 Section 6 of The Outline of Science, Volume 1. The Outline of Science, Volume 1 by J. Arthur Thomson. Section 6. Part 3. Adaptations to Environment. We saw in a previous chapter how the process of evolution led to a mastery of all the haunts of life. But it is necessary to return to these haunts or homes of animals in some detail, so as to understand the peculiar circumstances of each, and to see how in the course of ages of struggle all sorts of self-preserving and race-continuing adaptations or fitnesses have been wrought out and firmly established. Living creatures have spread over all the earth, and in the waters under the earth, some of them have conquered the underground world and others the air. It is possible, however, as has been indicated, to distinguish six great haunts of life, each tenanted by a distinctive fauna, namely the shore of the sea, the open sea, the depths of the sea, the fresh waters, the dry land, and the air. In the deep sea there are no plants at all. In the air the only plants are floating bacteria, though there is a sense in which a tree is very aerial, and the orchid perched on its branches still more so. In the other four haunts there is a flora as well as a fauna, the two working into one another's hands in interesting and often subtle interrelations, the subject of a separate study. The shore of the sea The seaweed area By the shore of the sea the zoologist means much more than the narrow zone between tide-marks. He means the whole of the relatively shallow, well-illumined, seaweed-growing shelf around the continents and continental islands. Technically this is called the littoral area, and it is divisible into zones, each with its characteristic population. It may be noted that the green seaweeds are highest up on the shore. The brown ones come next. The beautiful red ones are lowest. All of them have got green chlorophyll, which enables them to utilize the sun's rays in photosynthesis, i.e. building up carbon compounds from air, water, and salts. But in the brown and red seaweeds the green pigment is masked by others. It is maintained by some botanists that these other pigments enable their possessors to make more of the scantier light in the deeper waters. However this may be we must always think of the shore haunt as the seaweed-growing area. Directly and indirectly the life of the shore animals is closely wrapped up with the seaweeds, which afford food and foothold and temper the force of the waves. The minute fragments broken off from seaweeds and from the seagrass, a flowering plant called Zostera, form a sort of nutritive sea dust which is swept slowly down the slope from the shore to form a very useful deposit in the quietness of deepish water. It is often found in the stomachs of marine animals living a long way offshore. Conditions of shore life The littoral area, as defined, is not a large haunt of life. It occupies only about 9 million square miles, a small fraction of the 197 million of the whole earth's surface. But it is a very long haunt, some 150,000 miles, winding in and out by bay and fjord, estuary and creek. Where deep water comes close to cliffs there may be no shore at all. In other places the relatively shallow water with seaweeds growing over the bottom may extend outwards for miles. The nature of the shore varies greatly according to the nature of the rocks, according to what the streams bring down from inland, and according to the jetsum that is brought in by the tides. The shore is a changeful place, there is in the upper reaches, a striking difference between tide in and tide out. There are vicissitudes due to storms, to freshwater floods, to wind-blown sand, and to slow changes of level up and down. The shore is a very crowded haunt, for it is comparatively narrow, and every niche among the rocks may be precious. Keen struggle for existence It follows that the shore must be the scene of a keen struggle for existence, which includes all the answers back that living creatures make to environing difficulties and limitations. There is struggle for food accentuated by the fact that small items tend to be swept away by the outgoing tide, or to sink down the slope to deep water. Apart from direct competition, e.g. between hungry hermit crabs, it often involves hard work to get a meal. This is true even of apparently sluggish creatures. Thus the crumb-of-bread sponge, or any other seashore sponge, has to lash large quantities of water through the intricate canal system of its body before it can get a sufficient supply of the microscopic organisms and organic particles on which it feeds. An index of the intensity of the struggle for food is afforded by the nutritive chains which bind animals together. The shore is almost noisy with the conjugation of the verb to eat in its many tenses. One pound of rock cod requires for its formation ten pounds of whelk. One pound of whelk requires ten pounds of sea worms, and one pound of worms requires ten pounds of sea dust. Such is the circulation of matter, ever passing from one embodiment or incarnation to another. Besides struggle for food there is struggle for foothold and for fresh air, struggle against the scouring tide and against the pounding breakers. The risk of dislodgement is often great, and the fracture of limbs is a common accident. Of kinds of armour, the sea urchins hedgehog-like test, the crabs shard, the limpets shell, there is great variety, surpassed only by that of weapons, the sea anemones stinging cells, the sea urchins snapping blades, the hermit crabs forceps, the grappling tentacles and parrots beak jaws of the octopus, shifts for a living. We get another glimpse of the intensity of the seashore struggle for existence in the frequency of shifts for a living, adaptations of structure or of behaviour which meet frequently recurrent vicissitudes. The starfish is often in the dilemma of losing a limb or its life. By a reflex action it jenisons the captured arm and escapes. And what is lost is gradually regrown. The crab gets its leg broken past all mending. It casts off the leg across a weak breakage plane near the base and within a preformed bandage which prevents bleeding a new leg is formed in miniature. Such is the adaptive device, more reflex than reflective which is called self-mutilation or autotomy. In another part of this book there is a discussion of camouflaging and protective resemblance. How abundantly these are illustrated on the shore. But there are other shifts for a living. Some of the sandhoppers and their relatives illustrate the puzzling phenomenon of feigning death becoming suddenly so motionless that they escape the eyes of their enemies. Cuttlefishes, by discharging sepia from their ink bags, are able to throw dust in the eyes of their enemies. Some undisguised shore animals, e.g. crabs, are adepts in a hide-and-seek game. Some fishes, like the butterfish or gunnel, escape between stones where there seemed no opening and are almost uncatchable in their slipperiness. Subtleist of all perhaps is the habit some hermit crabs have of entering into mutually beneficial partnership, commensalism, with sea anemones, which mask their bearers and also serve as mounted batteries, getting transport as their reward and likewise crumbs from the frequently spread table. But enough has been said to show that the shore haunt exhibits an extraordinary variety of shifts for a living. Parental care on the shore. According to Darwin, the struggle for existence, as a big fact in the economy of animate nature, includes not only competition, but all the endeavours which secure the welfare of the offspring and give them a good send-off in life. So it is without a jolt that we pass from struggle for food and foothold to parental care. The marine leech, called pontabdella, an interesting greenish warty creature fond of fixing itself to skate, places its egg cocoons in the empty shell of a bivalve mollusk and guards them for weeks, removing any mud that might injure their development. We have seen a British starfish with its fully formed young ones creeping about on its body, though the usual mode of development for shore starfishes is that the young ones pass through a free-swimming larval period in the open water. The father sea-spider carries about the eggs attached to two of his limbs. The father sea-horse puts his mate's eggs into his breast pocket and carries them there in safety until they are hatched. The father stickle-back of the shore-pools makes a seaweed nest and guards the eggs which his wives are induced to lay there. The father lump-sucker mounts guard over the bunch of pinkish eggs which his mate has laid in a nook of a rocky shore-pool and drives off intruders with zest. He also aerates the developing eggs by frequently paddling with his pectoral fins and tail, as the Scots name cock-patle probably suggests. It is interesting that the salient examples of parental care in the shore-hunt are mostly on the male parent's side, but there is maternal virtue as well. The fauna of the shore is remarkably representative from unicellular protozoa to birds like the oyster catcher and mammals like the seals. Almost all the great groups of animals have apparently served an apprenticeship in the shore-hunt and, since lessons learned for millions of years sink in and become organically in-registered, it is justifiable to look to the shore as a great school in which were gained racial qualities of endurance, patience, and alertness. Two. The open sea. In great contrast to the narrow, crowded, difficult conditions of the shore-hunt, littoral area, are the spacious, bountiful, and relatively easy-going conditions of the open sea, pelagic area, which means the well-lighted surface waters is quite away from land. Many small organisms have their maximum abundance at about 50 fathoms so that the word surface is to be taken generously. The light becomes very dim at 250 fathoms and the open sea, as a zoological haunt, stops with the light. It is hardly necessary to say that the pelagic plants are more abundant near the surface but at very low a certain depth the population consists almost exclusively of animals. Not a few of the animals sink and rise in the water periodically. There are some that come near the surface by day and others that come near the surface by night. Of great interest is the habit of the extremely delicate satenophores, or sea gooseberries, which the splash of a wave would tear into shreds. Whenever there is any hint of a storm, they sink beyond its reach and the ocean's surface must have remained flat as a mirror for many hours before they can be lured upwards from the calm of their deep retreat. The Floating Sea Meadows To understand the vital economy of the open sea we must recognize the incalculable abundance of minute unicellular plants for they form the fundamental food supply. Along with these must also be included numerous microscopic animals which have got possession of chlorophyll or have entered into internal partnership with unicellular algae, symbiosis. These green or greenish plants and animals are the producers using the energy of the sunlight to help them in building up carbon compounds out of air, water, and salts. The animals which feed on the producers or on other animals are the consumers. Between the two come those open sea bacteria that convert nitrogenous material, e.g. from dead plants or animals that other bacteria have rotted, into forms, e.g. nitrates, which plants can reutilize. The importance of these middlemen is great in keeping the circulation of matter a-going. The Floating Sea Meadows, as Sir John Murray called them, are always receiving contributions from in-shore waters where the conditions are favorable for the prolific multiplication of unicellular algae and there is also a certain amount of non-living sea dust always being swept out from the seaweed and seagrass area. Swimmers and Drifters The animals of the open sea are conveniently divided into the active swimmers, necton, and the more passive drifters, plankton. The swimmers include whales great and small, such birds as the storm petrol, the fish eating turtles and sea snakes, such fishes as mackerel and herring, the winged snails or sea butterflies on which whale bone whales largely feed, some of the active cuttles or squids, various open sea prawns and their relatives, some worms like the transparent arrow worm and such active protozoa as noctiluca, whose luminescence makes the waves sparkle in the short summer darkness. Very striking as an instance of the insurgence of life are the sea skimmers, Halobatidae, wingless insects related to the water measures in the ditch. They are found hundreds of miles from land, skimming on the surface of the open sea and diving in stormy weather. They feed on floating dead animals. The drifters, or easy-going swimmers, for there is no hard and fast line, are represented, for instance, by the flinty-shelled radiolarians and certain of the chalk-forming animals, globigaranid foraminifera. By jellyfishes, swimming-bells, and Portuguese men of war, by the comb-bearers, or satinophores, by legions of minute crustaceans, by strange animals called salps related to the sedentary sea squirts, and by some sluggish fishes like globefishes which often float idly on the surface. Open sea animals tend to be delicately built with a specific gravity near that of the sea water, with adaptations such as projecting filaments which help flotation, and with capacities of rising and sinking according to the surrounding conditions. Many of them are luminescent, and many of them are very inconspicuous in the water, owing to their transparency or their bluish color. In both cases, the significance is obscure. Hunger and Love Hunger is often very much in evidence in the open sea, especially in areas where the plankton is poor. For there is great diversity in this respect, most of the Mediterranean, for instance, having a scanty plankton as compared with the North Sea. In the South Pacific, west of Patagonia, there is said to be an immense sea desert where there is little plankton and therefore little in the way of fishes. The success of fisheries in the North, e.g. on the Atlantic cod banks, is due to the richness of the floating sea meadows and the abundance of the smaller constituents of the animal plankton. Hunger is plain enough when the baleen whale rushes through the water with open jaws, engulfing in the huge cavern of its mouth where the pendant whalebone plates form a huge sieve in calculable millions of small fry. But there is love as well as hunger in the open sea. The maternal care exhibited by the whale reaches a very high level and the delicate shell of the female paper nautilus or argonot in which the eggs and the young ones are sheltered may well be described as the most beautiful cradle in the world. Besides the permanent inhabitants of the open sea there are the larval stages of many shore animals which are there only for a short time. For there is an interesting give and take between the shore haunt and the open sea. From the shore come nutritive contributions and minute organisms which multiply quickly in the open waters. But not less important is the fact that the open waters afford a safe cradle or nursery for many a delicate larvae, e.g. of crab and starfish, acorn shell and sea urchin which could not survive for a day in the rough and tumble conditions of the shore and the shallow water. After undergoing radical changes and gaining strength the young creatures return to the shore in various ways. 3. The Deep Sea Very different from all the other haunts are the depths of the sea including the floor of the abysses and the zones of water near the bottom. This haunt, forever unseen, occupies more than a third of the earth's surface and it is thickly peopled. It came into emphatic notice in connection with the mending of telegraph cables but the results of the Challenger Expedition 1873 to 1876 gave the first impressive picture of what was practically a new world. 4. Physical Conditions The average depth of the ocean is about two and a half miles therefore since many parts are relatively shallow there must be enormous depths. A few of these, technically called deeps are about six miles deep in which Mount Everest would be engulfed. There is enormous pressure in such depths even at 2500 fathoms it is two and a half tons on the square inch. The temperature is on and off the freezing point of fresh water due to the continual sinking down of cold water from the poles especially from the south. Apart from the fitful gleams of luminescent animals there is utter darkness in the deep waters. The rays of sunlight are practically extinguished at 250 fathoms though very sensitive bromagellatin plates exposed at 500 fathoms have shown faint indications even at that depth. It is a world of absolute calm and silence and there is no scenery on the floor. A deep, cold, dark, silent, monotonous world biological conditions. While some parts of the floor of the abysses are more thickly peopled than others there is no depth limit to the distribution of life. Wherever the long arm of the dredge has reached animals have been found e.g. protozoa, sponges, corals, worms, starfishes sea urchins, sea lilies, crustaceans lamp shells, mollusks acidians, and fishes a very representative fauna. In the absence of light there can be no chlorophyll possessing plants and as the animals cannot all be eating one another there must be an extraneous source of food supply. This is found in the sinking down of minute organisms which are killed on the surface by changes of temperature and other causes. What is left of them before or after being swallowed and of sea dust and mineral particles of various kinds forms the diversified ooze of the sea floor a soft muddy precipitate which is said to have in places the consistence of butter in summer weather. There seems to be no bacteria in the abysses so there can be no rotting. Everything that sinks down even the huge carcass of a whale must be nibbled away by hungry animals and digested or else in the case of most bones slowly dissolved away. Of the whale there are left only the ear bones of the shark his teeth adaptations to deep sea life. In adaptation to the great pressure the bodies of deep sea animals are usually very permeable so that the water gets through and through them as in the case of Venus's flower basket a flinty sponge which a child's finger would shiver. But when the pressure inside is the same as that outside nothing happens. In adaptation to the treacherous ooze so apt to smother many of the active deep sea animals have very long stilt-like legs and many of the sedentary types are lifted into safety on the end of long stalks which have their bases embedded in the mud. In adaptation to the darkness in which there is only luminescence that eyes could see there is a great development of tactility. The interesting problem of luminescence will be discussed elsewhere. As to the origin of the deep sea fauna there seems no doubt that it has arisen by many contributions from the various shore haunts. Following the down-drifting food many shore animals have in the course of many generations reached the world of eternal night and winter and become adapted to its strange conditions. For the animals of the deep sea are as fit, beautiful and vigorous as those elsewhere. There are no slums in nature. Four. The fresh waters. Of the whole earth's surface the fresh waters form a very small fraction about a hundredth, but they make up for their smallness by their variety. We think of deep lake and shallow pond of the great river and the pearling brook of lagoon and swamp and more besides. There is a striking resemblance in the animal population of widely separated freshwater basins. And this is partly because birds carry many small creatures on their muddy feet from one watershed to another. Partly because some of the freshwater animals are descended from types which make their way from the sea shore through estuaries and marshes. And only certain kinds of constitution could survive the migration. And partly because some lakes are landlocked dwindling relics of ancient seas. And similar forms again would survive the change. A typical assemblage of freshwater animals would include many protozoa like amoebae and the bell and imalcules. A representative of one family of sponges, spongilidae. The common hydra. Many unsegmented worms notably planarians and nematodes. Many analytes related to the earthworms. Many crustaceans, insects and mites. Many bivalves and snails. Various fishes, a newt or two. Perhaps a little mud turtle or in warm countries a huge crocodilian. Various interesting birds like the water oozle or dipper and mammals like the water vole and the water shrew. Freshwater animals have to face certain difficulties, the greatest of which are drought, frost and being washed away in times of flood. There is no more interesting study in the world than an inquiry into the adaptations by which freshwater animals overcome the difficulties of the situation. We cannot give more than a few illustrations. One, drought is circumvented by the capacity that many freshwater animals have of lying low and saying nothing. Thus the African mudfish may spend half the year encased in the mud and many minute crustaceans can survive being dried up for years. Two, escape from the danger of being frozen hard in the pool is largely due to the almost unique property of water that it expands and approaches the freezing point. Thus the colder water rises to the surface and forms or adds to the protecting blanket of ice. The warmer water remains unfrozen at the bottom and the animals live on. Three, the risk of being washed away e.g. to the sea is lessened by all sorts of gripping, grappling and anchoring structures and by shortening the juvenile stages when the risks are greatest. Five, the dry land. Over and over again in the history of animal life there have been attempts to get out of the water onto terra firma and many of these have been successful notably those made one by worms two by air-breathing arthropods and three by amphibians. In thinking of the conquest of the dry land by animals we must recognize the indispensable rule of plants in preparing the way. The dry ground would have proved too inhospitable had not terrestrial plants begun to establish themselves affording food, shelter and humidity. There had to be plants before there could be earthworms which feed on decaying leaves and the like but how soon was the debt repaid when the earthworms began their worldwide task of forming vegetable mold opening up the earth with their burrows circulating the soil by means of their castings and bruising the particles in their gizzard certainly the most important mill in the world. Another important idea is that littoral haunts both on the seashore and in the fresh waters afforded the necessary apprenticeship and transitional experience for the more strenuous life on dry land. Much that was perfected on land had its beginnings on the shore. Let us inquire however what the passage from water to dry land actually implied. This has been briefly discussed in a previous article on evolution but the subject is one of great interest and importance. Difficulties and results of the transition from water to land. Leaving the water for dry land implied a loss in freedom of movement for the terrestrial animal is primarily restricted to the surface of the earth. Thus it became essential that movements should be very rapid and very precise needs with which we may associate the acquisition of fine, cross-striped quickly contracting muscles and also in time their multiplication into very numerous separate engines. We exercise 54 muscles in the half-second that elapses between raising the heel of our foot in walking and planting it firmly on the ground again. Moreover the need for rapid precisely controlled movements implied an improved nervous system for the brain was a movement controlling organ for ages before it did much in the way of thinking. The transition to terra firma also involved a greater compactness of body so that there should not be too great friction on the surface. An animal like the jellyfish is unthinkable on land and the elongated bodies of some land animals like centipedes and snakes are specially adapted so that they do not sprawl. They are exceptions that prove the rule. Getting on to dry land meant entering a kingdom where the differences between day and night between summer and winter are more felt than in the sea. This made it advantageous to have protections against evaporation and loss of heat and other such dangers. Hence a variety of ways in which the surface of the body acquired a thickened skin or a dead cuticle or a shell or a growth of hair and so forth. In many cases there is an increase of the protection before the winter sets in, e.g. by growing thicker fur or by accumulating a layer of fat below the skin. But the thickening or protection of the skin involved a partial or total loss of the skin as a respiratory surface. There is more oxygen available on dry land than in the water, but it is not so readily captured. Thus we see the importance of moist internal surfaces for capturing the oxygen which has been drawn into the interior of the body into some sort of lung. A unique solution was offered by tracheate arthropods such as parapatus, centipedes, millipedes and insects. Where the air is carried to every hole and corner of the body by a ramifying system of air tubes or trachea. In most animals the blood goes to the air. In insects the air goes to the blood. In the robber crab which has migrated from the shore inland the dry air is absorbed by vascular tufts growing under the shelter of the gill cover. The problem of disposing of eggs or young ones is obviously much more difficult on land than in the water. For the water offers an immediate cradle whereas on the dry land there were many dangers e.g. of drought, extremes of temperature and hungry sharp-eyed enemies which had to be circumvented. So we find all manner of ways in which land animals hide their eggs or their young ones in holes and nests on herbs and on trees. Some carry their young ones about after they are born like the Suriname Toad and the Kangaroo while others have prolonged the period of anti-natal life during which the young ones develop in safety within their mother and in very intimate partnership with her in the case of the placental animals. It is very interesting to find that the pioneer animal called parapatus which bridges the gap between worms and insects carries its young for almost a year before birth. Enough has been said to show that the successive conquests of the dry land had great evolutionary results. It is hardly too much to say that the invasion which the amphibians led was the beginning of better brains, more controlled activities and higher expressions of family life. 6. The Air There are no animals thoroughly aerial but many insects spend much of their adult life in the free air and the swift hardly pauses in its flight from dawn to dusk of the long summer day alighting only for brief moments at the nest to deliver insects to the young. All the active life of bats certainly deserves to be called aerial. The air was the last haunt of life to be conquered and it is interesting to inquire what the conquest implied. 1. It meant ascending the radical difficulty of terrestrial life which confines the creatures of the dry land to moving on one plane, the surface of the earth. But the power of flight brought its possessors back to the universal freedom of movement which water animals enjoy. When we watch a sparrow rise into the air just as the cat has completed her stealthy stalking we see that flight implies an enormous increase of safety. 2. The power of flight also opened up new possibilities of following the prey of exploring new territories of prospecting for water. 3. Of great importance too was the practicability of placing the eggs and the young perhaps in a nest in some place inaccessible to most enemies. When one thinks of it the rook's nests swaying on the treetops expresses the climax of a brilliant experiment. 4. The crowning advantage was the possibility of migrating, of conquering time by circumventing the arid summer and the severe winter and of conquering space by passing quickly from one country to another and sometimes almost girdling the globe. There are not many acquisitions that have meant more to their possessors than flight. It was a key opening the doors of a new freedom. The problem of flight, as has been said in a previous chapter, has been solved four times and the solution has been different in each case. The four solutions are those offered by insects, extinct pterodactyls, birds, and bats. Moreover, as has been pointed out, there have been numerous attempts of flying fishers, notably the flying fishes which take a great leap and hold their pectoral fins taut. The flying tree toad whose webbed fingers and toes form a parachute. The flying lizard, Dracovolans, which has its skin pushed out on five or six greatly elongated mobile ribs and various flying mammals, eg. flying phalanges with great swooping leaps from tree to tree. The wings of an insect are hollow, flattened sacs which grow out from the upper parts of the sides of the second and third rings of the region called the thorax. They are worked by powerful muscles and are supported like a fan by ribs of chitin which may be accompanied by air tubes, blood channels, and nerves. The insect's body is lightly built and very perfectly aerated and the principle of the insect's flight is the extremely rapid striking of the air by means of the lightly built elastic wings. Many an insect has over two hundred strokes of its wings in one second. Hence, in many cases, the familiar hum, comparable on a small scale to that produced by the rapidly revolving blades of an aeroplane's propeller. For a short distance a bee can outfly a pigeon but few insects can fly far and they are easily blown away or blown back by the wind. Dragonflies and bees may be cited as examples of insects that often fly for two or three miles but this is exceptional and the usual shortness of insect flight is an important fact for man since it limits the range of insects like houseflies and mosquitoes and vehicles of typhoid fever and malaria respectively. The most primitive insects spring tails and bristle tails show no trace of wings while fleas and lice have become secondarily wingless. It is interesting to notice that some insects only fly once in their lifetime namely in connection with mating. The evolution of the insect's wing remains quite obscure and probable that insects could run, leap and parachute before they could actually fly. The extinct flying dragons or pterodactyls had their golden age in the Cretaceous era after which they disappeared leaving no descendants. A fold of skin was spread out from the sides of the body by the enormously elongated outermost finger usually regarded as corresponding to our little finger. And thence to the tail. It is unlikely that the pterodactyls could fly far, for they have at most a weak keel on their breastbone. On the other hand some of them show a marked fusion of dorsal vertebrae which, as in flying birds must have served as a firm fulcrum for the stroke of the wings. The quaint creatures varied from the size of a sparrow up to a magnificent spread of fifteen to twenty feet tip to tip of the wings. They were the largest of all flying creatures. The bird's solution to the problem of flight which will be discussed separately is centered in the feather which forms a coherent vein for striking the air. In pterodactyl and bat the wing is a web wing or patagium and a small web is to be seen on the front side of the bird's wing. But the bird's patagium and the bird's wing is on an evolutionary tack of its own. A forelimb transformed for bearing the feathers of flight. Feathers are in a general way comparable to the scales of reptiles but only in a general way and no transition stage is known between the two. Birds evolved from a bipedal dinosaur stock as has been noticed already and it is highly probable that they began their ascent by taking running leaps on the ground flapping their scaly forelimbs and balancing themselves in kangaroo-like fashion with an extended tail. A second chapter was probably an arboreal apprenticeship during which they made a fine art of parachuting, a persistence of which is to be seen in the pigeon gliding from the dove-caught to the ground. It is in birds that the mastery of the air reaches its climax and the vulture is surely the most remarkable locomotor triumph that has ever been achieved. Without any apparent stroke of the wings the bird sails for half an hour at a time with the wind and against the wind around the ship and in majestic spirals in the sky probably taking advantage of currents of air of different velocities and continually changing the energy of position into energy of motion as it sinks and energy of motion into energy of position as it rises. It is interesting to know that some dragonflies are also able to sail. The web-wing of bats involves much more than the forearm. The double fold of skin begins on the side of the neck, passes along the front of the arm, skips the thumb, and is continued over the elongated palm bones and fingers to the sides of the body again and to the hind legs and to the tail, if there is a tail. It is interesting to find that the bones of the bat's skeleton tend to be lightly built as in birds that the breast bone has likewise a keel for the better insertion of the pectoral muscles and that there is a solidifying on the vertebrae of the back affording, as in birds, a firm basis for the wing action. Such similar adaptations to similar needs occurring in animals not nearly related to one another are called convergences and form a very interesting study. In addition to adaptations which the bat shares with the flying bird it has many of its own. There are so many nerve endings on the wing and often also on special skin leaves about the ears and nose that the bat flying in the dusk does not knock against branches or other obstacles. Some say that it is helped by the echoes of its high-pitched voice but there is no doubt as to its exquisite tactility. That it usually produces only a single young one at a time is a clear adaptation to flight and similarly the sharp mountaintop-like cusps on the back teeth are adapted in insectivorous bats for crunching insects. Whether we think of the amphant flight of birds reaching a climax in migration or of the marvel that a creature of the earth, as a mammal essentially is, should evolve such a mastery of the air as we see in bats or even of the repeated but splendid failures which parachuting animals illustrate we gain an impression of the insurgence of living creatures in their characteristic endeavor after fuller well-being. We have said enough to show how well-adapted many animals are to meet the particular difficulties of the haunt which they tenet. But difficulties and limitations are ever arising afresh and so one fitness follows on another. It is natural, therefore, to pass to the frequent occurrence of protective resemblance, camouflage and mimicry the subject of the next article. End of Section 6 Read by Kara Schellenberg www.kray.org On June 28, 2008 in San Diego, California Section 7 of the Outline of Science Volume 1 This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer please visit LibriVox.org Recording by James Christopher The Outline of Science Volume 1 Section 7 Part 4 The Struggle for Existence Animal and Bird Mimicry in Disguise 1 For every animal one discovers when observing carefully there must be ten unseen. This is partially because many animals burrow in the ground or get in underneath things and into dark corners. Being what is called cryptozoic or elusive. But it is partly because many animals put on disguise or have in some way acquired a garment of invisibility. This is very common among animals and it occurs in many forms and degrees. The reason why it is so common is because the struggle for existence is often very keen. And the reasons why the struggle for existence is keen are four. First, there is a tendency to overpopulation in many animals, especially those of low degree. Second, there is a fact that the scheme of nature involves nutritive change or successive incarnations. One animal depending upon another for food and all in the long run on plants. Thirdly, every vigorous animal is a bit of a hustler. Given to insurgence and sticking out his elbows. There is a fourth great reason for the struggle for existence. Namely, the frequent changefulness of a physical environment which forces animals to answer back or die. But the first three reasons have most to do with the very common assumption of some sort of disguise. Even when an animal is in no sense a weakling it may be very advantageous for it to be inconspicuous when it is resting or when it is taking care of its young. Our problem is the evolution of elusiveness. So far at least as that depends on likeness to surroundings. On protective resemblance to other objects and in its highest reaches on true mimicry. Color permanently like that of surroundings. Many animals living on sandy places have a light brown color as is seen in some lizards and snakes. The green lizard is like the grass and the green tree snake is inconspicuous among the branches. The spotted leopard is suited to the interrupted light of the forest and it is sometimes hard to tell where the jungle ends and the striped tiger begins. There is no better case than the hare or the partridge sitting a few yards off in the plowed field. Even a donkey grazing in the dusk is much more readily heard than seen. The experiment has been made of tethering the green variety of praying mantas on green herbage fastening them with silk threads. They escape the notice of birds. The same is true when the brown variety is tethered on withered herbage. But if the green ones are put on brown plants or the brown ones on green plants, the birds pick them off. Similarly, out of 300 chickens in a field, 240 whiter black and therefore conspicuous, 60 spotted and inconspicuous, 24 were soon picked off by crows, but only one of these was spotted. This was not the proportion that there should have been if the mortality had been fortuitous. There is no doubt that it often pays an animal to be like its habitual surroundings, like a little piece of scenery if the animal is not moving. It is safe to say that in process of time, wide departures from the safest coloration will be wiped out in the course of nature's ceaseless sifting. But we must not be credulous, and there are three cautions to be born in mind. One, an animal may be very like its surroundings without there being any protection implied. The error worms in the sea are as clear as glass, and so are many open sea animals. But this is because their tissues are so watery, with a specific gravity near that of salt water, and the invisibility does not save them, always or often, from being swallowed by larger animals that gather the harvest of the sea. Two, among the cleverer animals, it looks as if the creature sometimes sought out a spot where it was most inconspicuous. A spider may place itself in the middle of a little patch of lichen, where its self-effacement is complete. Perhaps it is more comfortable as well as safer to rest in surroundings the general color of which is like that of the animal's body. Three, the fishes that live among the coral reefs are startling in their brilliant coloration, and there are many different patterns. To explain this, it has been suggested that these fishes are so safe among the mazy passages and endless nooks of the reef, that they can well afford to wear any color that suits their constitution. In some cases, this may be true. But naturalists who have put on a diving suit and walked about among the coral have told us that each kind of fish is particularly suited to some particular place, and that some are suited for midday work and others for evening work. Sometimes there is a sort of box and cocks arrangement by which two different fishes utilize the same corner at different times. Two, gradual change of color. The common shore crab shows many different colors and modelings, especially when it is young. It may be green or gray, red or brown and so forth, and it is often an admirable adjustment to the color of the rock pool where it is used. Experiments which require extension have shown that when the crab has molted, which it has to do very often when it is young, the color of the new shell tends to harmonize with the general color of the rocks and seaweed. How this is brought about, we do not know. The color does not seem to change till the next molt, and not then unless there is some reason for it. A full-grown shore crab is well able to look after itself, and it is of interest to notice therefore that the variety of coloration is mainly among the small individuals who have, of course, a much less secure position. It is possible, moreover, that the resemblance to the surroundings admits of more successful hunting, enabling the small crab to take its victim unawares. Professor Poulton's experiments with the caterpillars of the small tortoise shell butterfly showed that in black surroundings the pupae tend to be darker. In white surroundings later. In gilded boxes golden, and the same is true in other cases. It appears that the surrounding color affects the caterpillars through the skin during a sensitive period. The twenty hours immediately proceeding the last twelve hours of the larval state. The result will tend to make the quiescent pupae less conspicuous during the critical time of metamorphosis. The physiology of this sympathetic coloring remains obscure. Seasonal change of coloring. The ptarmigan molts three times in a year. Its summer plumage is rather gross like above, with a good deal of roughest brown. That becomes much more gray in autumn. Almost all the feathers of the winter plumage are white. That is to say, they develop without any pigment, and with numerous gas bubbles in their cells. Now there can be no doubt that this white winter plumage makes the ptarmigan very inconspicuous amidst the snow. Sometimes one comes within a few feet of the crouching bird without seeing it, and this garment of invisibility may save it from the hungry eyes of golden eagles. Similarly, the brown stote becomes the white ermine, mainly by the growth of a new suit of white fur, and the same is true of the mountain hair. The ermine is all white except the black tip of its tail. The mountain hair in its winter dress is all white save the black tips of its ears. In some cases, especially in the mountain hair, it seems that individual hairs may turn white by loss of pigment, as may occur in man. According to Mechnikov, the wandering ameboid cells of the body, called phagocytes, may creep up into the hairs and come back again with microscopic burdens of pigment. The place of the pigment is taken by gas bubbles, and that is what causes the whiteness. In no animals is there any white pigment. The white color is like that of snow or foam. It is due to the complete reflection of the light from enumerable minute surfaces of crystals or bubbles. The mountain hair may escape the fox the more readily because its whiteness makes it so inconspicuous against a background of snow. And yet, at other times, we have seen the creature standing out like a target on the dark moorland. So it cuts both ways. The ermine has almost no enemies except the gamekeeper, but its winter whiteness may help it to sneak upon its victims, such as grouse or rabbit, when there is snow upon the ground. In both cases, however, the probability is that the constitutional rhythm which leads to white hair in winter has been fostered and fixed for a reason quite apart from protection. The fact is that for a warm-blooded creature, whether bird or mammal, this is logically best dressed as a white one, for there is less radiation of the precious animal heat from white plumage or white pelage than from any other color. The quality of warm-bloodedness is a prerogative of birds and mammals. And it means that the body keeps in almost constant temperature day and night, year in and year out. This is affected by the automatic internal adjustment which regulate the supply of heat chiefly from the muscles to the loss of heat chiefly through the skin and from the lungs. The importance of this internal heat is that it facilitates the smooth continuance of the chemical processes on which life depends. If the temperature falls, as in hibernating mammals, whose warm-bloodedness is imperfect, the rate of the vital process is slowed down, sometimes dangerously. Thus we see how the white coat helps the life of the creature. 3. Rapid Color Change Bony flatfishes, like place and soul, have a remarkable power of adjusting to the surrounding gravel and sand, so that it is difficult to find them even when we know that they are there. It must be admitted that they are also very quick to get a sprinkling of sand over their upturned side, so that only the eyes are left showing. But there is no doubt, as to the exactness with which they often adjust themselves to be just like a little piece of the substrate among which they lie. They will do this within limits in experimental conditions when they are placed on a quite artificial floor. These fishes are very palatable and are much sought after by such enemies as cormorants and otters. It is highly probable that their power of self-effacement often saves their life. And it may be affected within a few minutes, in some cases, within a minute. In these self-effacing flatfishes we know with some precision what happens. The adjustment of color and pattern is due to changes in the size, shape and position of mobile pigment cells, chromatophores, and the skin. But what makes the pigment cells change? The fact that a blind flatfish does not change its color gives us the first part of the answer. The color and the pattern of the surroundings must affect the eye. The message travels by the optic nerve to the brain. From the brain, instead of passing down the spinal cord, the message travels down the chain of sympathetic ganglia. From these it passes along the nerves which comes out of the spinal cord and control the skin. Thus the message reaches the color cells in the skin, and before you have carefully read these lines, the flatfish has slipped on its gauges ring and becomes invisible. The same power of rapid color change is seen in cuttlefish, where it is often an expression of nervous excitement, though it sometimes helps to conceal. It occurs with much subtlety in the asop prawn, Hippolyte, which may be brown on a brown seaweed, green on sea lettuce or sea grass, red on red seaweed, and so on through an extensive repertoire. According to the nature of the background, Professor Gimbel writes, so is the mixture of the pigments compounded so as to form a close reproduction both of its color and its pattern. A sweep of the shrimp net detaches a battalion of these sleeping prawns, and if we turn the motley into a dish and give a choice of seaweed, each variety after its kind will select the one with which it agrees in color and vanish. When both young and when full grown, the asop prawn takes on the color with immediate surroundings. The red of whatever color changes to a transparent azure blue. Its stolidity gives place to a nervous restlessness. At the least tremor it leaps violently and often swims actively from one food plant to another. This blue fit lasts until daybreak and is then succeeded by the prawn's diurnal tint. Thus, Professor Gimbel continues, the color of an animal may express a nervous rhythm. The case of chameleons. Each rapid color change occurs as among lizards, and the finest exhibition of it is among the chameleons. These quaint creatures are characteristic of Africa, but they also occur in Andalusia, Arabia, Ceylon, and southern India. They are adapted for life on trees, where they hunt insects with great deliberateness and success. The protrusable tongue, ending in a sticky club, can be shot out for about 7 inches in the common chameleon. Their hands and feet are split so that they grip the branches firmly and the prehensile tail rivals the monkeys. When they wish, they can make themselves very slim, contracting the body from side to side so that they are not very readily seen. In other circumstances, however, they do not practice self-effacement but the very reverse. They inflate their bodies, having not only large lungs, but air sacs in connection with them. The throat bulges, the body sways from side to side, and the creature puts its sentiments in a hiss. The power of color change is very remarkable and depends partly on the contraction and expansion of the color cells, chromatophores, in the underskin, or dermis, and partially on close-packed, refractive granules and crystals of a waste product called guanen. The repertoire of possible colors in the common chameleon is greater than in any other animal except the ace-up prawn. There is a legend of a chameleon which was brown in a brown box, green in a green box, and blue in a black box, and dyed when put into one line with tartan. And there is no doubt that one in the same animal has a wide range of colors. The so-called chameleon, a nullis of North America, is so sensitive that a passing cloud makes its change its emerald hue. There is no doubt that a chameleon may make itself more inconspicuous by changing its color, being affected by the play of light on its eyes. A bright green hue is often seen on those that are sitting among strongly green leaves, but the color also changes with the time of day and with the animal's moods. A sudden irritation may bring about a rapid change. In other cases, a transformation comes about very gradually. When the color change expresses a chameleon's feelings, it might be compared to blushing. But that is due to an expansion of the arteries of the face, allowing more blood to get into the capillaries of the underskin. The case of the chameleon is peculiarly interesting because the animal has two kinds of chameleons. Self-effacement on the one hand and bluffing on the other. There can be little doubt that the power of color change sometimes justifies a self by driving off intruders. Dr. Cyril Crosslin observed that a chameleon attacked by a fox terrier turned round and opened its great pink mouth in the face of the advancing dog, at the same time rapidly changing color, becoming almost black. This ruse succeeded every time, the dog turning off at once. The leafy surroundings of startling effect would be much greater. A sun throwing off of the mantle of invisibility and the exposure of a conspicuous black body with a large red mouth. Four. Likeness to other things. Dr. H. O. Forbes tells of a flat spider which presents a striking resemblance to a bird dropping on a leaf. Years after he first found it, he was watching in a forest in the far east when his eye fell on a leaf before him which had been blotched by a bird. It was vitally why he had not seen for so long another specimen of the bird dropping spider or Nithos Gadadi's Deceptians and drew the leaf towards him. Instantaneously he got a characteristic sharp nip. It was a spider after all. Here the color resemblance was enhanced by a form resemblance. But why should it profit a spider to be like a bird dropping? Perhaps because it thereby escapes attention but there is another possibility. It seems that some butterflies like to our blues are often attracted to excrementious material and the spider Dr. Forbes observed had actually caught its victim. This is borne out by a recent observation by Dr. D. G. H. Carpenter who found a Uganda bug closely resembling a bird dropping on sand. The bug actually settled down on a bird dropping on sand and caught a blue butterfly which came to feed there. Some of the walking stick insects belonging to the order of crickets and grasshoppers, or Thoptera, belong gated and narrow like a thin dry branch and they have a way of sticking out their limbs at abrupt and diverse angles which makes a resemblance to twigs very close indeed. Some of these quaint insects rest through the day and have the remarkable habit of putting themselves into a sort of cataleptic state. Many creatures turn stiff when they get a shock or pass suddenly into new surroundings like some of the sandhoppers when we lay them on the palm of our hand but these twig insects put themselves into this strange state. The body is rocked from side to side for a short time and then it stiffens. An advantage may be that even if they were surprised by a bird or a lizard they will not be able to betray themselves even by a trimmer. Disguise is perfected by a remarkable habit a habit which leads us to think of a whole series of different ways of lying low and saying nothing which are often of life preserving value. The top end of the series is seen when a fox plays possum. The leaf butterfly, Kalama, conspicuously discoloured on its upper surface is like a withered leaf when it settles down and shows the underside of its wings. Here again, there is a precise form resemblance for the nourritures on the wings are like the mid-rib and side veins on a leaf and the touch of perfection is given in the presence of whitish spots which look exactly like the discolorations produced by lichens on leaves. An old entomologist, Mr. Jennifer Weir confessed that he repeatedly pruned off a caterpillar on a bush a mistake for a superfluous twig. The caterpillars fasten themselves by their posterior claspers and by an invisible thread of silk from their mouth and project from the branch at a twig-like angle. An insect may be the very image of a sharp prickle or a piece of soft moss. A spider may look precisely like a tiny knob on a branch or a fragment of lichen. One of the seahorses, phylopterics, has fron-like tassels on various parts of its body so that it looks extraordinarily like the seaweed among which it lives. In a few cases, e.g. spiders, it has been shown that animals with a special protective resemblance to something else seek out a position where this resemblance tells, and there is urgent need for observations very on the selection of environment. 5. Mimicry in the true sense It sometimes happens that in one in the same place there are two groups of animals not very nearly related which are doubles of one another. Investigation shows that the members of one group, always in the majority, are in some way specially protected, e.g. by being unpalpable. They are the mimicked. The members of the other group, always in the minority, have not got the special protectant possessed by the others. They are the mimickers, though the resemblance is not, of course, associated with any conscious imitation. The theory is that the mimickers live on the reputation of the mimicked. If the mimicked are left alone by the birds because they have a reputation for unpalpability or because they are able to sting, the mimickers survive, although they are palpable and stingless. They succeed not through any virtue of their own, but because of their resemblance to the mimicked, for whom they are mistaken. There are many cases of mimetic resemblance so striking and so subtle that it seems impossible to doubt that the thing works. There are other cases which are rather far-fetched and may be somewhat of the nature of coincidences. Thus, although Mr. Bates tells us that he repeatedly shot hummingbird moss in mistake for hummingbirds, we cannot think that this is a good illustration of mimicry. What is needed for many cases is what is forthcoming for some, namely experimental evidence, e.g. that the unpalpability butterflies are left in relative peace while similar palatable butterflies are persecuted. It is also necessary to show that the mimickers do actually consort with the mimicked. Some beetles and moths are curiously wasp-like, which may be a great advantage. The common drone fly is superficially like a small bee. Some harmless snakes are very like poisonous species. And Mr. Wallace maintained that the powerful friar birds of the east are mimicked by the weak and timid orioles. When the model is unpalpable or repulsive or dangerous and the mimic the reverse, the mimicry is called Batesian after Mr. Bates. But there is another kind of mimicry called Malarian after Fritz Mahler where the mimic is also unpalpable. The theory in this case is that the mimicry serves as a mutual assurance. The members of the ring getting on better by consistently presenting the same appearance which has come to mean to possible enemies a signal, no lie me tangray, leave me alone. There is nothing out of the question in this theory, but it requires to be taken in a critical spirit. It leads us to think of warning colors which are the very opposite of the disguises which we are now studying. Some creatures like skunks, magpies, coral snakes, cobras, brightly colored orioles are exclusive. And the theory of Alfred Russell Wallace was that the flaunting conspicuousness serves as a useful advertisement impressing itself on the memories of inexperienced enemies who soon learn to leave the creatures with warning colors alone. In any case it is plain that an animal which is as safe as a wasp or a coral snake can afford to wear any suit of clothes it likes. Masking The episode in Scottish history called the Walking Wood of Burnham has had its counterpart in many countries. But it is also enacted on the seashore. There are many kinds of crabs that put on disguise with what looks like deliberateness. The sand crab takes a piece of seaweed, nibbles at the end of it, and then rubs it on the back of the carapace or on the leg so that it fixes to the bristles. As the seaweed continues to live the crab soon has a little guarded on its back which masks the crab's real nature. It is most effective camouflaging, but if the crab continues to grow it has to molt. And that means losing the disguise. It is then necessary to make a new one. The crab must have on the shore something corresponding to a reputation. That is to say, other animals are clearly or dimly aware that the crab is a voracious and combative creature. How useful to the crab then to have its appearance cloaked by a growth of innocent seaweed, or sponge, or zoo fight. It will enable the creature to sneak up upon its victims or to escape the attention of its own enemies. If a narrow-beaked crab is cleaned artificially it will proceed to clothe itself again. The habit has become instinctive. And it must be admitted that while a particular crab prefers a particular kind of seaweed for its dress it will cover itself with unsuitable and even conspicuous material such as pieces of colored cloth if nothing better is available. The disguise differs greatly for one crab is masked by a brightly colored and unpalpable sponge densely packed on the surface. Another cuts off the tunic of a sea squirt and throws it over its shoulders. Another trundles about a bivalve shell. The facts recall the familiar case of the hermit crab which protects its soft tail by tucking it into the empty shell of a periwinkle or a welk or some other sea snail. And that case leads on to the elaboration known as commensalism. Where the hermit crab fixes sea anemones on the back of its borrowed house. The advantage here is beyond that of masking which is a useful quality in a partner. That this second advantage may become the main one is evident in several cases where the sea anemone is born just like a weapon on each of the crustaceans great claws. Moreover, as a term commensalism, eating at the same table, suggest the partnership is mutually beneficial. For the sea anemone is carried about by the hermit crab and a doubtless gets its share of crumbs from its partner's frequent meals. There is a very interesting sidelight on the mutual benefit in the case of the dislodged sea anemone which sculpt for a while and then waited in the state of preparedness until a hermit crab passed it and touched it. Whereupon the sea anemone gripped and slowly worked itself up to the back of the shell. Six. Other kinds of elusiveness. There are various kinds of disguise which are not readily classified. A troop of cuttlefish swimming in the sea is a beautiful sight. They keep time with one another in their movements and they show the same change of color almost at the same moment. They are suddenly attacked however by a small shark and then comes a simultaneous discharge of sepia from their ink bags. There are clouds of ink in the clear water. Four, as Professor Hickson puts it, the cuttlefish have thrown dust in the eyes of their enemies. One can see a newborn cuttlefish do this a minute after it escapes from the egg. Very beautiful is the way in which many birds like our common kayfinch disguise the outside of their nest with moss and lichens and other trifles felted together so that the cradle is as inconspicuous as possible. There seems to be a touch of art in fastening pieces of spider webs on the outside of a nest. How curious is the case of the tree sloth of South American forest that walks slowly down backwards along the undersides of the branches hanging on by its long curved fingers and toes. It is a nocturnal animal and therefore not in special danger, but when resting during the day it is almost invisible because its shaggy hair is so like certain lichens and other gross on the branches. But the protective resemblance is enhanced by the presence of a green algae which actually lives on the surface of the sloth's hairs. An algae like the one that makes tree stems and gateposts green in damp weather. There is no commonerside in the early days of summer than the cuckoo spit on the grasses and herbage by the wayside. It is conspicuous and yet it is said to be left severely alone by almost all creatures. In some way it must be a disguise. It is a sort of soap made by the activity of small frog hoppers while they are still in the wingless larval stage before they begin to hop. The insect pierces with its sharp mouth parts the skin of the plant and sucks in sweet sap which by and by overflows over its body. It works its body up and down many times whipping in air which mixes with the sugary sap reminding one of how whipped egg is made. But along with the sugary sap in the air there is a little ferment from the food canal and a little wax from glands on the skin and the four things mixed together make a kind of soap which lasts through the heat of the day. There are many other modes of disguise besides those which we have been able to illustrate. Indeed the biggest fact is that there are so many for it brings us back to the idea that life is not an easy business. It is true as Walt Whitman says that animals do not sweat and whine about their condition. Perhaps it is true as he says that not one is unhappy over the whole earth. But there is another truth that this world is not a place for the unlit lamp in the ungurt loin and that when a creature has not armor or weapons or cleverness it must find some path of safety or go back. One of these paths of safety is disguise and we have illustrated its evolution. End of Section 7 Recording by James Christopher JxChristopher at yahoo.com Section 8 of the Outline of Science Volume 1 This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer please visit LibriVox.org The Outline of Science Volume 1 by J. Arthur Thompson Section 8 Part 5 The Ascent of Man No one thinks less of Sir Isaac Newton because he was born a very puny infant and no one should think less of the human race because it sprang from a stalk of arboreal mammals. There is no doubt as to man's apartness from the rest of creation when he is seen at his best, a little lower than the angels, crowned with glory and honor. What a piece of work, how noble in reason, how infinite in faculty, in form and moving, how express and admirable, in action, how like an angel, in apprehension, so like a god. Nevertheless, all the facts point to his affiliation to the stock to which monkeys and apes also belong. Not indeed that man is descended from any living ape or monkey, it is rather that he and they have sprung from a common ancestry, or branches of the same stem. This conclusion is so momentous that the reasons for accepting it must be carefully considered. They were expounded with masterly skill in Darwin's Descent of Man in 1871, a book which was but an expansion of a chapter in the Origin of Species, 1859. Anatomical Proof of Man's Relationship with a Simmy in Stock. The anatomical structure of man is closely similar to that of the anthropoid apes, the gorilla, the orang, the chimpanzee and the gibbon. Bone for bone, muscle for muscle, blood vessel for blood vessel, nerve for nerve, man and ape agree. As the conservative anatomist Sir Richard Owen said, there is between them an all-pervading similitude of structure. Differences of course there are, but they are not momentous except man's big brain which may be three times as heavy as that of a gorilla. The average human brain weighs about 48 ounces. The gorilla brain does not exceed 20 ounces at its best. The capacity of the human skull is never less than 55 cubic inches. In the orang and the chimpanzee the figures are 26 and 27 and a half respectively. We are not suggesting that the most distinctive features of man are such as can be measured and weighed, but it is important to notice that the main mental powers is physically far ahead of that of the highest of the anthropoid apes. Man alone is thoroughly erect after his infancy is passed. His head, weighted with the heavy brain, does not droop forward as the apes does. With his erect attitude there is perhaps to be associated his more highly developed vocal organs. Compared with an anthropoid ape, man has a bigger and more upright forehead, a less protrusive face region, smaller cheekbones and eyebrow ridges and more uniform teeth. He is almost unique in having a chin. Man plants the soul of his foot flat on the ground, his big toe is usually in a line with the other toes and he has a better heel than any monkey has. The change of the shape of the head is to be thought of in connection with the enlargement of the brain and also in connection with the natural reduction of the muzzle region when the hand was freed from being an organ of support and became suited for grasping food and conveying it to the mouth. Everyone is familiar in man's clothing with traces of the past persisting in the present though their use has long since disappeared. There are buttons on the back of the waist of the morning coat to which the tails of the coat used to be fastened up and there are buttons occasionally with button holes at the wrist which were once useful in turning up the sleeve. The same is true of man's body which is a veritable museum of relics. Some anatomists have made out a list of over a hundred of these vestigial structures and though this number is perhaps too high there is no doubt that the list is long. In the inner upper corner of the eye there is a minute tag but larger in some races than in others which is the last dwindling relic of the third eyelid used in cleaning the front of the eye which most mammals possess in a large and well developed form. It can be easily seen for instance in ox and rabbit. In man and in monkeys it has become a useless vestige and the dwindling must be associated with the fact that the upper eyelid is much more mobile in man and monkeys than in the other mammals. The vestigial third eyelid in man is enough of itself to prove his relationship with the mammals but it is only one example out of many. Some of these are discussed in the article dealing with the human body but we may mention the vestigial muscles going to the ear trumpet man's dwindling counterpart of the skin twitching muscle which we see a horse use when he jerks a fly of his wings and the short tail which in the 7 weeks old human embryo is actually longer than the leg. Without committing ourselves to a belief in the entire uselessness of the vermaform appendix which grows out as a blind alley at the junction of the small intestine with the large we are safe in saying that it is a dwindling structure the remains of a blind gut which must have been capacious and useful in ancestral forms. In some mammals like the rabbit the vestigial structure in the body and bears the vermaform appendix at its far end in man the appendix alone is left and it tells its tail it is interesting to notice that it is usually longer in the orang than in man and that it is very variable as dwindling structures tend to be one of the unpleasant expressions of this variability is the liability to go wrong hence appendicitis now these vestigial structures are as Darwin said like the unsounded that is, functionless letters in words such as the O in leopard the B in doubt the G in rain they are of no use but they tell us something of the history of the words so do man's vestigial structures reveal his pedigree they must have an historical or evolutionary significance no other interpretation is possible some men, oftener than women show on the interned margin of the ear trumpet or pinna a little conical projection of great interest it is the vestige of the tip of the pointed ear of lower mammals and it is well named Darwin's point it was he who described it as a surviving symbol of the stirring times and dangerous days of man's animal youth 2. Physiological proof of man's relationship with a simian stock the everyday functions of the human body are practically the same as those of the anthropoid ape and similar disorders are common to both monkeys may be infected with certain microbes to which man is peculiarly liable, such as the bacillus of tuberculosis Darwin showed that various human gestures and facial expressions have their counterparts in monkeys the sneering curl of the upper lip which tends to expose the canine tooth is a case in point though it may be seen in other mammals besides monkeys in dogs for instance which are at some considerable distance from the simian branch to which man's ancestors belonged when human blood is transfused into a dog or even a monkey it behaves in a hostile way to the other blood bringing about a destruction of the red blood corpuscles but when it is transfused into a chimpanzee there is an harmonious mingling of the two this is a very literal demonstration of man's blood relationship with the higher apes but there is a finer form of the same experiment when the blood fluid or serum of a rabbit which has had human blood injected into it when it is mingled with human blood it forms a cloudy precipitate it forms almost as marked a precipitate when it is mingled with the blood of an anthropoid ape but when it is mingled with the blood of an American monkey there is only a slight clouding after a considerable time and no actual precipitate when it is added to the blood of one of the distantly related half monkeys or lemurs there is no reaction or only a very weak one with the blood of mammals off the simian line altogether there is no reaction at all thus as a distinguished anthropologist Professor Schwebel has said we have in this not only a proof of the literal blood relationship between man and apes but the degree of relationship with the different main groups of apes can be determined beyond possibility of mistake we can imagine how this modern line of experiment would have delighted Darwin embryological proof of man's relationship with a simian stock in his individual development man does in some measure climb up his own genealogical tree stages in the development of the body during its nine months of antinatal life are closely similar to stages in the development of the anthropoid embryo babies born in times of famine or siege are sometimes as it were imperfectly finished and sometimes have what may be described as monkey-ish features and ways a visit to an institution for the care of children who show arrested, defective or disturbed development Darwin sadly impressed with the risk of slipping down the rungs of the steep ladder of evolution and even in adults the occurrence of serious nervous disturbance such as shell shock is sometimes marked by relapses to animal ways it is a familiar fact that a normal baby reveals the past in its surprising power of grip and the careful experiments of Dr. Louis Robinson showed that an infant three weeks old could support its own weight for over two minutes holding on to a horizontal bar in many cases no signs of distress is evinced and no cry uttered until the grass begins to give this persistent grass probably points back to the time when the baby had to cling to its arboreal mother the human tail is represented in the adult by a fusion of four or five vertebrae forming the coccyx at the end of the backbone and is normally concealed beneath the flesh but in the embryo the tail projects freely and is movable up to the six months of the antinatal sleep the body is covered all but the palms and soles with longish hair the lanugo which usually disappears before birth this is a stage in the normal development which is reasonably interpreted as a recapitulation of a stage in the racial evolution we draw this inference when we find that the unborn offspring of an almost hairless whale has an abundant representation of hairs we must draw a similar inference in the case of man it must be noticed that there are two serious errors in this statement often made that man and his development is at one time like a little fish at a later stage like a little reptile at a later stage like a little primitive mammal and eventually like a little monkey the first error here is that the comparison should be made with embryo fish, embryo reptile embryo mammal and so on it is in the making of the embryos that the great resemblance lies when the human embryo shows the laying down of the essential vertebrae characters such as brain and spinal cord then it is closely comparable to the embryo of a lower vertebrae at a similar stage when at a subsequent stage its heart for instance is about to become a four-chambered mammalian heart it is closely comparable to the heart of let us say a turtle which never becomes more than three-chambered the point is that in the making of the organs of the body say brain and kidneys the embryo of man pursues a path closely corresponding to the path by the embryos of other back-boned animals lower in the scale but at successive stages it parts company with these with the lowest first and so on in succession a human embryo is never like a little reptile but the developing organs pass through stages which very closely resemble the corresponding stages in lower types which are in a general way ancestral the second error is that every kind of animal, man included has from the first a certain individuality with peculiar characteristics which are all its own this is expressed by the somewhat difficult word specificity which just means that every species is itself and no other so in the development of the human embryo while there are close resemblances to the embryos of apes, monkeys, other mammals and even at earlier stages still to the embryos of reptile and fish, it has to be admitted that we are dealing from first to last with a human embryo with peculiarities of its own every human being begins his or her life as a single cell a fertilized egg cell a treasure house of all the ages for in this living microcosm only a small fraction one one twenty fifth of an inch in diameter there is condensed, who can imagine how all the natural inheritance of man all the legacy of his parentage of his ancestry of his long pre-human pedigree Darwin called the pinhead brain of the ant the most marvelous atom of matter in the world but the human ovum is more marvelous still it has more possibilities in it than any other thing yet without fertilization it will die the fertilized ovum divides and re-divides thus results a ball of cells and a sack of cells gradually division of labor becomes the rule there is a laying down of nervous system and food canal muscular system and skeleton and so proceeds what is learnedly called differentiation out of the apparently simple there emerges the obviously complex as Aristotle observed more than two thousand years ago in the developing egg of the hen there soon appears the beating heart there is nothing like this in the non-living world but to return to the developing human embryo there is formed from and above the embryonic food canal a skeletal rod which is called the notochord it thrills the imagination to learn by supporting axes that the lower orders of the backboneed race possess the curious thing is that it does not become the backbone which is certainly one of the essential features of the vertebrate race the notochord is the supporting axis of the pioneer backboneed animals namely the landslits and the round mouths cyclistomes such as the lamprey they have no backbone in the strict sense but they have this notochord it can easily be dissected out in the lamprey a long gristly rod it is surrounded by a sheath which becomes the backbone of most fishes and of all higher animals the interesting point is that although the notochord is only a vestige in the adults of these types it is never absent from the embryo it occurs even in man a short-lived relic of the primeval supporting axis of the body it comes and then it goes leaving only minute traces in the adult we cannot say that it is of any use but it serves as a stimulus to the development of its substitute the backbone it is only a piece of preliminary scaffolding but there is no more eloquent instance of the living hand of the past one other instance must suffice of what professor law calls the wonderful changes wrought in the dark of the antinatal period which recapitulate in rapid abbreviation the great evolutionary steps which were taken by man's ancestors during the long night of the geological past on the sides of the neck of the human embryo there are four pairs of slits the visceral clefs openings from the beginning of the food canals to the surface there is no doubt as to their significance they correspond to the gill slits of fishes and tadpoles yet in reptiles, birds and mammals they have no connection with breathing which is their function in fishes and amphibians indeed they are not of any use at all but that the first becomes the eustachian tube bringing the ear passage into connection with the back of the mouth and that the second and third have to do with the development of a curious organ called the thymus gland persistent nevertheless these gill slits are recalling even in man an aquatic ancestry of many millions of years ago when all these lines of evidence are considered they are seen to converge in the conclusion that man is derived from a simian stalk of mammals he is solitary with the rest of creation to quote the closing words of Darwin's descent of man we must however acknowledge as it seems to me that man with all his noble qualities with sympathy which feels for the most based with benevolence which extends not only to other men but to the humblest living creature with his god-like intellect which has penetrated into the movements and constitution of the solar system with all these exalted powers in his bodily frame the indelible stamp of his lowly origin we should be clear that this view does not say more than that man sprang from a stalk common to him and to the higher apes those who are repelled by the idea of man's derivation from a simian type should remember that the theory implies rather more than this namely that man is the outcome of a genealogy which has implied many millions of years of experimenting and sifting the groaning and interveiling of a whole creation speaking of man's mental qualities Sir Ray Lancaster says they justify the view that man forms a new departure in the gradual unfolding of nature's predestined plan in any case we have to try to square our views with the facts not the facts with our views and while one of the facts is that man stands unique in a park the other is that man is a scion of a progressive simian stalk naturalists have exposed the pit whence man has been digged and the rock whence he has been hewn but it is surely a heartening encouragement to know that it is an ascent not a descent that we have behind us there is wisdom in Pascal's maxim it is dangerous to show man too plainly how like he is to the animals without at the same time reminding him of his greatness it is equally unwise to impress him with his greatness and not with his lowliness to leave him in ignorance of both but it is very profitable to recognize the two facts 3. Man's pedigree the facts of anatomy physiology and embryology of which we have given illustrations all point to man's affiliation with the order of monkeys and apes to this order is given the name primates and our first and second question must be when and whence the primates began the rock record answers the first question primates emerged about the dawn of the Eocene era when grass was beginning to cover the earth with a garment their ancestral home was in the north in both hemispheres and then they migrated to Africa, India, Malay and South America in North America the primates soon became extinct and the same thing happened later on in Europe in this case however there was a re-peopling from the south in the lower Eocene and then a second extinction in the upper Pliocene there is considerable evidence in support of Professor R.S. Lull's conclusion that in southern Asia Africa and South America the evolution of primates was continuous since the first great southward migration and there is of course an abundant modern representation of primates in these regions today as to the second question whence the primates sprang the answer must be more conjectural but it is a reasonable view that carnivores and primates sprang the one order diverging towards flesh-eating and hunting on the ground the other order diverging towards fruit-eating and arboreal habits there is no doubt that the insectifors including shrews, tree-shrews, hedgehog mole and the like were very plastic and progressive mammals what followed in the course of ages was the divergence of branch after branch from the main primate stem first they diverged the South American monkeys on a line of their own and then the old world monkeys such as the macaques and baboons ages passed and the main stems gave off in the oligocene period the branch now represented by the small antherpoid apes the gibbon and the siamang distinctly later they diverged the branch of the large antherpoid apes the gorilla, the chimpanzee and the orang that left a generalized humanoid stock separated off from all monkeys and apes and including the immediate precursors of man when this sifting out of a generalized humanoid stock took place remains very uncertain some authorities referring it to the myocene others to the early Pliocene some would estimate its date at half a million years ago others at two millions the fact is that questions of chronology do not as yet admit of scientific statement we are infirmer though still uncertain ground when we state the probability that it was in Asia that the precursors of man were separated off from the monkeys and apes began to be terrestrial rather than arboreal professor lull points out that Asia is nearest to the oldest known human remains in java and that Asia was the seat of the most ancient civilizations and the original home of many domesticated animals and cultivated plants the probability is that the cradle of the human race was in Asia man's arboreal apprenticeship at this point it will be useful to consider man's arboreal apprenticeship how he became a terrestrial journeyman professor wood jones has worked out very convincingly the thesis that man had no direct four-footed ancestry but that the primate stock to which he belongs was from its first divergence arboreal he maintains that the leading peculiarities of the immediate precursors of man were wrought out during a long arboreal apprenticeship the first great gain of arboreal life on bipedal erect lines not after the quadrupedal fashion of trees loss for instance was the emancipation of the hand the foot became the supporting and branch gripping member and the hand was set free to reach upward to hang on by to seize the fruit to lift it and hold it to the mouth and to hug the young one close to the breast the hand the set free has remained plastic a generalized not a specialized member much has followed from man's handiness the arboreal life had many other consequences it led to an increased freedom of movement of the thigh on the hip joint to muscular arrangements for balancing the body on the leg to making the backbone a supple yet stable curved pillar to a strongly developed collar bone which is only found well formed when the forelimb is used for more than support and to a power of opposing the thumb and the big toe to the other digits of the hand and foot an obvious advantage for branch gripping but the evolution of a free hand made it possible to dispense with protrusive lips and gripping teeth thus began the recession of the snout region the associated enlargement of the brain box and the bringing of the eyes to the front the overcrowding of the teeth that followed the shortening of the snout was one of the taxes on progress of which modern man is often reminded in his dental troubles another acquisition associated with arboreal life was a greatly increased power of turning the head from side to side a mobility very important in locating sounds and in exploring with the eyes furthermore there came about a flattening of the chest and of the back and the movements of the middrift or diaphragm came to account for more in respiration than the movements of the ribs the sense of touch came to be of more importance and the sense of smell of less the part of the brain receiving tidings from hand and eye and ear came to predominate over the part for receiving olfactory messages finally the need for carrying the infant among the branches must surely have implied an intensification of family relations and favored the evolution of gentleness it may be urged that we are attaching too much importance to the arboreal apprenticeship since many tree loving animals remain today very innocent creatures to this reasonable objection there are two answers first that in its many acquisitions the arboreal evolution of the humanoid precursors of man prepared the way for the survival of a human type marked a great step in brain development and second that the passage from the humanoid to the human was probably associated with a return to mother earth according to professor lull to whose fine textbook organic evolution 1917 we are much indebted climatic conditions in Asia in the Miocene or early Pliocene were such as to compel the descent of the prehuman ancestor from the trees a step which was absolutely essential to further human development continental elevation and consequent eridity led to a dwindling of the forest and forced the ape man to come to earth and at last arose the man according to Lull the descent from the trees was associated with the assumption of a more erect posture with increased liberation and plasticity of the hand with becoming a hunter with experiments towards clothing and shelter with an exploring habit and with the beginning of communal life it is a plausible view that the transition from the humanoid to the human was affected by a discontinuous variation of considerable magnitude which is nowadays called a mutation and that it had mainly to do with the brain and the vocal cords but given the gains of the arboreal apprenticeship the stimulus of an enforced descent to terra firma and an evolving brain and voice we can recognize accessory factors which help success to succeed perhaps the absence of great physical strength prompted reliance on wits the prolongation of infancy would help to educate the parents in gentleness the strengthening of the feeling of kinship would favor the evolution of family and social life of which there are many anticipations at lower levels there is much truth in the saying man did not make society society made man a continuation of the story will deal with the emergence of the primitive types of man the gradual ascent of the modern species end of section 8