 6 Evolution, as we have seen in a previous chapter of the series, is another word for race history. It means the ceaseless process of becoming, linking generation to generation of living creatures. The doctrine of evolution states the fact that the present is the child of the past and the parent of the future. It comes to this, that the living plants and animals we know are descended from ancestors on the whole simpler, and these from others likewise simpler, and so on, back and back, till we reach the first living creatures, of which unfortunately we know nothing. Evolution is a process of racial change in a definite direction whereby new forms arise, take root and flourish, alongside of or in place of their ancestors, which were in most cases rather simpler in structure and behavior. The rock record, which cannot be wrong, though we may read it wrongly, shows clearly that there was once a time in the history of the earth when the only back-boned animals were fishes. Ages passed and there evolved amphibians with fingers and toes scrambling on to dry land. Ages passed and there evolved reptiles in bewildering perfusion. There were fish lizards and sea serpents, terrestrial dragons and flying dragons, a prolific and varied stock. From the terrestrial dinosaurs it seems that birds and mammals arose. In succeeding ages there evolved all the variety of birds and all the variety of mammals. Until at last arose the man. The question is whether similar processes of evolution are still going on. We are so keenly aware of rapid changes in mankind, though these concern the social heritage much more than the flesh and blood natural inheritance, that we find no difficulty in the idea that evolution is going on in mankind. We know the contrast between modern man and primitive man, and we are convinced that in the past, at least, progress has been reality. That degeneration may set in is an awful possibility, involution rather than evolution, but even if going back became for a time the rule, we cannot give up the hope that the race would recover itself and begin afresh to go forward. For although there have been long retrogressions in the history of life, continued through unthinkably long ages, and although great races, the flying dragons, for instance, have become utterly extinct, leaving no successors whatsoever, we feel sure that there has been on the whole a progress towards a nobler, more masterful, more emancipated, more intelligent, and better forms of life. A progress towards what mankind at its best is always regarded as best, that is, affording most enduring satisfaction. So we think of evolution going on in mankind, evolution checkered by involution, but on the whole progressive evolution, evolutionary prospect for man. It is not likely that man's body will admit of great change, but there is room for some improvement, for instance, in the superfluous length of the food canal and the overcrowding of the teeth. It is likely, however, that there will be constitutional changes, for instance, of prolonged youthfulness, a higher standard of healthfulness, and a greater resistance to disease. It is justifiable to look forward to great improvements in intelligence and in control. The potentialities of the human brain, as it is, are far from being utilized to the full, and new departures of promise or of continual occurrence. What is of great importance is that the new departures are variations which emerge in fine children should be fostered, not nipped in the bud, by the social environment, education included. The evolutionary prospect for man is promising, but it is very important to realize that among plant and animals, likewise, evolution is going on. The fountain of change, variability. On an ordinary big clock we do not readily see that even the minute hand is moving. And if the clock struck only once in a hundred years we can conceive of people arguing whether the hands did really move at all. So it often is with the changes that go on from generation to generation in living creatures. The flux is so slow, like the flowing of a glacier, that some people fail to be convinced of its reality. And it must, of course, be admitted that some kinds of living creatures, like the lamp-shell ligula or the pearly nautilus, hardly change from age to age, whereas others, like some of the birds and butterflies, are always giving rise to something new. The evening primrose among plants and the fruit fly, Drosophila, among animals, are well-known examples of organisms which are a present in a sporting or mutating mood. Certain dark varieties of moth, for instance, of the peppered moth, are taking the place of the paler type in some parts of England, and the same is true of some dark forms of sugar bird in the West Indian Islands. Very important is the piece of statistics worked out by Professor R. C. Punnett that if a population contains .001% of a new variety, and if that variety has even a 5% selection advantage over the original form, the latter will almost completely disappear in less than a hundred generations. This sort of thing has been going on all over the world for untold ages, and the face of animate nature has consequently changed. We are impressed by striking novelties that crop up, a clever dwarf, a musical genius, a calculating boy, a cock with a ten-foot tail, a wonder-horse with a mane reaching to the ground, a tailless cat, a white blackbird, a copper beach, a greater selendine with much cut-up leaves, but this sort of mutation is common, and smaller, less brusque variations are commoner still. They form the raw materials of possible evolution. We are actually standing before an apparently inexhaustible fountain of change. This is evolution going on. The Sporting Jellyfish It is of interest to consider a common animal like the Jellyfish Aurelia. It is admirably suited for a leisurely life in the open sea, where it swims about by contracting its saucer-shaped body, thus driving water out from its concavity. By means of millions of stinging cells on its four frilled lips and on its marginal tentacles it is able to paralyze and lasso minute crustaceans and the like, which it then wafs into its mouth. It has a very eventful life history, for it has in its early youth to pass through a fixed stage, fastened to rock or seaweed, but it is a successful animal well suited for its habitat, and practically cosmopolitan in its distribution. It is certainly an old established creature, yet it is very variable in color and size, and even in internal structure. Very often it is the size of a saucer or a soup plate, but giants over two feet in diameter are well known. Much more important, however, than variation in color and size are the inborn changes in structure. Normally a Jellyfish has its parts in four or multiples of four. Thus it is four frilled lips, four tufts of digestive filaments in its stomach, and four brightly colored reproductive organs. It is eight sense organs round the margin of its disc, eight branched and eight unbranched radio canals running from the central stomach to a canal round the circumference. The point of giving these details is just this, that every now and then we find a Jellyfish with its parts in sixes, fives, or threes, and with a multitude of minor idiosyncrasies. Even in the well established Jellyfish there is a fountain of change. Evolution of Plants It is instructive to look at the various kinds of cabbages such as cauliflower and brussel sprouts, kale and curly greens, and remember that they are all sky ends of the not very promising wild cabbage found on our shores, and are not all the aristocrat apple trees of our orchards, descended from the pubian crab-apple of the roadside? We know far too little about the precise origin of our cultivated plants, but there is no doubt that after man got a hold of them he took advantage of their variability to establish race after race, say, of rose and chrysanthemum, of potato and cereal. The evolution of cultivated plants is continuing before our eyes, and the creations of Mr. Luther Burbank, such as the stoneless plum and the primus berry, the spineless cactus and the Shasta Daisy, are merely striking instances of what is always going on. There is reason to believe that the domestic dog has risen three times from three distinct ancestors, a wolf, a jackal, and a coyote. So a multiple pedigree must be allowed for in the case of the dog, and the same is true in regard to some other domesticated animals. But the big fact is the great variety of breeds that man has been able to fix after he once got started with a domesticated type. There are over two hundred well-marked breeds of domestic pigeons, and there is very strong evidence that all are descended from the wild rock dove. Just as the numerous kinds of poultry are descended from the jungle fowl of some parts of India and the Mele Islands. Even more familiar is the way in which man has, so to speak, unpacked the complex fur of the wild rabbit, and established all the numerous color varieties which we see among domestic rabbits. And apart from color varieties there are long-haired Angoras and quaint lop-eared forms, and many more besides. All this points to evolution going on. The Romance of the Wheat It is well known that Neolithic man grew wheat, and some authorities have put the date of the first wheat harvest at between fifteen thousand and ten thousand years ago. The ancient civilizations of Babylonia, Egypt, Crete, Greece, and Rome were largely based on wheat, and it is highly probable that the first great wheat fields were in the fertile land between the Tigris and the Euphrates. The oldest Egyptian tombs that contain wheat, which by the way never germinates after its millennia of rest, belong to the First Dynasty, and are about six thousand years old. But there must have been a long history of wheat before that. Now it is a very interesting fact that the almost certain ancestor of the cultivated wheat is at present living on the arid and rocky slopes of Mount Hermon. It is called Triticum Hermonus, and it is varying notably today, as it did long ago when it gave rise to the emmer, which was cultivated in the Neolithic age, and is the ancestor of all our ordinary wheats. We must think of Neolithic man noticing the big seeds of this Hermon grass, gathering some of the heads, breaking the brittle spikelet-bearing axis in his fingers, knocking off the rough awns or bruising the spikelets in his hand, till the glooms or chaff separated off and could be blown away, chewing a mouth full of the seeds, and resolving to sow and sow again. That was the beginning of a long story, in the course of which man took advantage of the numerous variations that cropped up in this sporting stock, and established one successful race after another on his fields. Virgil refers, in the Georgics, to the gathering of the largest and fullest ears of wheat in order to get good seed for another sowing, but it was not till the first quarter of the 19th century that the great step was taken by men like Patrick Sheriff of Heddington of deliberately selecting individual ears of great excellence and segregating their progeny from mingling with mediocre stock. This is the method which has been followed with remarkable success in modern times. One of the factors that assisted the Allies in overcoming the food crisis in the very darkest period of the war was the virtue of marquee wheat, a very prolific, early ripening, hard red spring wheat with excellent milling and baking qualities. It is now the dominant spring wheat in Canada and the United States, and it has enormously increased the real wealth of the world in the last ten years, as of 1921. Now our point is simply that this marquee wheat is a fine example of evolution going on. In 1917 upwards of 250 million bushels of this wheat were raised in North America, and in 1918 upwards of 300 million bushels. Yet the whole originated from a single grain planted in an experimental plot at Ottawa by Dr. Charles E. Saunders so recently as the spring of 1903. We must not dwell too long on this particular instance of evolution, though it has met much to our race. We wish, however, following Professor Buller's essays on wheats, 1919, to explain the method by which this good seed was discovered. From one we may learn all. The parent of marquee wheat on the male side was the mid-Europe red-fife, a first-class cereal. The parent on the female side was less promising, a rather nondescript, not pure bread wheat called red calcutta, which was imported from India into Canada about thirty years ago. The father was part of a cargo that came from the Baltic to Glasgow, and was happily included in a sample sent on to David Fife in Ontario about 1842. From one kernel of the sample David Fife started his stock of red-fife, which was crossed by Dr. Saunders with hard-red calcutta. The result of the cross was a medley of types, nearly a hundred varieties altogether, and it was in scrutinizing these that Dr. Saunders hit upon marquee. He worked steadily through the material, studying head after head of what resulted from sowing, and selecting out those that gave most promise. Each of the heads selected was propagated, most of the results were rejected, the elect were sifted again and yet again, and finally marquee wheat emerged, rich in constructive possibilities, probably the most valuable food plant in the world. It is like a romance to read that the first crop of the wheat that was destined within a dozen years to overtax the mightiest elevators in the land was stored away in the winter of 1904 to 1905 in a paper packet no larger than an envelope. Thus from the wild wheat of Mount Hermond there evolved one of the most important food plants of the world. This surely is evolution going on. Nothing gives us a more convincing impression of evolution in being than a succession of pictures of the animal life of a country in different ages. Dr. James Ritchie, a naturalist of distinction, has written a masterly book, The Influence of Man on Animal Life in Scotland, published 1920, in which we get the succession of pictures. Within itself, he says, a fauna is in a constant state of uneasy restlessness, an assemblage of creatures which in its parts ebbs and flows as one local influence or another plays upon it. There are temporary and local changes, endless disturbances and readjustments of the balance of nature. One year there is a plague of field voles, perhaps next year grouse disease is rife. In one place there is a huge increase of starlings, in another place of rabbits. Here cock-chafers are in the ascent and there the moles are spoiling the pasture. But while the parts fluctuate the fauna as a whole follows a path of its own. As well as internal tides which swing to and fro about an average level, there is a drift which carries the fauna bodily along an irretraceable course. This is partly due to considerable changes of climate, or climate calls the tune to which living creatures dance. But it is also due to new departures among the animals themselves. We need not go back to the extinct animals and lost faunas of past ages, for Britain has plenty of relics of these, which illustrate the reality of the faunal drift. But it may be very useful, in illustration of evolution and being, to notice what has happened in Scotland since the end of the Great Ice Age. Some nine thousand years ago or more certain long-headed square-jawed short-limbed but agile hunters and fishermen, whom we call Neolithic man, established themselves in Scotland. What was the state of the country then? It was a country of swamps, low forests of birch, alder and willow, fertile meadows, and snow-capped mountains. Its estuaries penetrated further inland than they now do, and the sea stood at the level of the fifty-foot beach. On its plains and in its forests roam many creatures which are strange to the fauna of today. The elk and the reindeer, wild cattle, the wild boar and perhaps wild horses, a fauna of large animals which paid toll to the European lynx, the brown bear and the wolf. In all likelihood the marshes resounded to the boom of the bittern and the plains to the breeding-calls of the crane and the Great Bustard. Now what happened to this kingdom of Caledonia which Neolithic man had found? He began to introduce domesticated animals, and that meant a thinning of the ranks of predacious creatures. Safety first was the dangerous motto in obedience to which man exterminated the lynx, the brown bear and the wolf. Other creatures, such as the great awk, were destroyed for food, and others like the martin for their furs. Small pests were destroyed to protect the beginnings of agriculture. Larger animals like the boar were hunted out of existence. Others like the pearl-bearing river mussels yielded to subtler demands. No doubt there was protection also, protection for sport, for utility, for aesthetic reasons, and because of humane sentiments even wholesome superstitions have safeguarded the robin red breast and the wren. There were introductions to the rabbit for utility, the pheasant for sport, and the peacock for amenity, and every introduction, every protection, every killing out had its far-reaching influences. But if we are to picture the evolution going on we must think also of man's indirect interference with animal life. He destroyed the forests. He cultivated the wild. He made bridges. He allowed aliens like rats and cockroaches to get in unawares. Of course he often did good as when he drained swamps and got rid of the mosquitoes which once made malaria rife in Scotland. What has been their net result? Not, as one might think for a moment, a reduction in the number of different kinds of animals. Fourteen or so species of birds and beasts have been banished from Scotland since man interfered, but as far as numbers go they have been more than replaced by deliberate introductions like fallow deer, rabbit, squirrel, and pheasant, and by accidental introductions like rats and cockroaches. But the change is rather in quality than in quantity. The smaller have taken the place of the larger, rather impaltry pygmies of noble giants. Thus we get a vivid idea that evolution, especially when man interferes, is not necessarily progressive. That depends on the nature of the sieves with which the living materials are sifted. As Dr. Ritchie Well says, the standard of the wild fauna as regards size has fallen and is falling, and it is not in size only that there is loss. There is a deterioration of quality. For how can the increase of rabbits and sparrows and earthworms and caterpillars and the addition of millions of rats and cockroaches and crickets and bugs ever take the place of those fine creatures round the memories of which the glamour of Scotland's past still plays? The reindeer and the elk, the wolf, the brown bear, the lynx and the beaver, the bustard, the crane, the bumbling bittern, and many another, lost or disappearing. Thus we see again that evolution is going on. THE ADVENTURERS All through the millions of years during which animals have tenanted the earth and the waters under the earth, there has been a search for new kingdoms to conquer, for new corners in which to make a home. And this still goes on. It has been in is one of the methods of evolution to fill every niche of opportunity. There is a spider that lives inside a pitcher plant, catching some of the inquisitive insects which slip down the treacherous internal surface of the trap. There is another that makes its home in crevices among the rocks on the shore of the Mediterranean, and even in empty tubular shells keeping the water out more or less successfully by spinning threads of silk across the entrance to its retreat. The beautiful brine-trip, Artemia Salina, that used to occur in British salterns, has found a home in the dense waters of the Great Salt Lake of Utah. Several kinds of earthworms have been found uptrees, and there is a fish, arches, that climbs on the stones of steep mountain torrents of the Andes. The intrepid explorers of the Scotia voyage found quite a number of arctic turns spending our winter within the summer of the Antarctic Circle, which means girdling the globe from pole to pole, and every now and then there are incursions of rare birds, like palaces, sand-grouse, into Britain, just as if they were prospecting in search of a promised land. Twice or thrice the distinctively North American kill-deer plover has been found in Britain. Having somehow or other got across the Atlantic, we miss part of the meaning of evolution if we do not catch this note of insurgence and adventure, which some animal or other never ceases to sound, though many established themselves in a security not easily disturbed, and though a small minority give up the struggle against the stream and are content to acquiesce as parasites or rottenness eaters in a drifting life of ease. More important than very peculiar cases is the broad fact that over and over again in different groups of animals there have been attempts to master different kinds of hots, such as the underground world, the trees, the fresh waters and the air. There are burrowing amphibians, burrowing reptiles, burrowing birds, and burrowing mammals. There are tree toads, tree snakes, tree lizards, tree kangaroos, tree sloths, tree shrews, tree mice, tree porcupines, and so on. Enough of a list to show, without mentioning birds, how many different kinds of animals have entered upon an arboreal apprenticeship, an apprenticeship often with far-reaching consequences. What the freeing of the hen, from being an organ of terrestrial support has meant in the evolution of monkeys, is a question that gives a spur to our imagination. The Case of the Robber Crab On some of the coral islands of the Indian and Pacific Oceans there lives a land crab, Burgess, which has learned to breathe on land. It breathes dry air by means of curious blood-containing tufts in the upper part of its gill cavity, and it has also rudimentary gills. It is often about a foot long, and it has very heavy great claws, especially on the left hand side. With this great claw it hammers on the eye-hole of a coconut, from which it is torn off the fibrous husk. It hammers until a hole is made by which it can get at the pulp. Part of the shell is sometimes used as a protection for the soft abdomen. For the robber crab, as it is called, is an offshoot from the hermit crab stock. Every year this quaint explorer, which may go far up the hills and climb the cocoa palms, has to go back to the sea to spawn. The young ones are hatched in the same state as in our common shore-crab. That is to say they are free-swimming larvae, which pass through an open water period before they settle down on the shore, and eventually creep up on to dry land. Just as open water turtles lay their eggs on sandy shores, going back to their old terrestrial haunt, so the robber crab, which has almost conquered the dry land, has to return to the seashore to breed. There is a peculiar interest in the association of the robber crab with the cocoa palm, for that tree is not a native of these coral ions, but has been introduced, perhaps from Mexico, by the Polynesian mariners before the discovery of America by Columbus. So the learning to deal with coconuts is a recent achievement, and we are face to face with a very good example of evolution going on. The story of the salmon. In late autumn or in winter the salmon spawn in the rivers. The female makes a shallow trough in the gravel by moving her tail from side to side, and therein lays many eggs. The male, who is in attendance, fertilizes these with the milk, and then the female covers them deeply with gravel. The process is repeated over and over again for a week or more till all the eggs are shed. For three or four months the eggs develop, and eventually there emerge the larvae or alavins which lurk among the pebbles. They cannot swim much, for they are encumbered by a big legacy of yolk. In a few weeks, perhaps eight, the protruding bag of yolk has disappeared, and the fry, about an inch long, begin to move about more actively, and defend for themselves. By the end of the year they have grown to be rather trout like par, about four inches long. In two years these are double that length. Usually in the second year, but it may be earlier or later, the par becomes silvery smolts, which go out to sea, usually about the month of May. They feed on young herring and the like, and grow large and strong. When they are about three and a half years old they come up the rivers as grilse and may spawn, or they may pass through the whole grilse stage in the sea and come up the rivers with all the characters of the full-grown fish. In many cases the salmon spawn only once, and some, they are called kelts after spawning, are so much exhausted by starting a new generation that they die or fall a victim to otters and other enemies. In the case of the salmon of the North Pacific, in the genus Uncorroincus, not Salmo, all the individuals die after spawning, none being able to return to the sea. It must be remembered that full-grown salmon do not as a rule feed in fresh water, though they may be unable to resist snapping at the anglers' strange creations. A very interesting fact is that the salmon keeps as it were a diary of its movements, which vary a good deal in different rivers. This diary is written in the scales, and a careful reading of the concentric lines on the scales shows the age of the fish, and when it went out to sea, and whether it is spawned or not, and more besides. INTERPRETATION OF THE SAMON'S STORY When an animal frequents two different haunts, in one of which it breeds, it is very often safe to say that the breeding place represents the original home. The flounder is quite comfortable far up the rivers, but it has to go to the shore waters to spawn, and there is no doubt that the flounder is a marine fish which has recently learned to colonize the fresh waters. Its relatives, like place and soul, are strictly marine. But it is impossible to make a dogma of the rule that the breeding place corresponds to the original home. Thus some kinds of bass, which belong to the marine family of sea perches, live in the sea, or in estuaries, while two have become permanent residents in fresh water. Or, again, the members of the herring family are very distinctively marine, but the shad which belong to this family spawn in rivers and may spend their lives there. So there are two different ways of interpreting the life history of the salmon. Some authorities regard the salmon as a marine fish which is establishing itself in fresh water, but others read the story the other way and regard the salmon as a member of a freshwater race that is taken to the sea for feeding purposes. In regard to trout, we know that the ranks of those in rivers and lakes are continually being reinforced by migrants from the sea, and that some trout go down to the sea while others remain in the fresh water. We know also in regard to a related fish, the char, that while the great majority of kinds are now permanent residents in cold and deep, isolated northern lakes, there are arctic forms which live in the sea but enter the rivers to spawn. These facts favor the view that the salmon was originally a marine fish, but there are arguments on both sides, and for our present purpose the important fact is that the salmon is conquering two haunts, its evolution is going on. The Romance of the Eel Early in summer, at dates varying with the distance of the rivers from the open Atlantic, crowds of young eels or elvers come upstream. Sometimes the procession of eel-fare includes thousands of individuals, each about the length of our first finger, and as thick as a stout knitting needle. They obey an inborn impulse to swim against the stream, seeking automatically to have both sides of their body equally stimulated by the current. So they go straight ahead. The obligation works only during the day, for when the sun goes down behind the hills, the elvers snuggle under stones or beneath the bank and rest till dawn. In the course of time they reach the quiet upper reaches of the river, or go up rivulets and drain-pipes to the isolated ponds. Their impulse to go on must be very imperious, for they may wriggle up the wet moss by the side of a waterfall, or even make a short excursion in a damp meadow. In the quiet flowing stretches of the river, or in the ponds, they feed and grow for years and years. They account for a good many young fishes. Eventually, after five or six years in the case of the males, six to eight years in the case of the females, the well-grown fishes, perhaps a foot and a half to two feet long, are seized by a novel restlessness. They are beginning to be mature. They put on a silvery jacket and become large of eye, and they return to the sea. In getting away from the pond it may be necessary to wriggle through the damp meadow-grass before reaching the river. They travel by night, and rather excitedly. The Arctic Ocean is too cold for them, and the North Sea too shallow. They must go far out to sea, to where the old margin of the once larger continent of Europe slopes down to the great Abysses from the Hebrides southwards. Eels seem to spawn in the deep dark water, but the just liberated eggs have not yet been found. The young fry rises to near the surface and becomes a knife-blade-like larva, transparent all but its eye. It lives for many months in this state, growing to be about three inches long, rising and sinking in the water and swimming gently. These open-sea young eels are known as Leptisephalae, a name given to them before their real nature was proved. They gradually become shorter, and the shape changes from knife-blade-like to cylindrical. During this change they fast, and the weight of their delicate body decreases. They turn into glass eels about two-and-a-half inches long, like a knitting needle in girth. They begin to move towards the distant shores and rivers, and they may be a year-and-a-half all before they reach their destination and go upstream as elvers. Those that ascend the rivers of the eastern Baltic must have journeyed 3,000 miles. It is certain that no eel ever matures or spawns in fresh water. It is practically certain that all the young eels ascending the rivers of North Europe have come in from the Atlantic, some of them perhaps from the Azores or further out still. It is interesting to inquire how the young eels circumvent the falls of the Rhine and get into Lake Constance, or how their kindred on the other side of the Atlantic overcome the obstacle of Niagara, but it is more important to lay emphasis on the variety of habitats which this fish is trying—the deep waters, the open sea, the shore, the river, the pond, and even it may be a little taste of solid earth. It seems highly probable that the common eel is a deep water marine fish which has learned to colonize the fresh waters. It has been adventurous and it is succeeded. The only shadow on the story of achievement is that there seems to be no return from the spawning. There is little doubt the death is the nemesis of their reproduction. In any case, no adult eel ever comes back from the deep sea. We are minded of Girthy's hard saying. Death is nature's expert advice to get plenty of life. Forming New Habits There is a well-known mudfish of Australia, Neociratotus by name, which has turned its swim-bladder into a lung and comes to the surface to spout. It expels vitiated air with considerable force and takes fresh gulps. At the same time, like an ordinary fish, it has gills which allow the usual interchange of gases between the blood and the water. Now this Australian mudfish, or double-breeder, Dipnoan, which may be a long way over a yard in length, is a direct and little-changed descendant of an ancient extinct fish, Ciratotus, which lived in Mesozoic times, as far back as the Jurassic, which probably means over five millions of years ago. The Queensland mudfish is an antiquity, and there has not been much change in its lineage for millions of years. We might take it as an illustration of the inertia of evolution. And yet, though its structure has changed but little, the fish probably illustrates evolution in process, for it is a fish that is learning to breathe dry air. It cannot leave the water, but it can live comfortably in pools which are foul with decomposing animal and vegetable matter. In partially dried up and foul water-holes, full of dead fishes of various kinds, Neociratotus has been found vigorous and lively. Unless we take the view, which is possible, that the swim-bladder of fishes was originally a lung, the mudfishes are learning to breathe dry air. They illustrate evolution agoing. The herring-gull is by nature a fish-heater, but of recent years in some parts of Britain it has been becoming in the summer months more and more of a vegetarian, scooping out the turnips, devouring potatoes, settling on the sheaves in the harvest field and gorging itself with grain. Similar experiments, usually less striking, are known in many birds, but the most signal illustration is that of the Kia, or Nestor parrot, of New Zealand, which is taken to lighting on the loyans of the sheep, tearing away the fleece, cutting at the skin and gouging out fat. Now the parrot belongs to a vegetarian or frugivorous stock, and this change of diet in the relatively short time since sheep ranches were established in New Zealand is very striking. Here, since we know the dates, we may speak of evolution going on under our eyes. It must be remembered that variations in habit may give an animal a new opportunity to test variations in structure, which rise mysteriously from within, as expressions of germinal changefulness rather than as imprints from without. For of the transmissibility of the latter there is little secure evidence. Experiments in Locomotion It is very interesting to think of the numerous types of locomotion which animals have discovered, pulling and punting, sculling and rowing, and of the changes that are rung on these four main methods. How striking is the case of the frilled lizard, Clematosaurus, of Australia, which of the present time is, as it were, experimenting in biopetal progression. Always a rather eventful thing to do. It gets up on its hind legs and runs totteringly for a few feet, just like a baby learning to walk. How beautiful is the adventure which has led to our dipper or water oozle, a bird allied to the wrens, to try walking and flying underwater. How admirable is the vault-planning of numerous parachutists, flying fish, flying frog, flying dragon, flying phalanger, flying squirrel, and more besides, which take great leaps through the air. Or are these not the splendid failures that might have succeeded in starting new modes of flight? Most daring of all, perhaps, are the aerial journeys undertaken by many small spiders. On a breezy morning, especially in the autumn, they mount on gate posts and palings and herbage, and standing with their head to the wind, pay out three or four long threads of silk. When the wind tugs at these threads, the spinners let go and are born, usually back downwards, on the winds of the wind from one parish to another. It is said that if the wind falls they can unfurl more sail, or furl if it rises. In any case, these wingless creatures make aerial journeys. When tens of thousands of used threads sink to the earth, there is a shower of gossamer. On his beagle voyage Darwin observed that fast numbers of small gossamer spiders were born on to the ship when it was sixty miles distant from the land. NEW DEVICES It is impossible, we must admit, to fix dates, except in a few cases, relatively recent, but there is a smack of modernity in some striking devices which we can observe in operation today. Thus no one will dispute the statement that spiders are thoroughly terrestrial animals breathing dry air, but we have the fact that the water spider conquering the underwater world. There are a few spiders about the seashore, and a few that can survive douching with fresh water, but the particular case of the true water spider, Argyranetonatans, stands by itself because the creature, as regards the female at least, has conquered the sub-aquatic environment. A flatish web is woven somehow underneath the water and pegged down by threads of silk. Along a special vertical line the mother spider ascends to the surface and descends again, having entangled air in the hairs of her body. She brushes off this air underneath her web, which is thereby buoyed up into a sort of dome. She does this over and over again, never getting wet all the time, until the domed web has become like a diving bell full of dry air. In this eloquent anticipation of man's rational device, this creature, far from being endowed with reason, lays her eggs and looks after her young. The general significance of the facts is that when competition is keen, a new area of exploitation is a promised land. Thus spiders have spread over all the earth except the polar areas. But here is a spider with some spirit of adventure, which is endeavored, instead of trekking, to find a new corner near at home. It has tackled a problem surely difficult for a terrestrial animal, the problem of living in great part under water, and it has solved it in a manner at once effective and beautiful. In conclusion. We have given but a few representative illustrations of a great theme. When we consider the changefulness of living creatures, the transformations of cultivated plants and domesticated animals, the gradual alterations in the fauna of a country, the search after many haunts, the forming of new habits, and the discovery of many inventions, are we not convinced that evolution is going on? And why should it stop? End of chapter 7 Part 1 of the Outline of Science This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer, please visit LibriVox.org. This recording is by Mark Smith of Simpsonville, South Carolina. The Outline of Science, Volume 1 by J. Arthur Thompson Chapter 7 The Dawn of Mind In the story of evolution there is no chapter more interesting than the emergence of mind in the animal kingdom. But it is a difficult chapter to read, partly because mind cannot be seen or measured, only inferred from the outward behavior of the creature, and partly because it is almost impossible to avoid reading ourselves into the much simpler animals. Two extremes to be avoided. The one extreme is that of uncritical generosity which credits every animal, like Brer Rabbit, who by the way was the hare, with human qualities. The other extreme is that of thinking of the animal as if it were an automatic machine, in the working of which there is no place or use for mind. Both these extremes are to be avoided. When Professor Whitman took the eggs of the passenger pigeon, which became extinct not long ago with startling rapidity, and placed them a few inches to one side of the nest, the bird looked a little uneasy and put her beak under her body as if to feel for something that was not there. But she did not try to retrieve her eggs close at hand as they were. In a short time she flew away altogether. This shows that the mind of the pigeon is in some respects very different from the mind of man. On the other hand, when a certain clever dog, carrying a basket of eggs with the handle in his mouth, came to a style which had to be negotiated. He laid the basket on the ground, pushed it gently through a low gap to the other side, and then took a running leap over. We dare not talk of this dog as an automatic machine. A caution in regard to instinct. In studying the behavior of animals, which is the only way of getting at their mind, for it is only of our own mind that we have direct knowledge, it is essential to give prominence to the fact that there has been throughout the evolution of living creatures a strong tendency to inregister or ingrain capacities of doing things effectively. Thus certain abilities come to be imborn. They are parts of the inheritance, which will express themselves whenever the appropriate trigger is pulled. The newly born child is not required to learn its breathing movements, as it afterwards requires to learn its walking movements. The ability to go through the breathing movements is inborn and grained and registered. In other words, there are hereditary prearrangements of nerve cells and muscle cells, which come into activity almost as readily as the beating of the heart. In a minute or two, the newborn pigling creeps close to its mother and sucks milk. It has not to learn how to do this any more than we have to learn to cough or sneeze. Thus animals have many useful, ready made, or almost ready made, capacities of doing apparently clever things. In several cases of these inborn or prearrangements, we speak of reflex actions, in more complicated cases of instinctive behavior. Now the caution is this, that while these inborn capacities usually work well in natural conditions, they sometimes work badly when the ordinary routine is disturbed. We see this when a pigeon continues sitting for many days on an empty nest, or when it fails to retrieve its eggs only two inches away. But it would be a mistake to call the pigeon, because of this, an unutterably stupid bird. We have only to think of the achievements of homing pigeons to know that this cannot be true. We must not judge animals in regard to those kinds of behavior which have been handed over to instinct, and go badly a G when the normal routine is disturbed. In 99 cases out of 100 the unregistered instinctive capacities work well, and the advantage of their becoming stereotyped was to leave the animal more free for adventures at a higher level. Being a slave of instinct may give the animal a security that enables it to discover some new home or new food or new joy. Somewhat in the same way a man of methodical habits which he has himself established may gain leisure to make some new departure of racial profit. When we draw back our finger from something very hot, or shut our eye to avoid a blow from a rebounding branch, we do not will the action, and this is more or less the case, probably, when a young mammal sucks its mother for the first time. Some mound birds of celibies lay their eggs in warm volcanic ash by the shore of the sea. Others in a great mass of fermenting vegetation. It is inborn in the newly hatched bird to struggle out as quickly as it can from such a strange nest else it will suffocate. If it stops struggling too soon it perishes, for it seems that the trigger of the instinct cannot be pulled twice. Similarly, when the eggs of the turtle that have been laid in the sand of the shore hatch out, the young ones make instinctively for the sea. Some of the crocodiles bury their eggs two feet or so below the surface among sadden and decaying vegetation. An awkward situation for a birth place. When the young crocodile is ready to break out of the eggshell, just as a chick does at the end of the three weeks of brooding, it others instinctively a piping cry. On hearing this the watchful mother digs away the heavy blankets, otherwise the young crocodile will be buried alive at birth. Now there is no warrant for believing that the young mound birds, young crocodiles, and young turtles have an intelligent appreciation of what they do when they are hatched. They act instinctively, as to the man are born. But this is not to say that their activity is not backed by endeavor or even suffused with a certain amount of awareness. Of course, it is necessarily difficult for man who is so much a creature of intelligence to get even an inkling of the mental side of instinctive behavior. In many of the higher reaches of animal instinct, as in courtship or nest building, in hunting or preparing the food, it looks as if the starting of the routine activity also rang up the higher centers of the brain and put the intelligence on the kiviv, ready to interpose when needed. So the twofold caution is this. One, we must not depreciate the creature too much if, in unusual circumstances, it acts in an ineffective way along lines of behavior which are normally handed over to instinct. And two, we must leave open the possibility that even routine instinctive behavior may be suffused with awareness and backed by endeavor. A useful law. But how are we to know when to credit the animal with intelligence and when with something less spontaneous? Above all, how are we to know when the effective action, like opening the mouth the very instant it is touched by food in the mother's beak, is just a physiological action like coughing or sneezing, and when there is behind it a mind at work? The answer to this question is no doubt that, given by Professor Lloyd Morgan, who may be called the founder of comparative psychology, that we must describe the piece of behavior very carefully, just as it occurred, without reading anything into it, and that we must not ascribe it to a higher faculty if it can be satisfactorily accounted for in terms of a lower one. In following this principle we may be sometimes niggardly, for the behavior may have a mental subtlety that we have missed. But in nine cases out of ten our conclusions are likely to be sound. It is the critical, scientific way. Bearing this law in mind, let us take a survey of the emergence of mind among backboneed animals. Censors of Fishes Fishes cannot shut their eyes, having no true lids, but the eyes themselves are very well developed, and the vision is acute, especially for moving objects. Except in gristly fishes, the external opening to the ear has been lost, so that sound waves and coarser vibrations must influence the inner ear, which is well developed, through the surrounding flesh and bones. It seems that the main use of the ear in fishes is in connection with balancing, not with hearing. In many cases, however, the sense of hearing has been demonstrated. Thus fishes will come to the side of a pond to be fed when a bell is rung, or when a whistle is blown by someone not visible from the water. The fact that many fishes pay no attention at all to loud noises does not prove that they are deaf, for an animal may hear a sound and yet remain quite indifferent or irresponsive. This merely means that the sound has no vital interest for the animal. Some fishes, such as bullhead and dogfish, have a true sense of smell, detecting by their nostrils very dilute substances permeating the water from a distance. Others, such as members of the cod family, perceive their food in part at least by the sense of taste, which is susceptible to substances near at hand and present in considerable quantity. This sense of taste may be located on the fins as well as about the mouth. At this low level the senses of smell and taste do not seem to be very readily separated. The chief use of the sensitive line or lateral line seen on each side of a bony fish is to make the animal aware of slow vibrations and changes of pressure in the water. The skin responds to pressures, the ear to vibrations of high frequency. The lateral line is between the two in its function. The brain of the ordinary bony fish is at a very low level. Thus the cerebral hemispheres, destined to become more and more the seat of intelligence, are poorly developed. In gristly fishes, like skates and sharks, the brain is much more promising. But although the state of the brain does not lead one to expect very much from a bony fish like trout or eel, haddock or herring, illustrations are not wanting of what might be called pretty pieces of behavior. Let us select a few cases. The Stickleback's Nest The three-spined and two-spined sticklebacks live equally well in fresh or salt water. The larger fifteen-spined stickleback is entirely marine. In all three species the male fish makes a nest. In fresh or brackish water, in the first two cases, in shore pools, in the third case. The little species use the leaves and stems of water-plants. The larger species use seaweed and zoophyte. The leaves or fronds are entangled together and fastened by glue-like threads, secreted, strange to say, by the kidneys. It is just as if a temporary disease condition had been regularized and turned to good purpose. Going through the nest several times, the male makes a little room in the middle. Partly by coercion and partly by coaxing, he induces a female, first one and then another, to pass through the nest with two doors, depositing eggs during her short sojourn. The females go their way, and the male mounts guard over the nest. He drives off intruding fishes much bigger than himself. When the young are hatched, the male has for a time much to do, keeping his charges within bounds until they are able to move about with agility. It seems that sticklebacks are short-lived fishes, probably breeding only once, and it is reasonable to suppose that their success as a race depends to some extent on the paternal care. Now if we could believe that the nesting behavior had appeared suddenly in its present form, we should be inclined to credit the fish with considerable mental ability. But we are less likely to be so generous if we reflect that the routine has been, in all likelihood, the outcome of a long racial process of slight improvements and critical testings. The secretion of the glue probably came about as a pathological variation. Its utilization was perhaps discovered by accident. The types that had wit enough to take advantage of this were most successful. The routine became in-registered hereditarily. The stickleback is not so clever as it looks. To find solid ground on which to base an appreciation of the behavior of fishes, it is necessary to experiment, and we may refer to Miss Gertrude White's interesting work on American minnows and sticklebacks. After the fishes had become quite at home in their artificial surroundings, their lessons began. Cloth-packets, one of which contained meat and the other cotton, were suspended at opposite ends of the aquarium. The mud-minnows did not show that they perceived either packet, though they swam close by them. The sticklebacks were intrigued at once. Those that went towards the packet containing meat darted furiously upon it and pulled at it with great excitement. Those that went towards the cotton packet turned sharply away when they were within about two inches off. They then perceived what those at the other end were after and joined them, a common habit amongst fishes. Although the minnows were not interested in the tiny bags of mystery, they were even more alert than the sticklebacks in perceiving moving objects in or on the water, and there is no doubt that both these shallow water species discovered their food largely by sense of sight. The next set of lessons had to do with color associations. The fishes were fed on minced snail, chopped earthworm, fragments of liver, and the like, and the food was given to them from the end of forceps held above the surface of the water, so that the fishes could not be influenced by smell. They had to leap out of the water to take the food from the forceps. Disks of colored cardboard were slipped over the end of the forceps, so that what the fishes saw was a morsel of food in the center of a colored disk. After a week or so of preliminary training they were so well accustomed to the colored disks that the presentation of one served as a signal for the fishes to dart to the surface and spring out of the water. When baits of paper were substituted for the food, the fishes continued to jump at the disks. When, however, a blue disk was persistently used for the paper bait, and a red disk for the real food, or vice versa, some of the minnows learned to discriminate infallibly between shadow and substance, both when these were presented alternately and when they were presented simultaneously. This is not far from the dawn of mind. In the course of a few lessons both minnows and stickle-backs learned to associate particular colors with food, and other associations were also formed. A kind of larva that a minnow could make nothing of after repeated trials was subsequently ignored. The approach of the experimenter or anyone else soon began to serve as a food signal. There can be no doubt that in the ordinary life of fishes there is a process of forming useful associations and suppressing useless responses. Given an inborn repertory of profitable movements that require no training, given the power of forming associations such as those we have illustrated, and given a considerable degree of sensory alertness along certain lines, fishes do not require much more. And in truth they have not got it. Moving with great freedom in three dimensions and a medium that supports them and is very uniform and constant, able in most cases to get plenty of food without fatiguing exertions and to dispense with it for considerable periods, if it is scarce, multiplying usually in great abundance so that the huge infantile mortality hardly counts. Rarely dying a natural death, but usually coming with their strength unabated to a violent end, fishes hold their own in the struggle for existence without much in the way of mental endowment. Their brain has more to do with motion than with mentality, and they have remained at a low psychical level. Yet just as we should greatly misjudge our own race if we confined our attention to everyday routine, so in our total, as distinguished from our average estimate of fishes, we must remember the salmon surmounting the falls, the weary trout eluding the angler's skill, the common mudskipper periothalmos of many tropical shores which climbs on the rocks and the roots of the mangrove trees, or actively hunts small shore animals. We must remember the adventurous life history of the eel, and the quaint ways in which some fishes, males especially, look after their family. The male sea-horse puts the eggs in his breast-pocket. The male Curtis carries them on the top of his head. The cock-patle, or lump-sucker, guards them and aerates them in a corner of a shore-pool. The Mind of Amphibians Towards the end of the age of the old red sandstone, or Devonian, a great step in evolution was taken—the emergence of amphibians. The earliest representatives had fish-like characters even more marked than those which may be discerned in the tadpoles of our frogs and toads, and there was no doubt that amphibians sprang from a fish-stock. But they made great strides, associated in part with their attempts to get out of the water on to dry land. From fossil forms we cannot say much in regard to soft parts, but if we consider the living representatives of the class, we may credit amphibians with such important acquisitions as fingers and toes, a three-chambered heart, true ventral lungs, a drum to the ear, a mobile tongue, and vocal cords. When animals began to be able to grasp an object, and when they began to be able to utter sufficient sounds, two new doors were opened. Apart from insects, whose instrumental music had probably begun before the end of the Devonian age, amphibians were the first animals to have a voice. The primary meaning of this voice was doubtless, as it is today in our frogs, a sex-call, but it was the beginning of what was destined to play a very important part in the evolution of the mind. In the course of ages the significance of the voice broadened out. It became a parental call. It became an infant's cry. Broadening still, it became a very useful means of recognition among kindred, especially in the dark and in the intricacies of the forest. Ages passed, and the voice rose on another turn in the evolutionary spiral to be expressive of particular emotions beyond the immediate circle of sex. Emotions of joy and of fear, of jealousy and of contentment. Finally, we judged the animal. Perhaps the bird was first, began to give utterance to particular words, indicative not merely of emotions, but of particular things with an emotional halo, such as food, enemy, home. Long afterwards word became in man the medium of reasoned discourse. Emotions were made and judgements expressed, but was not the beginning in the croaking of amphibia? Senses of Amphibians Frogs have good eyes, and the toad's eyes are jewels. There is evidence of precise vision in the neat way in which a frog catches a fly, flicking out its tongue, which is fixed in front and loose behind. There is also experimental proof that a frog discriminates between red and blue or between red and white, and an interesting point is that while our skin is sensitive to heat rays but not to light, the skin of the frog answers back to light rays as well. Professor Yerks experimented with a frog which had to go through a simple labyrinth if it wished to reach a tank of water. At the first alternative between two paths, a red card was placed on the wrong side and a white one on the other. When the frog had learned to take the correct path, marked by the white card, Professor Yerks changed the cards. The confusion of the frog showed how thoroughly it had learned its lesson. We know very little in regard to sense of smell or taste in amphibians, but the sense of hearing is well developed. More developed than might be inferred from the indifference that frogs show to almost all sounds except the croaking of their kindred and splashes in the water. The toad looks almost sagacious when it is climbing up a bank and some of the tree frogs are very alert, but there is very little that we dare say about the amphibian mind. We have mentioned that frogs may learn the secret of a simple maze, and toads sometimes make for a particular spawning-pond from a considerable distance, but an examination of their brains, occupying a relatively small part of the broad, flat skull, warns us not to expect much intelligence. On the other hand, when we take frogs along a line that is very vital to them, namely the discrimination of palatable and unpalatable insects, we find by experiment that they are quick to learn and that they remember their lessons for many days. Frogs sometimes deposit their eggs in very unsuitable pools of water, but perhaps that is not quite so stupid as it looks. The egg laying as a matter which has been, as it were, handed over to instinctive registration. Experiments in Parental Care It must be put to the credit of amphibians that they have made many experiments in methods of parental care as if they were feeling their way to new devices. A common frog lays her clumps of eggs in the cradle of the water, sometimes far over a thousand together. The toad winds two long strings rounded between waterweeds, and in both cases that is all. There is no parental care, and the prolific multiplication covers the enormous infantile mortality. This is the spawning solution of the problem of securing the continuance of the race. But there is another solution that a parental care associated with an economical reduction of the number of eggs, thus the male of the nursefrog, Alites, not uncommon on the continent, fixes a string of twenty to fifty eggs to the upper part of his hind legs and retires to his hole, only coming out at night to get some food and to keep up the moisture about the eggs. In three weeks, when the toad-polls are ready to come out, he plunges into the pond in his freed from his living burden and his family cares. In the case of the thoroughly aquatic Surinam toad, Pipa, the male helps to press the eggs, perhaps a hundred in number, on to the back of the female, where each sinks into a pocket of skin with a little lid. By and by fully-formed young toads jump out of the pockets. In the South American tree-frogs called nutotrima, there is a pouch on the back of the female in which the eggs develop, and it's interesting to find that in some species what come out are ordinary tad-polls, while in other species the young emerge as miniatures of their parents. Strangest of all, perhaps, is the case of Darwin's dog, Rhino-derma of Chile, where the young, about ten to fifteen in number, develop in the male's croaking sacs, which become in consequence enormously distended. Eventually the strange spectacle is seen of miniature frogs jumping out of their father's mouth. Needless to say we are not citing these methods of parental care as examples of intelligence, but perhaps they correct the impression of amphibians as a rather humdrum race. Never be the mental aspect of the facts. There has certainly been some kind of experimenting, and the increase of parental care, so marked in many amphibians, with associated reduction of the number of offspring, is a finger-prost on the path of progress. The Reptilian Mind We speak of the wisdom of the serpent, but it is not very easy to justify the phrase. Among all the multitude of reptiles, snakes, lizards, turtles, and crocodiles, a motley crowd, we cannot see much more than occasional traces of intelligence. The inner life remains a tiny rill. No doubt many reptiles are very effective, but is an instinctive rather than an intelligent efficiency. The well-known soft-shelled tortoise of the United States swims with powerful strokes and runs so quickly that it can hardly be overtaken. It hunts vigorously for crayfish and insect larvae in the rivers. It buries itself in the mud when cold weather comes. It may lie on a floating log ready to slip into the water at a moment's notice. It may bask on a sunny bank or in the warm shallows. Great wariness is shown in choosing times and places for egg-laying. The mother tramps the earth down upon the buried eggs. All is effective. Similar statements might be made in regard to scores of other reptiles, but what we see is almost wholly of the nature of instinctive routine, and we get little glimpse of more than efficiency and endeavour. In a few cases there is proof of reptiles finding their way back to their homes from a considerable distance, and recognition of persons is indubitable. Gilbert White remarks of his tortoise, Whenever the good old lady came in sight who had waited on it for more than thirty years, it always hobbled with awkward alacrity towards its benefactress, while to strangers it was altogether inattentive. Of definite learning there are a few records. Thus Professor Yerks studied a sluggish turtle of retiring disposition, taking advantage of its strong desire to efface itself. On the path of the darkened nest of damp grass he interposed a simple maze in the form of a partitioned box. After wandering about constantly for thirty-five minutes the turtle found its way through the maze by chance. Two hours afterwards it reached the nest in fifteen minutes, and after another interval of two hours it only required five minutes. After the third trial the routes became more direct, there was less aimless wandering. The time of the twentieth trial was forty-five seconds, that of the thirtieth forty seconds. In the thirtieth case the path followed was quite direct, and so it was on the fiftieth trip which only required thirty-five seconds. Of course the whole thing did not amount to very much, but there was a definite learning, a learning from experience which has played an important part in the evolution of animal behavior. Comparing reptiles with amphibians we may recognize an increased masterliness of behavior and a hint of greater plasticity. The records of observers who have made pets of reptiles suggest that the life of feeling or emotion is growing stronger, and so do stories, if they can be accepted, which suggest the beginning of a conjugal affection. The error must be guarded against of interpreting in terms of intelligence what is merely the outcome of long continued structure adaptation. When the limbless lizard called the slow worm is suddenly seized by the tail it escapes by surrendering the appendage which breaks across a preformed, weak plane. But this is a reflex action, not a reflective one. It is comparable to our sudden withdrawal of our finger from a very hot cinder. The egg-eating African snake, Dasipeltis, gets the egg of a bird into its gullet unbroken and cuts the shell against downward projecting sharp points of the vertebrae. None of the precious contents is lost and the broken empties are returned. It is admirable, indeed unsurpassable, but it is not intelligent. Sight and hearing are highly developed in birds, and the senses, besides pulling the triggers of inborn efficiencies, supply the raw materials for intelligence. There is some truth, though not the whole truth, and the old philosophical dictum, that there is nothing in the intellect which was not previously in the senses. Many people have admired the certainty and alacrity with which gulls pick up a fragment of biscuit from the white wake of a steamer, and the incident is characteristic. In their power of rapidly altering the focus of the eye birds are unsurpassed. To the sense of sight in birds the sense of hearing comes a good second. A twig breaks under our feet and out sounds the danger call of the bird we were trying to watch. Many young birds, like partridges, respond when two or three hours old to the anxious warning note of the parents, and squat motionless on the ground, though other sounds, such as the excited clucking of a foster mother hen, leave them indifferent. They do not know what they are doing when they squat. They are obeying the living hand of the past which is within them. Their behavior is instinctive, but the present point is the discriminating quality of the sense of hearing, and that is corroborated by the singing of birds. It is emotional art, expressing feelings in the medium of sound. On the part of the females who are supposed to listen it be tokens a cultivated ear. As to the other senses, touch is not highly developed except about the bill, where it reaches a climax in birds like the woodcock, which probe for unseen earthworms in the soft soil. Taste seems to be poorly developed, for most birds bolt their food, but there is sometimes an emphatic rejection of unpalatable things like toads and caterpillars. Of smell in birds little is known, but has been proved to be present in certain cases, for instance in some nocturnal birds of prey. It seems certain that it is by sight, not by smell, that the eagles gather to the carcass, but perhaps there is more smell in birds than they are usually credited with. One would like to experiment with the oil from the preen gland of birds to see whether the scent of this does not help in the recognition of kin by kin at night or amid the darkness of the forest. There may be other senses in birds such as a sense of temperature and a sense of balance, but no success has attended the attempts made to demonstrate a magnetic sense, which has been impatiently postulated by students of bird migration in order to explain how the birds find their way. The big fact is that in birds there are two widely open gateways of knowledge, the sense of sight and the sense of hearing. INSTINCTIVE APTITUDES Many a young water bird, such as a coot, swims right away when it is tumbled into water for the first time. So chicks peck without any learning or teaching, very young ducklings catch small moths that flit by, and young plovers lie low when the danger signal sounds. But birds seem strangely limited as regards many of these instinctive capacities, limited when compared with the little-brained ants and bees, which have from the first such a rich repertory of ready-made cleverness. The limitation in birds is of great interest, for it means that intelligence is coming to its own and is going to take up the reins at many corners of the daily round. Professor Lloyd Morgan observed that his chickens, incubated in the laboratory, had no instinctive awareness of the significance of their mother's cluck when she was brought outside the door. Although thirsty and willing to drink from a moistened fingertip, they did not instinctively recognize water, even when they walked through a saucer full. Only when they happened to pick their toes as they stood in the water did they appreciate water as the stuff they wanted and raise their bills up to the sky. Once or twice they actually stuffed their crops with worms of red-worsted. Instinctive aptitudes, then, the young birds have, but these are more limited than in ants, bees, and wasps, and the reason is to be found in the fact that the brain is now evolving on the tack of what Sir Ray Lancaster has called educability. Young birds learn with prodigious rapidity the emancipation of the mind from the tyranny of hereditary obligations has begun. Young birds make mistakes, like the red-worsted mistake, but they do not make the same mistakes often. They are able to profit by experience in a very rapid way. We do not mean the creatures of the little-brained type, like ants, bees, and wasps, are unable to profit by experience or are without intelligence. There are no such hard and fast lines. We mean that in the ordinary life of insects the unregistered instinctive capacities are on the whole sufficient for the occasion, and that intelligent educability is very slightly developed. Nor do we mean that birds are quite emancipated from the tyranny of ingrained instinctive obligations and can always ring up intelligence in a way that is impossible for the stereotype to be. The sight of a pigeon brooding on an empty nest while her two eggs lie disregarded only a couple of inches away is enough to show that along certain lines birds may find it impossible to get free from the trammels of instinct. The peculiar interest of birds is that they have many instincts and yet a notable power of learning intelligently. Intelligence Cooperating with Instinct Professor Lloyd Morgan was foster parent to two morehands which grew up in isolation from their kindred. They swam instinctively, but they would not dive, neither in a large bath nor in a current. But it happened one day when one of these morehands was swimming in a pool on a Yorkshire stream that a puppy came barking down the bank and made an awkward faint towards the young bird. In a moment the morehands dived, disappeared from view, and soon partially reappeared, his head just peeping above the water beneath the overhanging bank. This was the first time the bird had dived, and the performance was absolutely true to type. There can be little doubt as to the meaning of this observation. The morehands has an hereditary or instinctive capacity for swimming and diving, but the latter is not so easily called into activity as the former. The particular morehands in question had enjoyed about two months of swimming experience, which probably counted for something, but in the course of that experience nothing had pulled the trigger of the diving capacity. On an eventful day the young morehands saw and heard the dog, it was emotionally excited, it probably did to an extent intelligently appreciate a novel and meaningful situation. Intelligence cooperated with instinct, and the bird dived appropriately. Birds have inborn predispositions to certain effective ways of pecking, scratching, swimming, diving, flying, crouching, lying low, nest building and so on, but they are marked off from the much more purely instinctive ants and bees by the extent to which individual nurture seems to mingle with the inherited nature. The two together result in the fine product which we call the bird's behavior. After Lloyd Morgan's chicks had tried a few conspicuous and unpalatable caterpillars, they had no use for any more. They learned in their early days with prodigious rapidity, illustrating the deep difference between the big brain type, relatively poor in its endowment of instinctive capacities, but eminently educable, and the little brain type, say of ants and bees, richly endowed with instinctive capacities, but very far from being quick or glad to learn. We owe it to Sir Ray Lancaster to have made it clear that these two types of brain are, as it were, on different tax of evolution and should not be directly pitted against one another. The little brain type makes for a climax in the ant, where instinctive behavior reaches a high degree of perfection. The big brain type reaches its climax in horse and dog, in elephant and monkey. The particular interest that attaches to the behavior of birds is in the combination of a good deal of instinct with a good deal of intelligent learning. This is well illustrated when birds make a nest out of new materials or in some quite novel situation. It is clearly seen when birds turn to some new kind of food, like the Kia parrot, which attacks the sheep in New Zealand. Some young woodpeckers are quite clever in opening fur cones to get at the seeds, and this might be hastily referred to a well- defined hereditary capacity. But the facts are that the parents bring their young ones first the seeds themselves, then partly open cones, and then intact ones. There is an educative process, and so it is in scores of cases. Using Their Whits When the Greek eagle lifts the Greek tortoise in its talons and lets it fall from a height so that the strong carapace is broken and the flesh exposed, it is making intelligent use of an expedient. Where it discovered the expedient by experimenting, as is possible, or by chance, as is more likely, it uses it intelligently, in the same way herring gulls lift sea urchins and clams in their bills and let them fall on the rocks so that the shells are broken. In the same way, rooks deal with freshwater mussels. The Thrushes and Bill A very instructive case is the behavior of the song thrush when it takes a wood snail in its beak and hammers it against a stone, its so-called anvil. To a young thrush, which she had brought up by hand, Miss Francis Pitt offered some wood snails, but it took no interest in them until one put out its head and began to move about. The bird then pecked at the snail's horns but was evidently puzzled when the creature retreated within the shelter of the shell. This happened over and over again. The thrush's inquisitive interest increasing day by day. It pecked at the shell and even picked it up by the lip, but no real progress was made till the sixth day when the thrush seized the snail and beat it on the ground as it would a big worm. On the same day it picked up a shell and knocked it repeatedly against a stone, trying first one snail and then another. After fifteen minutes' hard work, the thrush managed to break one, and after that it was all easy. A certain predisposition to beat things on the ground was doubtless present, but the experiment showed that the use of an anvil could be arrived at by an untutored bird. After prolonged trying it found out how to deal with a difficult situation. It may be said that in more natural conditions this might be picked up by imitation, but while this is quite possible it is useful to notice that experiments with animals lead us to doubt whether imitation counts for nearly so much as used to be believed. THE MIND OF THE MAMMEL When we watch a collie at a sheep-driving competition, or an elephant helping the forester, or a horse shunting wagons at a railway siding, we are apt to be too generous to the mammal mind, for in the cases we have just mentioned part of man's mind has, so to speak, got into the animals. On the other hand when we study rabbits and guinea pigs we are apt to be too stingy, for these rodents are under the average of mammals, and those that live in domestication illustrate the stupefying effect of a too-sheltered life. The same applies to domesticated sheep contrasted with wild sheep, or even with their own lambs. If we are to form a sound judgment on the intelligence of mammals we must not attend too much to those that have profited by man's training, nor to those whose mental life has been dulled by domestication. INSTINCTIVE APTITOUS What is to be said of the behavior of beavers who gnaw the base of a tree with their chisel-edged teeth till only a narrow core is left to snap in the first gale bringing the useful branches down to the ground? What is to be said of the harvest-moust, constructing its nest, or of the squirrel-making cache after cache of nuts? These and many similar pieces of behavior are fundamentally instinctive, due to embore and predispositions of nerve cells and muscle cells. But in mammals they seem to be often attended by a certain amount of intelligent attention, saving the creature from the tyranny of routine so marked in the ways of ants and bees. SHEAR DEXTERITY Besides instinctive aptitudes, which are exhibited in almost equal perfection by all members of the same species, there are acquired dexterities which depend on individual opportunities. They are also marked by being outside and beyond ordinary routine, not that any rigorous boundary line can be drawn. We read that at Mathura on the Jumna, doles of food are provided by the piety of pilgrims for the sacred river tortoises, which are so crowded when there is food going that their smooth carapaces form a more or less continuous raft across the river. On that unsteady slippery bridge delanger monkeys, some notpithecus entilus, venture out, and in spite of vicious snaps secure a share of the booty. This picture of the monkeys securing a footing on the moving mass of turtle-backs is almost a diagram of sheer dexterity. It illustrates the spirit of adventure, the will to experiment, which is, we believe, the main mode of force and new departures in behavior. A bull terrier called Jasper, studied by Professor J.B. Watson, showed great power in associating certain words with certain actions. From a position invisible to the dog the owner would give certain commands such as, go into the next room and bring me a paper lying on the floor. Jasper did this at once, and a score of similar things. Lord Avebury's dog Van was accustomed to go to a box containing a small number of printed cards and select the card T, or out, as the occasion suggested. It had established an association between certain black marks on a white background and the gratification of certain desires. It is probable that some of the extraordinary things horses and dogs have been known to do in the way of stamping a certain number of times in supposed indication of an answer to an arithmetical question, in the case of horses, or of the name of an object drawn, in the case of dogs, are depended on clever associations established by the teacher between minute signs and a number of stampings. What is certain is that mammals have, in varying degrees, a strong power of establishing associations. There is often some delicacy in the association established. Everyone knows of cases where a dog, a cat, or a horse will remain quite uninterested to all appearance in its owner's movements until some little detail, such as taking a key from its peg, pulls the trigger. Now the importance of this in the wild life of the fox or the hare, the otter or the squirrel, is obviously that the young animals learn to associate certain sounds in their environment with definite possibilities. They have to learn an alphabet of woodcraft, the letters of which are chiefly sounds and scents. The Dancing Mouse as a Pupil The Dancing or Waltzing Mouse is a Japanese variety with many peculiarities, such as having only one of the three semicircular canals of the ear well developed. It has a strong tendency to waltz around and round in circles, without sufficient cause, and to trip sideways towards its dormitory instead of proceeding in the orthodox head-on fashion. But this freak is a very educable creature, as Professor Yerks has shown. In a careful way he confronted his mouse pupil with alternative pathways marked by different degrees of illumination, or by different colors. If the mouse chose compartment A, it found a clear passage direct to its nest. If it chose compartment B, it was punished by a mild electric shock, and it had to take a roundabout road home. Needless to say, the A compartment was sometimes to the right hand, sometimes to the left, else mere position would have been a guide. The experiments show that the Dancing Mice learned to discriminate the right path from the wrong, and similar results have been got from other mammals, such as rats and squirrels. There is no proof of learning by ideas, but there is proof of learning by experience, and the same must be true in wild life. Many mammals, such as cats and rats, learn how to manipulate puzzle boxes, and how to get at the treasure at the heart of a Hampton Court maze. Some of the puzzle boxes, with a reward of food inside, are quite difficult, for the various bolts and bars have to be dealt with in a particular order, and yet many mammals master the problem. What is plain is that they gradually eliminate useless movements, that they make fewer and fewer mistakes, that they eventually succeed, and that they register the solution within themselves so that it remains with them for a time. It looks a little like the behavior of a man who learns a game of skill without thinking. It is a learning by experience, not by ideas or reflection. Thus, it is very difficult to suppose that a rat or a cat could form any idea or even picture of the Hampton Court maze, which they nevertheless master. Learning Tricks In sufficient inducement many of the cleverer mammals will learn to do very sensible things, and no one is wise enough to say that they never understand what they are doing. Yet it is certain that trained animals often exhibit pieces of behavior which are not nearly so clever as they look. The elephant at the Bellevue Gardens in Manchester used to collect pennies from benevolent visitors. When it got a penny in its trunk, it put it in the slot of an automatic machine which delivered up a biscuit. When a visitor gave the elephant a half-penny, it used to throw it back with disgust. At first sight this seemed almost wise, and there was no doubt some intelligent appreciation of the situation, but it was largely a matter of habituation, the outcome of careful and prolonged training. The elephant was laboriously taught to put the penny in the slot and to discriminate between the useful pennies and the useless half-pennies. It was not nearly so clever as it looked. Using their Wits In the beautiful zoological part in Edinburgh the polar bear was want to sit on a rocky peninsula of a water-filled quarry. The visitors threw in buns, some of which floated on the surface. It was often easy for the polar bear to collect half a dozen by plunging into the pool, but it had discovered a more interesting way. At the edge of the peninsula it scooped the water gently with its huge paw and made a current which brought the buns ashore. This was a simple piece of behavior, but it has the smack of intelligence of putting two and two together in a novel way. It suggests the power of making what is called a perceptual inference. On the occasion of a great flood in a meadow it was observed that a number of mares brought their foals to the top of a knoll and stood round about them protecting them against the rising water. A dog has been known to show what was at any rate a plastic appreciation of a varying situation in swimming across a tidal river. It changed its starting point, they say, according to the flow or ebb of the tide. Arctic foxes and some other wild mammals show great cleverness in dealing with traps, and the manipulative intelligence of elephants is worthy of all our admiration. End of Part 1 of this chapter