performs the feat, “because it feels as if it must,” and is quite ignorant of the purpose to be subserved.

It is no doubt quite beyond our power to ascertain accurately the mental condition of a spider, but it is perfectly easy to make a few illuminating experiments on two points which have a very decided bearing on intelligence:—the development of the senses, and the degree of what has been called educability, or the power of learning from experience. To what extent can the spider see, hear, smell, feel, taste? How far is it capable of varying its action as the result of experience? The senses, as far as we know, are the principal—if not the only—avenues by which external impressions can reach the seat of intelligence, and there is no surer indication of the intelligence of an animal than the degree to which it is susceptible of education. Probably most readers know the immortal story of the pike cited by Darwin in the Descent of Man. The pike was in an aquarium, separated by a sheet of glass from a tank in which were numerous small fish. Not till three months had expired did the pike cease to dash itself against the glass partition in its attempts to seize the fish in the neighbouring tank. It then desisted and had evidently learnt something—but what? After three months, the glass partition was removed, but the pike refused to attack those particular fish, though it immediately seized any new specimens introduced to the tank. All that it had apparently learnt was that an attack on a particular fish resulted in a violent blow on the nose. Some degree of intelligence must be conceded to the pike, but it can hardly be considered of a high order.

Now the garden-spider possesses eight eyes, and might be expected to see fairly well, but the experimenter will very soon come to the conclusion that the habitual use it makes of them—at all events in day-light—is very slight. Touch a web with a vibrating tuning-fork and the spider will rush to the spot and investigate the instrument with its fore-legs before distinguishing it from a fly. Remember, however, that this is only true of what are sometimes called sedentary spiders; species which hunt their prey have much better vision. Yet even among sedentary spiders the power of sight is not negligible, for a most trustworthy observer states that he has several times seen Meta segmentata, a very common small Epeirid, drop from its web to secure an insect on the ground beneath, and return with it by way of the drop line, and the same action has been observed in the case of Theridion, which spins an irregular snare.

There are peculiar difficulties attending experiments on the subject of hearing. An absolutely deaf person may be aware of the sounding of a deep organ note through the sense of feeling, and a well-known experimenter was on the point of drawing interesting conclusions from the behaviour of a spider in response to the notes of a flute, when he found that precisely the same results were obtained by a soundless puff of air. It seems hardly possible to make sure, in the case of a spider in a snare, that the sound vibrations are not felt, apart from any sense of hearing, and it is a remarkable fact that it is only the snare-spinning spiders that make any response to sounds:—free-roving spiders are apparently quite deaf.

In experimenting with sound we must take two precautions: the instrument used must not necessitate any marked action which may be visible to the spider, nor must it give rise to palpable air-currents. These requirements are best met by a tuning-fork of not too low a pitch. We cannot feel the air vibrations emanating from it, but can only perceive them by the ear, but we have no proof that the spider’s sense of touch ceases precisely at the same point as our own. However, no better instrument for experiment seems to be available, so we take a tuning-fork, and approach it cautiously—in the quiescent state—towards the spider, stationed, we will suppose, in the centre of its snare. No notice is taken, and we carefully withdraw it, set it vibrating, and approach it again in the same manner. There is now generally a response, the spider raising its front legs and extending them in the direction of the fork, or, if the sound is loud, dropping suddenly by a thread and remaining suspended some inches below the snare. The experiment should be repeated several times with the fork sometimes still, sometimes vibrating, and the conclusion arrived at will be that the spider is aware of the vibrating fork—but by which sense? It is noteworthy that a fork giving a low note is always most effective.

Now here is a very remarkable fact. In two widely different groups of spiders—the Theraphosidae or so called “bird-eating spiders” and the Theridiidae—there are species with a stridulating or sound-making apparatus, and we should hardly expect a deaf creature to evolve an elaborate mechanism for the production of sound. This is a matter, however, that we shall discuss later.

No amount of research has succeeded in localising the sense of hearing in spiders, supposing it to exist. The creature may lose any of its five pairs of limbs (four pairs of legs and one pair of pedipalps) without alteration in its response to sound. If the front legs are missing the second pair are raised when the vibrating fork is approached.

It is fairly easy to test the sense of smell in these creatures, the only necessary precaution being that no acid or pungent substances capable of having an irritating effect on the skin, such as vinegar or ammonia, must be employed. Such perfumes as lavender or heliotrope are free from this defect. Take a clean glass rod and present it to the spider as before, and no notice is taken. Now dip it in oil of lavender, allow it to dry, and present it again. Most spiders respond to such a test, Epeirids generally raising the abdomen, and rubbing one or other of the legs against the jaws, while jumping spiders generally raise the head and back away from the rod. Different essences produce different effects, but there is seldom any doubt that the creature is aware of their presence; it is not deficient in the sense of smell, but its localisation has hitherto baffled research.

The sense of taste does not seem to have been made the subject of any definite experiments among spiders, though such experiments might well lead to interesting conclusions, and the reader might do worse than undertake some on his own account. It would be easy, for instance, to supply a garden-spider with various insects which are generally rejected by other insectivorous animals, and to note its behaviour. It might refuse to have anything to do with them, or it might sample them and turn away in disgust. In the first case the explanation might be that it was warned of their probably evil taste by their coloration or smell, but in any case here is an interesting little field for research. It is the general belief among arachnologists that the sense of taste is well developed among spiders, and it is highly improbable that a sense so necessary for the discrimination of suitable food should be lacking in animals with so respectable a sensory equipment.

There is no doubt at all that the sense of touch is extremely well developed in spiders, especially perhaps, in the sedentary groups, and it is probable that, under ordinary circumstances, the garden-spider works almost entirely by its guidance. Whether in the centre of the web or in its retreat under a neighbouring leaf it is in direct communication with every part of its snare by silken lines, and the least disturbance usually suffices to bring it to the spot; and then, as we have