with painful sensations. Other Octopi manifested still greater intelligence, for they pulled hermits out of their shells, taking care not to touch the zoophytes, realizing apparently that these were the stinging element. More remarkable than this is an observation made by Madame Jeannette Power. This lady on one occasion saw an Octopus, that held a stone by one of its arms, watching a large bivalve (Pinna) of which the shell was beginning to open. When this operation was complete the Octopus quickly inserted

the stone between the valves so as to prevent them from coming together again, and then proceeded to make a meal of the helpless bivalve.

Some of the Gastropods possess a well-marked "homing instinct", a particularly good example of this being afforded by the Common Limpet (Patella vulgata, fig. 1062). As elsewhere described (see vol. ii, p. 197) this creature lives on a particular spot, which in course of time becomes a more or less wellmarked "scar", to which it can hold so firmly as to defy waves and tide. From this home it wanders out to feed when uncovered by the water, and also when well covered. From such excursions, which may extend to a distance of several feet, it later on returns to settle down again on the scar, the surface

traversed being often very irregular and covered with acornbarnacles. When the animal gets back to the scar it of course arrives wrong way on, so to speak, and it quickly shuffles round so as to get into the proper position. A memory of locality certainly exists, and this would seem to imply intelligence. In the course of time a Limpet acquires a very accurate knowledge of the topography of a fair-sized area around its home, and if picked up when on the crawl and placed within this area is able to get home, though the time taken varies considerably. Exactly how it gets home we do not know. The simple cup-like eyes cannot render assistance, nor can we very well suppose that the otocysts help to guide it. Experiments appear to demonstrate that the animal does not smell its way back, and we are therefore reduced to touch, or to a "locality sense", or to both. The most obvious organs of touch are the two large tentacles on the head, with which the Limpet constantly touches the rock as it crawls, and it is no doubt by means of these that a good deal of the topographical knowledge is acquired. But as it can get home without the aid of these organs there must be some other organs of guidance. The edge of the mantle-flap is provided with a very large number of small tentacles which can be stretched out and actively moved, as they are sometimes, if not always, when the animal is adjusting itself on its scar. These perhaps have something to do with the matter, and so may still other sense-organs, but further investigation is required. The problem here to be solved, like most of those connected with locality-knowledge, is of a particularly baffling kind, though not to be regarded as insoluble. The Garden-Snail (Helix aspersa) is another Mollusc possessed of a "homing instinct "

INSTINCT AND INTELLIGENCE IN VERTEBRATES
(VERTEBRATA)

There is here an almost unlimited amount of material which might be discussed, but a few examples must suffice.

WARNING COLORATION.-A large number of animals possessed of noxious properties advertise their objectionable nature by means of bright though somewhat crude colours, and simple but striking patterns, the net result of which is to render them extremely conspicuous (see vol. ii, p. 301). Such are the

striped blazer" of the Wasp, and the spotted jacket of the Lady-Bird. Unless very hard pressed by hunger it appears that the foes of animals so coloured and marked give them a wide berth. But without careful observation and experiment it would remain an open question whether this resulted from Instinct or Intelligence, or a mixture of the two. The cases which have so far been properly investigated appear to prove that Intelligence here comes into play, and that a young animal has to learn from experience that some things are good to eat and others not. The thorough and long-continued researches of Lloyd Morgan upon artificially - hatched chicks definitely prove that they at least have to acquire such useful knowledge for themselves. He thus describes (in Animal Behaviour) how some of his chicks learnt that alternate bands of black and orange, as possessed by the caterpillars of the Cinnabar Moth, are associated with disagreeable sensations:-"The following experiment was made with young chicks. Stripes of orange and black paper were pasted beneath glass slips, and on them meal moistened with quinine was placed. On other plain slips meal moistened with water was provided. The young birds soon learnt to avoid the bitter meal, and then would not touch plain meal if it was offered on the banded slip. And these birds, save in two instances, refused to touch cinnabar caterpillars, which were new to their experience. They did not, like other birds, have to learn by particular trials that these caterpillars are unpleasant. Their experience had already been gained through the banded glass slips; or so it seemed. I have also found that young birds who had learnt to avoid cinnabar caterpillars left wasps untouched."

NEST-BUILDING IN BIRDS.-There can be no reasonable doubt that in its main features the nest-building of birds is a matter of instinct. One of the best proofs of this is afforded by cases where individuals kept in captivity from the time of hatching, under conditions which excluded the possibility of instruction or imitation, have nevertheless constructed nests of the kind proper to their species. Further experiments, however, are much to be desired, especially on birds which indulge in architecture of such characteristic kind as to be quite unmistakable. It would, of course, be necessary to make the nesting conditions in such cases as natural as possible. Other instincts, tending to the benefit

of the eggs or young, are often associated with that for nestbuilding. Of this the Eider-Duck (Somateria mollissima, fig. 1063) may be taken as an example. Egg-laying and building

are here not consecutive acts, but the former takes place at intervals during the latter, in a somewhat variable fashion. Three successive stages are shown in the illustration, which is taken from photographs by Mr. R. A. L. Van Someren. The first represents four eggs resting in the incomplete nest, and the second (on a larger scale) the complete downlined nest with its full complement of eggs. The third figure shows the same nest during the temporary absence of the mother-bird, and illustrates an interesting associated instinct. Before leaving her duties she had pulled the down over the eggs, so as to cover them completely, an act distinctly conducive to their welfare. For, snugly tucked up under their "eider-down quilt", they were not only kept warm, but also, as the figure clearly proves, effectively screened from observation.

But although nest-building is almost certainly instinctive in the main, it is subject to modification in individual cases in ways which vouch for the intelligence of the builders. And such modification may affect the style, materials, and place of construction. Oftenquoted illustrations are those of the House-Swallow and HouseMartin, which have taken advantage of the evolution of human civilization so far as concerned with domestic architecture.

This change of habit, of course, took place in the remote past, but the following very interesting modern example of precisely similar kind is given by Headley (in The Structure and Life of Birds):-"The Palm Swift in Jamaica till 1854 always built in palms. But in Spanish Town, when two cocoa-nut palms were blown down, they drove out the Swallows from the Piazza of the House of Assembly and built between the angles formed by the beams and joists." Of other such cases Newton thus writes (in A Dictionary of Birds):-" But though in a general way the dictates of hereditary instinct are rigidly observed by Birds, in many species a remarkable degree of elasticity is exhibited or the rule of habit is rudely broken. Thus, the noble Falcon, whose ordinary eyry is on the beetling cliff, will for the convenience of procuring prey condescend to lay its eggs on the ground in a marsh, or appropriate the nest of some other bird in a tree. The Golden Eagle, too, remarkably adapts itself to circumstances, now rearing its young on a precipitous ledge, now on the arm of an ancient monarch of the forest, and again on a treeless plain, making a humble home amid grass and herbage. Herons also show the same versatility, and will breed according to circumstances in an open fen, on sea-banks, or (as is most usual) on lofty trees. Such changes are easy to understand. The instinct of finding food for the family is predominant, and where most food is, there will the feeders be gathered together. This explains, in all likelihood, the associated bands of Ospreys or Fish-Hawks, which in North America breed (or used to breed) in large companies where sustenance is plentiful, though in the Old World the same species brooks not the society of aught but its mate.'

MIGRATION OF BIRDS.-Nothing can be more familiar than the fact that innumerable species of birds undertake periodic journeys, often of extreme length, from one region to another, and at the same time nothing in the entire realm of natural history is more mysterious. Broadly speaking, the same migrant species has its own line of travel between its two places of residence. The Golden Plovers, for example, of the northern part of North America, fly south to the north of South America. via the Bermudas and Antilles. The paths of a number of species are more or less coincident, in many cases, to form what is known as a "migration route", and some of these routes