The Universal Kinship

by J. Howard Moore

The most important class of animals arising out of the worms, on account of their distinguished offspring, were the hypothetical cord animals. The only existing species allied to these animals is the amphioxus, a strange, unpromising-looking creature, half worm and half fish, found in the beach sands of many seas. It has white blood and a tubular heart. It is without either head or limbs, and looks very much like a long semitransparent leaf, tapering at both ends. But it has two unmistakable prophecies of the vertebrate anatomy: a cartilaginous rod, pointed at both ends, extending along the back, and above this, and parallel to it, a cord of nerve matter. These are the same positions occupied by the spinal column and spinal cord in all true vertebrates. That the amphioxus is a genuine relative of the ancestor of the vertebrates is also shown by the fact that these simple forms of column and cord possessed by amphioxus are precisely the forms assumed by the spinal column and spinal cord in the embryos of all vertebrates, including man.

From these quasi-vertebrates developed the fishes—first (after the scaleless, limbless lampreys) the sharks with spiny scales and cartilaginous skeleton, and after these the lung fishes and the bony fishes, with flat, horny scales and skeletons of bone. From the beginning of the Devonian age, when fishes first came into prominence, till the rise of the great reptiles in the Triassic time, fishes were the dominant life of the sea. In the fishes first appeared jaws, a sympathetic nervous system, red blood, backbone, and the characteristic two pairs of limbs of vertebrates.

The lung fishes (Dipneusta), a small order of strange salamander-like creatures which live ingeniously on the borderland between the liquid and the land, may be looked upon as physiological, if not morphological, links between the fishes and the frogs. They combine the characters of both fishes and frogs, and zoologists have been tempted to make a separate class of them, and place them between the two classes to which they are related. They are like fishes in having scales, fins, permanent gills, and a fish-like shape and skeleton. They resemble frogs in having lungs, nostrils, an incipiently three-chambered heart, a pulmonary circulation, and frog-like skin glands. There are three genera with several species. One genus (Neoceratodus) is found in two or three small rivers of Queensland, Australia; another (Protopterus) lives in the Gambia and other rivers of Africa; and the third (Lepidosiren) inhabits the swamps of the Amazon region. They all breathe ordinarily by means of gills, like true fishes, but have the habit of coming frequently to the surface and inhaling air. The air-bladder acts as an incipient lung in supplementing respiration by gills. They all live in regions where a dry season regularly converts the watercourses into beds of sand and mud. During the season of drought these strange animals build for themselves a cocoon or nest of mud and leaves. This cocoon is lined with mucus, and provided with a lid through which air is admitted. Here they lie in this capsule throughout the hot southern summer, from August to December, breathing air by means of their lungs and living upon the stored-up fat of their tails, until the return of the wet season, when they again live in the rivers and breathe water in true piscatorial fashion. These capsules have often been carried to Europe, and opened 3,000 miles from their place of construction without harming the life within.

Here, in these eccentric denizens of the southern world, we find the beginnings of a grand transformation—a transformation in both structure and function, a transformation made necessary by the transition from life in the water to life in the air, a transformation which reaches its maturity in the higher air-breathing vertebrates, where the simple air-sac of the fish becomes a pair of lobed and elaborately sacculated lungs, performing almost exclusively the function of respiration, and the gills change into parts of the ears and lower jaw.

The air-bladder of ordinary fishes, which is used chiefly as a hydrostatic organ to enable the fish to rise and fall in the water, is probably the degenerated lung of the lung fishes.

From the lung fishes or allied forms developed the amphibians, the well-known fish quadrupeds of our bogs and brooks. The amphibians are genuine connectives—living links between the life of the sea and the life of the land. In early life they are fishes, with gills and two-chambered hearts. In later life they are air-breathing quadrupeds, with legs and lungs and three-chambered hearts. Here is evolution, plenty of it, and of the most tangible character. And it takes place right before the eyes. The transformation from the fish to the frog is, however, no more wonderful than the embryonic transformations of other vertebrates. It is simply more apparent, because it can be seen. The lungs of amphibians and the lower reptiles are simple sacks opening by a very short passage into the mouth. Some amphibians, as the axolotl of Mexican lakes, ordinarily retain their gills through life, but may be induced to develop lungs and adapt themselves to terrestrial life by being kept out of the water. Others, as the newts, which ordinarily develop lungs, may be compelled to retain their gills through life by being forced to remain uninterruptedly in the water. The black salamander, inhabiting droughty regions of the Alps, brings forth its young bearing lungs, and only a pair at a time. But if the young are prematurely removed from the body of the mother and placed in the water, they develop gills in the ordinary way. These are remarkable instances of elasticity in the presence of a varying environment.

In the amphibians the characteristic five-toed or five-fingered foot, which normally forms the extremities of the limbs of all vertebrates except fishes, is first met with. It was this pentadactyl peculiarity of the frog, inherited by men and women through the reptiles and mammals, that gave rise to the decimal system of numbers and other unhandy facts in human life. The decimal system arose out of the practice of early men performing their calculations on their fingers. This method of calculating is still used by primitive peoples all over the world. The sum of the digits of the two hands came, in the course of arithmetical evolution, to be used as a unit, and from this simple beginning grew up the complicated system of tens found among civilised peoples. It has all come about as a result of amphibian initiative. Our very arithmetics have been predetermined by the anatomical peculiarities of the frog’s foot. If these unthinking foreordainers of human affairs had had four or six toes on each foot instead of five, man would no doubt have inherited them just as cheerfully as the number he did inherit, and the civilised world would in this case be to-day using in all of its mathematical activities a system of eights or twelves instead of a system of tens. A system of eights or twelves would be much superior in flexibility to the existing system; for eight is a cube, and its half and double are squares; and twelve can be divided by two, three, four, and six, while ten is divisible by two and five only.

How helpless human beings are—in fact, how helpless all beings are! How hopelessly dependent we are upon the past, and how impossible it is to be really original! What the future will be depends upon what the present is, for the future will grow out of, and inherit, the present. What the present is depends upon what the past was, for the present has grown out of, and inherited, the past. And what the past was depends upon a remoter past from which it evolved, and so on. There is no end anywhere of dependence, either forward or backward. Every fact, from an idea to a sun, is a contingent link in an eternal chain.

From the amphibians (probably from extinct forms, not from living) there arose the highest three classes of vertebrates—the true reptiles, the birds, and the mammals—all of whom have lungs and breathe air from the beginning to the end of their days. Gills, as organs of breathing, disappear forever, being changed, as has been said, into parts of the organs of mastication and hearing. In the reptiles first appear those organs which in the highest races overflow on occasions of tenderness and grief, the tear glands. These organs are, however, in our cold-blooded antecedents, organs of ocular lubrication rather than of weeping. There are but four small orders of existing reptiles—snakes, turtles, lizards, and crocodilians. These are the pygmean descendants of a mighty line, the last of a dynasty which during the greater part of the Mesozoic ages was represented by the most immense and powerful monsters that have ever lived upon the earth. Mesozoic civilisation was pre-eminently saurian. Reptiles were supreme everywhere—on sea and land and in the air. Their rulership of the world was not so bloody and masterful as man’s, but quite as remorseless. Imagine an aristocracy made up of pterosaurs (flying reptiles), with teeth, and measuring 20 feet between wing-tips; great plesiosaurs (serpent reptiles) and ichthyosaurs (fish reptiles), enormous bandits of the seas; and dinosaurs and atlantosaurs, giant land lizards, 30 feet high and from 50 to 100 feet in length. A government of demagogs is bad enough, as king-ridden mankind well know, but dragons would be worse, if possible. The atlantosaurs were the largest animals that have ever walked upon the earth. They were huge plant-eaters inhabiting North America. It has been surmised that one of these behemoths ‘may have consumed a whole tree for breakfast.’ It was the mighty saurians of the Mesozoic time who brought into everlasting subordination the piscatorial civilisation of the Devonian and carboniferous ages.

Toward the latter part of the Reptilian Age, and somewhere along about the time of the appearance of hard-wood forests, came the birds, those beautiful and emotional beings who, in spite of human destructiveness, continue to fill our groves and gardens with the miracles of beauty and song. The bird is a ‘glorified reptile.’ How the ‘slow, cold-blooded, scaly saurian ever became transformed into the quick, hot-blooded, feathered bird, the joy of creation,’ is a considerable mystery, yet we know no reason for believing that the transformation did not take place. Although in their external appearance and mode of life birds and reptiles differ so widely from each other, yet, in their internal structure and embryology, they are so much alike that one of the brightest anatomists that has ever lived (Huxley) united them both into a single class under the name Sauropsida. It might naturally be supposed that the birds are descendants of the flying reptiles, the pterosaurs. But this may not be true. The pterosaurs were structurally much further removed from the birds than were certain extinct terrestrial reptiles. The fact that birds and pterosaurs both had wings has really nothing to do with the case. For the wings of reptiles, we almost know, were not homologous with the wings of birds. The bird’s wing is a feathered fore-leg; the wing of the reptile was an expanded skin stretching from the much-elongated last finger backwards to the hind-leg and tail. Wings, it may be remarked in passing, have had at least four different and distinct beginnings in the animal kingdom, represented by the bats, the birds, the reptiles, and the insects. This does not include the parachutes of the so-called flying squirrels, lemurs, lizards, phalangers, and fishes.