skill. It is a vitally important matter in the psychology of animals, and involves the selective activity of intelligence. But we need not here repeat what has been already discussed on previous pages.

Let us pass, therefore, to another aspect of intelligent guidance, and in order to avoid referring back to instances before given in this chapter, let me further describe some observations on the young chicks, mention of which was made in a previous chapter. On the evening of their third day of active life, I placed before my little birds two objects new to their experience, a small worm and a yellow and black caterpillar-that of the cinnabar moth, so common in the summer on ragwort. The birds looked a little timidly and suspiciously at both of them. So far as I could judge, they were not more suspicious of one than of the other; they were probably suspicious of both, because the objects were rather larger than those which the chicks had been accustomed to peck at, and because they moved. They pecked at them timidly once or twice; but as it was getting late, and my chicks were rather sleepy, I felt it my duty, as their acting foster-mother, to put them to bed. Next morning, when they were fresh and vigorous, I repeated the experiment. Again both objects, the worm and the cinnabar caterpillar, were pecked at timidly, and eventually taken up in the bill and run off with. But the caterpillar, which is known to be distasteful to most birds, was dropped at once; while the worm was, after some comical efforts, bolted. Subsequently the caterpillar was occasionally pecked at, and more frequently merely looked at; but soon it was left unnoticed. Fresh small worms, on the other hand, were at once and with confidence snapped up and carried off, causing a most exciting chase, the fortunate possessor being allowed no peace for the delightful efforts necessary for swallowing the worm. I have, with other chicks, tried similar experiments with cinnabar caterpillars and loopers,

or other edible caterpillars of about the same size, and with similar results. And with ducklings the results are again similar. In no case, I may mention, was the caterpillar injured or the skin broken.

In these experiments and observations the points to be noticed are, first, the absence of any instinctive acquaintance with the difference between a nice worm and a nasty caterpillar; secondly, rapid profiting by experience after a few practical trials; thirdly, arising out of this, the discriminating by sight between the two objects; fourthly, the association of a nasty taste, or perhaps a disagreeable odour, with one of the objects, and pleasant gustatory results with the other; and, fifthly, guidance of subsequent action in accordance with the results of experience. In the last two points we have, in an elementary form, the basis of intelligent adaptation to circumstances. Intelligence, as I use the word in this work, is founded on experience; it involves the association of impressions and ideas, and it implies a power of control over the motor responses.

Let us now take a case illustrative of a rather more advanced stage of intelligence. I kept the chicks in my study, near a small gas-stove, so that I might regulate the temperature. For my first brood I made a sort of yard, paved with newspaper, and with newspaper walls propped against the fender, rugs, and so forth. (I now use wire netting.) At one side the turned-up newspaper rested against a chair. Blackie was a week old, and particularly bright and fresh, perhaps in consequence of his hearty meal of worsted. He was standing near the edge of the yard, pecking vigorously and persistently at something, which I discovered to be the number of the page of the newspaper. He then transferred his attention and his efforts to the somewhat turned-in corner of the newspaper, which was just within his reach. Seizing this, he pulled at it, bending the newspaper down, and thus making a breach in the wall of

my yard. Through this breach he stepped out into the wider world of my study. I put the paper back as before, caught the errant Blackie, and placed him in the yard, near the scene of his former efforts. He again pecked at the corner of the paper, again pulled it down, and again escaped. I then put him back as far as possible from this weak place in my poultry-yard. Presently, after some three or four minutes, he sauntered round to the corner, repeated his previous procedure, and again made his escape.

Unquestionably this is a more complex case of intelligence than the one I gave before. But it is of the same order. It was founded on experience; it involved the association of impressions and ideas; and it implied a power of profiting by the experience through the association. The chick found that a certain action, performed in the first instance, it would seem, without any view to any particular result, produced certain effects; those effects were pleasurable; an association was formed between the idea of pecking at that corner and the idea of walking out into the room. And, subsequently, the action of pulling down the newspaper was repeated for precisely the same reason that the action of picking up the worm was repeated-namely, because it had become associated through experience with pleasurable

consequences.

Enough has now been said to bring out the nature of that innate capacity for motor response due to organic inheritance, which forms the basis of all animal activities; and also the nature of those specialized forms of response, wherein consciousness is at most an epiphenomenon or associated adjunct, which are termed instinctive; and enough to show, by one or two simple examples, how intelligence guides the activities to individually adaptive results, through the association of ideas and the control of motor responses. We shall have to consider in future chapters other and more complex cases of intelligent guidance.

CHAPTER XIII.

THE PERCEPTION OF RELATIONS.

THE HE complexity of consciousness is so intricate, and yet so orderly, that it is difficult to trace all the varied threads of our mental tapestry. In previous chapters we have endeavoured, in our analysis, to pick out some of these threads. We have seen that in our visual impressions, sight being for us the dominant sense, retinal sensations coalesce or combine with motor sensations, and that seemingly simple impressions are therefore the products of a subtle synthesis. When we see a violet, the retinal sensations somewhat differently grouped in the two eyes, enter into synthetic union with certain motor sensations, the concomitants of movements of and within the eyeballs, whence arises an impression of a coloured and shaded object, possessed of a certain form, and located just there in the midst of a marginal field. But this impression forms the nucleus around which representative elements cluster. The visual field, how it is lighted and how the shadows fall, the relative size of the subsidiary objects, their grouping around the focal object,-all these involve representative elements which serve, so to speak, to give further body to the mental picture, and which result from a vast amount of visual experience, whereby retinal and motor elements have entered into a close co-ordination. The violet is a visual impression; but it is something more, it is a centre of aggregation. Its fragrant odour, for example, is suggested; and for me, as I have before mentioned, a particular spot in a quaint old garden, often visited in childhood, has a ten

dency to come to mind. That is to say, violets have a strong tendency, through association, to form the focal starting-point of a representative visual scene.

So far we have been dealing with the presentative elements of impressions, and with their representative revivals. Impressions as such are constituted solely by presentative elements synthetically combined, though they may rapidly accrete around themselves in further synthesis representative elements; and these representative elements, so far as we have already considered them, are merely the revivals of those sensations which constitute the presentative elements. And here it may be well to add a reminder that we defined a sensation as an undecomposable element in consciousness, due to an afferent impulse, or a combination of afferent impulses. Our analysis disclosed sensations of the special senses (retinal, auditory, olfactory, and so forth), sensations of pain and of general sensibility, motor sensations, and, it would seem, sensations of distance and solidity. These latter we found to be due to the combination of afferent impulses, which are probably physiological and infra-con

And it will be remembered that, in reply to the question, why the combination of certain infra-conscious impulses gives rise to a sensation having the quality of distance or of solidity, I said that I did not pretend to know. It is like the question why a combination of carbon and sulphur in certain proportions gives something so different from either constituent as the colourless liquid carbon disulphide. We can only say that, so far as we know, this is the way things are constituted. We here reach the limits of scientific analysis. In like manner of distance and solidity, we can only say that, under given conditions of stimulation, that is the form which impressions assume. Science cannot say why. Science has to be content with the fact that, so far as it is at present able to ascertain, this is the way in which such impressions are constituted.