying, "Age brings wisdom," holds good with the brutes as much as with ourselves. Instinctive actions, on the contrary, have a special and distinct character, in that they are performed with no less proficiency by animals that have been reared in solitude than by those that have been instructed by their parents, the first essays of a hitherto unpractised animal being as successful as its later ones. There is a difference in principle here which cannot be mistaken. Again, we know by experience that the feebler and more limited an intelligence is, the more slowly do ideas act upon it, that is to say, the slower and more laborious is its conscious thought. So long as instinct does not come into play, this holds good both in the case of men of different powers of comprehension and with animals; but with instinct all is changed, for it is the speciality of instinct never to hesitate or loiter, but to take action instantly upon perceiving that the stimulating motive has made its appearance. This rapidity in arriving at a resolution is common to the instinctive actions both of the highest and the lowest animals, and indicates an essential difference between instinct and conscious deliberation.

Finally, as regards perfection of the power of execution, a glance will suffice to show the disproportion that exists between this and the grade of intellectual activity on which an animal may be standing. Take, for instance, the caterpillar of the emperor moth (Saturnia pavonia minor). It eats the leaves of the bush upon which it was born; at the utmost has just enough sense to get on to the lower sides of the leaves if it begins to rain, and from time to time changes its skin. This is its whole existence, which certainly does not lead us to expect a display of any, even the most limited, intellectual power. When, however, the time comes for the larva of this moth to become a chrysalis, it spins for itself a double coc.o.o.n, fortified with bristles that point outwards, so that it can be opened easily from within, though it is sufficiently impenetrable from without. If this contrivance were the result of conscious reflection, we should have to suppose some such reasoning process as the following to take place in the mind of the caterpillar:- "I am about to become a chrysalis, and, motionless as I must be, shall be exposed to many different kinds of attack. I must therefore weave myself a web. But when I am a moth I shall not be able, as some moths are, to find my way out of it by chemical or mechanical means; therefore I must leave a way open for myself. In order, however, that my enemies may not take advantage of this, I will close it with elastic bristles, which I can easily push asunder from within, but which, upon the principle of the arch, will resist all pressure from without." Surely this is asking rather too much from a poor caterpillar; yet the whole of the foregoing must be thought out if a correct result is to be arrived at.

This theoretical separation of instinct from conscious intelligence can be easily misrepresented by opponents of my theory, as though a separation in practice also would be necessitated in consequence. This is by no means my intention. On the contrary, I have already insisted at some length that both the two kinds of mental activity may co-exist in all manner of different proportions, so that there may be every degree of combination, from pure instinct to pure deliberation. We shall see, however, in a later chapter, that even in the highest and most abstract activity of human consciousness there are forces at work that are of the highest importance, and are essentially of the same kind as instinct.

On the other hand, the most marvellous displays of instinct are to be found not only in plants, but also in those lowest organisms of the simplest bodily form which are partly unicellular, and in respect of conscious intelligence stand far below the higher plants - to which, indeed, any kind of deliberative faculty is commonly denied. Even in the case of those minute microscopic organisms that baffle our attempts to cla.s.sify them either as animals or vegetables, we are still compelled to admire an instinctive, purposive behaviour, which goes far beyond a mere reflex responsive to a stimulus from without; all doubt, therefore, concerning the actual existence of an instinct must be at an end, and the attempt to deduce it as a consequence of conscious deliberation be given up as hopeless. I will here adduce an instance as extraordinary as any we yet know of, showing, as it does, that many different purposes, which in the case of the higher animals require a complicated system of organs of motion, can be attained with incredibly simple means.

Arcella vulgaris is a minute morsel of protoplasm, which lives in a concave-convex, brown, finely reticulated sh.e.l.l, through a circular opening in the concave side of which it can project itself by throwing out pseudopodia. If we look through the microscope at a drop of water containing living arcellae, we may happen to see one of them lying on its back at the bottom of the drop, and making fruitless efforts for two or three minutes to lay hold of some fixed point by means of a pseudopodium. After this there will appear suddenly from two to five, but sometimes more, dark points in the protoplasm at a small distance from the circ.u.mference, and, as a rule, at regular distances from one another. These rapidly develop themselves into well-defined spherical air vesicles, and come presently to fill a considerable part of the hollow of the sh.e.l.l, thereby driving part of the protoplasm outside it. After from five to twenty minutes, the specific gravity of the arcella is so much lessened that it is lifted by the water with its pseudopodia, and brought up against the upper surface of the water-drop, on which it is able to travel. In from five to ten minutes the vesicles will now disappear, the last small point vanishing with a jerk. If, however, the creature has been accidentally turned over during its journey, and reaches the top of the water-drop with its back uppermost, the vesicles will continue growing only on one side, while they diminish on the other; by this means the sh.e.l.l is brought first into an oblique and then into a vertical position, until one of the pseudopodia obtains a footing and the whole turns over. From the moment the animal has obtained foothold, the bladders become immediately smaller, and after they have disappeared the experiment may be repeated at pleasure.

The positions of the protoplasm which the vesicles fashion change continually; only the grainless protoplasm of the pseudopodia develops no air. After long and fruitless efforts a manifest fatigue sets in; the animal gives up the attempt for a time, and resumes it after an interval of repose.

Engelmann, the discoverer of these phenomena, says (Pfluger's Archiv fur Physologie, Bd. II.): "The changes in volume in all the vesicles of the same animal are for the most part synchronous, effected in the same manner, and of like size. There are, however, not a few exceptions; it often happens that some of them increase or diminish in volume much faster than others; sometimes one may increase while another diminishes; all the changes, however, are throughout unquestionably intentional. The object of the air-vesicles is to bring the animal into such a position that it can take fast hold of something with its pseudopodia. When this has been obtained, the air disappears without our being able to discover any other reason for its disappearance than the fact that it is no longer needed... . If we bear these circ.u.mstances in mind, we can almost always tell whether an arcella will develop air-vesicles or no; and if it has already developed them, we can tell whether they will increase or diminish ... The arcellae, in fact, in this power of altering their specific gravity possess a mechanism for raising themselves to the top of the water, or lowering themselves to the bottom at will. They use this not only in the abnormal circ.u.mstances of their being under microscopical observation, but at all times, as may be known by our being always able to find some specimens with air-bladders at the top of the water in which they live."

If what has been already advanced has failed to convince the reader of the hopelessness of attempting to explain instinct as a mode of conscious deliberation, he must admit that the following considerations are conclusive. It is most certain that deliberation and conscious reflection can only take account of such data as are consciously perceived; if, then, it can be shown that data absolutely indispensable for the arrival at a just conclusion cannot by any possibility have been known consciously, the result can no longer be held as having had its source in conscious deliberation. It is admitted that the only way in which consciousness can arrive at a knowledge of exterior facts is by way of an impression made upon the senses. We must, therefore, prove that a knowledge of the facts indispensable for arrival at a just conclusion could not have been thus acquired. This may be done as follows: {111} for, Firstly, the facts in question lie in the future, and the present gives no ground for conjecturing the time and manner of their subsequent development.

Secondly, they are manifestly debarred from the category of perceptions perceived through the senses, inasmuch as no information can be derived concerning them except through experience of similar occurrences in time past, and such experience is plainly out of the question.

It would not affect the argument if, as I think likely, it were to turn out, with the advance of our physiological knowledge, that all the examples of the first case that I am about to adduce reduce themselves to examples of the second, as must be admitted to have already happened in respect of many that I have adduced hitherto. For it is hardly more difficult to conceive of a priori knowledge, disconnected from any impression made upon the senses, than of knowledge which, it is true, does at the present day manifest itself upon the occasion of certain general perceptions, but which can only be supposed to be connected with these by means of such a chain of inferences and judiciously applied knowledge as cannot be believed to exist when we have regard to the capacity and organisation of the animal we may be considering.

An example of the first case is supplied by the larva of the stag-beetle in its endeavour to make itself a convenient hole in which to become a chrysalis. The female larva digs a hole exactly her own size, but the male makes one as long again as himself, so as to allow for the growth of his horns, which will be about the same length as his body. A knowledge of this circ.u.mstance is indispensable if the result achieved is to be considered as due to reflection, yet the actual present of the larva affords it no ground for conjecturing beforehand the condition in which it will presently find itself.

As regards the second case, ferrets and buzzards fall forthwith upon blind worms or other non-poisonous snakes, and devour them then and there. But they exhibit the greatest caution in laying hold of adders, even though they have never before seen one, and will endeavour first to bruise their heads, so as to avoid being bitten. As there is nothing in any other respect alarming in the adder, a conscious knowledge of the danger of its bite is indispensable, if the conduct above described is to be referred to conscious deliberation. But this could only have been acquired through experience, and the possibility of such experience may be controlled in the case of animals that have been kept in captivity from their youth up, so that the knowledge displayed can be ascertained to be independent of experience. On the other hand, both the above ill.u.s.trations afford evidence of an unconscious perception of the facts, and prove the existence of a direct knowledge underivable from any sensual impression or from consciousness.

This has always been recognised, {113} and has been described under the words "presentiment" or "foreboding." These words, however, refer, on the one hand, only to an unknowable in the future, separated from us by s.p.a.ce, and not to one that is actually present; on the other hand, they denote only the faint, dull, indefinite echo returned by consciousness to an invariably distinct state of unconscious knowledge. Hence the word "presentiment," which carries with it an idea of faintness and indistinctness, while, however, it may be easily seen that sentiment dest.i.tute of all, even unconscious, ideas can have no influence upon the result, for knowledge can only follow upon an idea. A presentiment that sounds in consonance with our consciousness can indeed, under certain circ.u.mstances, become tolerably definite, so that in the case of man it can be expressed in thought and language; but experience teaches us that even among ourselves this is not so when instincts special to the human race come into play; we see rather that the echo of our unconscious knowledge which finds its way into our consciousness is so weak that it manifests itself only in the accompanying feelings or frame of mind, and represents but an infinitely small fraction of the sum of our sensations. It is obvious that such a faintly sympathetic consciousness cannot form a sufficient foundation for a superstructure of conscious deliberation; on the other hand, conscious deliberation would be unnecessary, inasmuch as the process of thinking must have been already gone through unconsciously, for every faint presentiment that obtrudes itself upon our consciousness is in fact only the consequence of a distinct unconscious knowledge, and the knowledge with which it is concerned is almost always an idea of the purpose of some instinctive action, or of one most intimately connected therewith. Thus, in the case of the stag-beetle, the purpose consists in the leaving s.p.a.ce for the growth of the horns; the means, in the digging the hole of a sufficient size; and the unconscious knowledge, in prescience concerning the future development of the horns.

Lastly, all instinctive actions give us an impression of absolute security and infallibility. With instinct the will is never hesitating or weak, as it is when inferences are being drawn consciously. We never find instinct making mistakes; we cannot, therefore, ascribe a result which is so invariably precise to such an obscure condition of mind as is implied when the word presentiment is used; on the contrary, this absolute certainty is so characteristic a feature of instinctive actions, that it const.i.tutes almost the only well-marked point of distinction between these and actions that are done upon reflection. But from this it must again follow that some principle lies at the root of instinct other than that which underlies reflective action, and this can only be looked for in a determination of the will through a process that lies in the unconscious, {115a} to which this character of unhesitating infallibility will attach itself in all our future investigations.

Many will be surprised at my ascribing to instinct an unconscious knowledge, arising out of no sensual impression, and yet invariably accurate. This, however, is not a consequence of my theory concerning instinct; it is the foundation on which that theory is based, and is forced upon us by facts. I must therefore adduce examples. And to give a name to the unconscious knowledge, which is not acquired through impression made upon the senses, but which will be found to be in our possession, though attained without the instrumentality of means, {115b} I prefer the word "clairvoyance" {115c} to "presentiment," which, for reasons already given, will not serve me. This word, therefore, will be here employed throughout, as above defined.

Let us now consider examples of the instincts of self-preservation, subsistence, migration, and the continuation of the species. Most animals know their natural enemies prior to experience of any hostile designs upon themselves. A flight of young pigeons, even though they have no old birds with them, will become shy, and will separate from one another on the approach of a bird of prey. Horses and cattle that come from countries where there are no lions become unquiet and display alarm as soon as they are aware that a lion is approaching them in the night. Horses going along a bridle-path that used to leave the town at the back of the old dens of the carnivora in the Berlin Zoological Gardens were often terrified by the propinquity of enemies who were entirely unknown to them. Sticklebacks will swim composedly among a number of voracious pike, knowing, as they do, that the pike will not touch them. For if a pike once by mistake swallows a stickleback, the stickleback will stick in its throat by reason of the spine it carries upon its back, and the pike must starve to death without being able to transmit his painful experience to his descendants. In some countries there are people who by choice eat dog's flesh; dogs are invariably savage in the presence of these persons, as recognising in them enemies at whose hands they may one day come to harm. This is the more wonderful inasmuch as dog's fat applied externally (as when rubbed upon boots) attracts dogs by its smell. Grant saw a young chimpanzee throw itself into convulsions of terror at the sight of a large snake; and even among ourselves a Gretchen can often detect a Mephistopheles. An insect of the genius bombyx will seize another of the genus parnopaea, and kill it wherever it finds it, without making any subsequent use of the body; but we know that the last-named insect lies in wait for the eggs of the first, and is therefore the natural enemy of its race. The phenomenon known to stockdrivers and shepherds as "das Biesen des Viehes" affords another example. For when a "da.s.sel" or "bies" fly draws near the herd, the cattle become unmanageable and run about among one another as though they were mad, knowing, as they do, that the larvae from the eggs which the fly will lay upon them will presently pierce their hides and occasion them painful sores. These "da.s.sel" flies - which have no sting - closely resemble another kind of gadfly which has a sting. Nevertheless, this last kind is little feared by cattle, while the first is so to an inordinate extent. The laying of the eggs upon the skin is at the time quite painless, and no ill consequences follow until long afterwards, so that we cannot suppose the cattle to draw a conscious inference concerning the connection that exists between the two. I have already spoken of the foresight shown by ferrets and buzzards in respect of adders; in like manner a young honey-buzzard, on being shown a wasp for the first time, immediately devoured it after having squeezed the sting from its body. No animal, whose instinct has not been vitiated by unnatural habits, will eat poisonous plants. Even when apes have contracted bad habits through their having been brought into contact with mankind, they can still be trusted to show us whether certain fruits found in their native forests are poisonous or no; for if poisonous fruits are offered them they will refuse them with loud cries. Every animal will choose for its sustenance exactly those animal or vegetable substances which agree best with its digestive organs, without having received any instruction on the matter, and without testing them beforehand. Even, indeed, though we a.s.sume that the power of distinguishing the different kinds of food is due to sight and not to smell, it remains none the less mysterious how the animal can know what it is that will agree with it. Thus the kid which Galen took prematurely from its mother smelt at all the different kinds of food that were set before it, but drank only the milk without touching anything else. The cherry-finch opens a cherry-stone by turning it so that her beak can hit the part where the two sides join, and does this as much with the first stone she cracks as with the last. Fitchets, martens, and weasels make small holes on the opposite sides of an egg which they are about to suck, so that the air may come in while they are sucking. Not only do animals know the food that will suit them best, but they find out the most suitable remedies when they are ill, and constantly form a correct diagnosis of their malady with a therapeutical knowledge which they cannot possibly have acquired. Dogs will often eat a great quant.i.ty of gra.s.s - particularly couch-gra.s.s - when they are unwell, especially after spring, if they have worms, which thus pa.s.s from them entangled in the gra.s.s, or if they want to get fragments of bone from out of their stomachs. As a purgative they make use of plants that sting. Hens and pigeons pick lime from walls and pavements if their food does not afford them lime enough to make their eggsh.e.l.ls with. Little children eat chalk when suffering from acidity of the stomach, and pieces of charcoal if they are troubled with flatulence. We may observe these same instincts for certain kinds of food or drugs even among grown-up people, under circ.u.mstances in which their unconscious nature has unusual power; as, for example, among women when they are pregnant, whose capricious appet.i.tes are probably due to some special condition of the ftus, which renders a certain state of the blood desirable. Field-mice bite off the germs of the corn which they collect together, in order to prevent its growing during the winter. Some days before the beginning of cold weather the squirrel is most a.s.siduous in augmenting its store, and then closes its dwelling. Birds of pa.s.sage betake themselves to warmer countries at times when there is still no scarcity of food for them here, and when the temperature is considerably warmer than it will be when they return to us. The same holds good of the time when animals begin to prepare their winter quarters, which beetles constantly do during the very hottest days of autumn. When swallows and storks find their way back to their native places over distances of hundreds of miles, and though the aspect of the country is reversed, we say that this is due to the acuteness of their perception of locality; but the same cannot be said of dogs, which, though they have been carried in a bag from one place to another that they do not know, and have been turned round and round twenty times over, have still been known to find their way home. Here we can say no more than that their instinct has conducted them - that the clairvoyance of the unconscious has allowed them to conjecture their way. {119a}

Before an early winter, birds of pa.s.sage collect themselves in preparation for their flight sooner than usual; but when the winter is going to be mild, they will either not migrate at all, or travel only a small distance southward. When a hard winter is coming, tortoises will make their burrows deeper. If wild geese, cranes, etc., soon return from the countries to which they had betaken themselves at the beginning of spring, it is a sign that a hot and dry summer is about to ensue in those countries, and that the drought will prevent their being able to rear their young. In years of flood, beavers construct their dwellings at a higher level than usual, and shortly before an inundation the field-mice in Kamtschatka come out of their holes in large bands. If the summer is going to be dry, spiders may be seen in May and April, hanging from the ends of threads several feet in length. If in winter spiders are seen running about much, fighting with one another and preparing new webs, there will be cold weather within the next nine days, or from that to twelve: when they again hide themselves there will be a thaw. I have no doubt that much of this power of prophesying the weather is due to a perception of certain atmospheric conditions which escape ourselves, but this perception can only have relation to a certain actual and now present condition of the weather; and what can the impression made by this have to do with their idea of the weather that will ensue? No one will ascribe to animals a power of prognosticating the weather months beforehand by means of inferences drawn logically from a series of observations, {119b} to the extent of being able to foretell floods. It is far more probable that the power of perceiving subtle differences of actual atmospheric condition is nothing more than the sensual perception which acts as motive - for a motive must a.s.suredly be always present - when an instinct comes into operation. It continues to hold good, therefore, that the power of foreseeing the weather is a case of unconscious clairvoyance, of which the stork which takes its departure for the south four weeks earlier than usual knows no more than does the stag when before a cold winter he grows himself a thicker pelt than is his wont. On the one hand, animals have present in their consciousness a perception of the actual state of the weather; on the other, their ensuing action is precisely such as it would be if the idea present with them was that of the weather that is about to come. This they cannot consciously have; the only natural intermediate link, therefore, between their conscious knowledge and their action is supplied by unconscious idea, which, however, is always accurately prescient, inasmuch as it contains something which is neither given directly to the animal through sensual perception, nor can be deduced inferentially through the understanding.

Most wonderful of all are the instincts connected with the continuation of the species. The males always find out the females of their own kind, but certainly not solely through their resemblance to themselves. With many animals, as, for example, parasitic crabs, the s.e.xes so little resemble one another that the male would be more likely to seek a mate from the females of a thousand other species than from his own. Certain b.u.t.terflies are polymorphic, and not only do the males and females of the same species differ, but the females present two distinct forms, one of which as a general rule mimics the outward appearance of a distant but highly valued species; yet the males will pair only with the females of their own kind, and not with the strangers, though these may be very likely much more like the males themselves. Among the insect species of the strepsiptera, the female is a shapeless worm which lives its whole life long in the hind body of a wasp; its head, which is of the shape of a lentil, protrudes between two of the belly rings of the wasp, the rest of the body being inside. The male, which only lives for a few hours, and resembles a moth, nevertheless recognises his mate in spite of these adverse circ.u.mstances, and fecundates her.

Before any experience of parturition, the knowledge that it is approaching drives all mammals into solitude, and bids them prepare a nest for their young in a hole or in some other place of shelter. The bird builds her nest as soon as she feels the eggs coming to maturity within her. Snails, land-crabs, tree-frogs, and toads, all of them ordinarily dwellers upon land, now betake themselves to the water; sea-tortoises go on sh.o.r.e, and many salt.w.a.ter fishes come up into the rivers in order to lay their eggs where they can alone find the requisites for their development. Insects lay their eggs in the most varied kinds of situations, - in sand, on leaves, under the hides and h.o.r.n.y substances of other animals; they often select the spot where the larva will be able most readily to find its future sustenance, as in autumn upon the trees that will open first in the coming spring, or in spring upon the blossoms that will first bear fruit in autumn, or in the insides of those caterpillars which will soonest as chrysalides provide the parasitic larva at once with food and with protection. Other insects select the sites from which they will first get forwarded to the destination best adapted for their development. Thus some horseflies lay their eggs upon the lips of horses or upon parts where they are accustomed to lick themselves. The eggs get conveyed hence into the entrails, the proper place for their development, - and are excreted upon their arrival at maturity. The flies that infest cattle know so well how to select the most vigorous and healthiest beasts, that cattle-dealers and tanners place entire dependence upon them, and prefer those beasts and hides that are most scarred by maggots. This selection of the best cattle by the help of these flies is no evidence in support of the conclusion that the flies possess the power of making experiments consciously and of reflecting thereupon, even though the men whose trade it is to do this recognise them as their masters. The solitary wasp makes a hole several inches deep in the sand, lays her egg, and packs along with it a number of green maggots that have no legs, and which, being on the point of becoming chrysalides, are well nourished and able to go a long time without food; she packs these maggots so closely together that they cannot move nor turn into chrysalides, and just enough of them to support the larva until it becomes a chrysalis. A kind of bug (cerceris bupresticida), which itself lives only upon pollen, lays her eggs in an underground cell, and with each one of them she deposits three beetles, which she has lain in wait for and captured when they were still weak through having only just left off being chrysalides. She kills these beetles, and appears to smear them with a fluid whereby she preserves them fresh and suitable for food. Many kinds of wasps open the cells in which their larvae are confined when these must have consumed the provision that was left with them. They supply them with more food, and again close the cell. Ants, again, hit always upon exactly the right moment for opening the coc.o.o.ns in which their larvae are confined and for setting them free, the larva being unable to do this for itself. Yet the life of only a few kinds of insects lasts longer than a single breeding season. What then can they know about the contents of their eggs and the fittest place for their development? What can they know about the kind of food the larva will want when it leaves the egg - a food so different from their own? What, again, can they know about the quant.i.ty of food that will be necessary? How much of all this at least can they know consciously? Yet their actions, the pains they take, and the importance they evidently attach to these matters, prove that they have a foreknowledge of the future: this knowledge therefore can only be an unconscious clairvoyance. For clairvoyance it must certainly be that inspires the will of an animal to open cells and coc.o.o.ns at the very moment that the larva is either ready for more food or fit for leaving the coc.o.o.n. The eggs of the cuckoo do not take only from two to three days to mature in her ovaries, as those of most birds do, but require from eleven to twelve; the cuckoo, therefore, cannot sit upon her own eggs, for her first egg would be spoiled before the last was laid. She therefore lays in other birds' nests - of course laying each egg in a different nest. But in order that the birds may not perceive her egg to be a stranger and turn it out of the nest, not only does she lay an egg much smaller than might be expected from a bird of her size (for she only finds her opportunity among small birds), but, as already said, she imitates the other eggs in the nest she has selected with surprising accuracy in respect both of colour and marking. As the cuckoo chooses the nest some days beforehand, it may be thought, if the nest is an open one, that the cuckoo looks upon the colour of the eggs within it while her own is in process of maturing inside her, and that it is thus her egg comes to a.s.sume the colour of the others; but this explanation will not hold good for nests that are made in the holes of trees, as that of sylvia phaenicurus, or which are oven-shaped with a narrow entrance, as with sylvia rufa. In these cases the cuckoo can neither slip in nor look in, and must therefore lay her egg outside the nest and push it inside with her beak; she can therefore have no means of perceiving through her senses what the eggs already in the nest are like. If, then, in spite of all this, her egg closely resembles the others, this can only have come about through an unconscious clairvoyance which directs the process that goes on within the ovary in respect of colour and marking.