Изображения страниц
PDF
EPUB

they are all limbless, unless we credit the little hind ciaws of some boas and pythons with the title of legs, they flow like swift living streams along the ground, using ribs and scales instead of their lost appendages, pushing themselves forward with jerks so rapid that the movement seems continuous. Without something on which to raise themselves they must remain at least half prostrate, but in the forest or on rough ground there are no lither gymnasts. Their united eyelids give them an unlimited power of staring, and, according to uncritical observers, of fascination; yet most of them seem to see dimly and hear faintly, trusting mainly for guidance to the touch of their restless protrusible tongue and to their sense of smell. Their only language is a hiss or a whine. Most of them have an annual period of torpor, and all periodically cast off their scales in a normally continuous slough, which they turn outside-in as they crawl out. Almost all lay eggs, but in a few cases (e.g. the adder) the young are hatched within the mothers, and this mode of birth may be induced by artificial conditions. Think not meanly of the serpent, "it is the very omnipotence of the earth. That rivulet of smooth silver-how does it flow, think you? It literally rows on the earth with every scale for an oar; it bites the dust with the ridges of its body. Watch it when it moves slowlya wave, but without wind! a current, but with no fall! all the body moving at the same instant, yet some of it to one side, some to another, or some forward, and the rest of the coil backwards; but all with the same calm will and equal way-no contraction, no extension; one soundless, causeless, march of sequent rings, and spectral procession of spotted dust, with dissolution in its fangs, dislocation in its coils. Startle it-the winding stream will become a twisted arrow; the wave of poisoned life will lash through the grass like a cast lance. It scarcely breathes with its one lung (the other shrivelled and abortive); it is passive to the sun and shade, and cold or hot like a stone; yet it can outclimb the monkey, outswim the fish, outleap the zebra, outwrestle the athlete, and crush the tiger.' It is a Divine hieroglyph of the demoniac power of the earth of the entire earthly nature. As the bird is the clothed power of the air, so this is the clothed power of the dust; as the bird is the symbol of the spirit of life, so this of the grasp and sting of death.”1

This well-known and eloquent passage is not perfectly true,thus the serpent breathes not scarcely but strongly with its one lung, but, while you may correct and complete it as you will, I am sure that you will find here more insight into the nature of serpents than in pages of anatomical description.

1 Ruskin's Queen of the Air.

A few snakes have mouths which do not distend, skull bones which are slightly movable, teeth in one jaw (upper or lower) only, and rudiments of hind legs. These are included in the genera Typhlops and Anomalepsis, and are small simple ophidians.

Many are likewise non-venomous snakes, but with wider gape and more mobile skull bones, and with simple teeth on both jaws. Some are very large and have great powers of strangling. Such are the Pythons, the Boa, and the Anaconda. To these our grass snake (Tropidonotus natrix) is allied.

Many poisonous snakes have large permanently erect grooved fangs in the upper jaw, and a salivary gland whose secretion is venomous. Such are the cobra (Naja tripudians), the Egyptian asp (Naja haje), the coral snakes (Elaps), and the sea snakes (Hydrophis).

Other poisonous snakes have perforated fang teeth, which can be raised and depressed. Such are the vipers (Vipera), the British adder (Pelias berus), the copperhead (Ancistrodon contortrix), the rattlesnakes (Crotalus).

Tortoises and Turtles (Chelonia).—Boxed in by a bony shield above and by a bony shield below, and often with partially retractile head and tail and legs, the Chelonians are thoroughly armoured. On the average the pitch of their life is low, but their tenacity of life is great. Slow in growth, slow in movement, slow even in reproduction are many of them, and they can endure long fasting. It is said that a tortoise walked at least 200 yards, twentyfour hours after it was decapitated, while it is well known that the heart of a tortoise will beat for two or three days after it has been isolated from the animal. In connection with their sluggishness it is significant that the ribs which help to some extent in the respiratory movements of higher animals are soldered into the dorsal shield, thus sluggish respiration may be in part the cause, as it is in part the result, of constitutional passivity. All the Chelonians lay eggs in nests scooped in the earth or sand.

The marine turtles (e.g. Sphargis, Chelone), the estuarine softshelled turtles (e.g. Aspidonectes), the freshwater turtles (e.g. Emys), and the snapping turtle (Chelydra) are more active than the land tortoises, such as the European Testudo graca, often kept as a pet. The tortoise of the Galapagos Islands (Testudo elephantopus), the river tortoise (Podocnemys expansa) of the Amazon, the bearded South American turtle (Chelys matamata), and the green turtle (Chelone mydas) attain a large size, sometimes measuring about 3 feet in length.

Crocodilians (Crocodilia).-Crocodiles, alligators, and gavials seem in our present perspective very much alike—strong, large, heavily armoured reptiles, at home in tropical rivers, but clumsy and stiff-necked on land, feeding on fishes and small mammals,

growing slowly and without that definite limit which punctuates the life-history of most animals, attaining, moreover, a great age, freed after youth is past from the attacks of almost every foe but man. The teeth are firmly implanted in sockets; the limbs and tail are suited for swimming, and also for crawling; the heart is more highly developed than in other reptiles, having four instead of three chambers. The animals lie in wait for victims, and usually drown them, being themselves able to breathe while the mouth is full of water, if only the nostrils be kept above the surface.

In many ways Reptiles touch human life, the poisonous snakes are very fatal, especially in India; crocodilians are sometimes destructive; turtles afford food and "tortoise shell;" lizards are delightfully beautiful.

8. Birds. What mammals are to the earth, and fishes to the sea, birds are to the air.

Has anything truer ever been said of

[graphic]

FIG. 55. The Collocalia, which from the secreted juice of its salivary glands builds the edible-bird's-nest. (Adapted from Brehm.)

them than this sentence from Ruskin's Queen of the Air? "The bird is little more than a drift of the air brought into form by plumes; the air is in all its quills, it breathes through its whole frame and flesh, and glows with air in its flying, like a blown

:

flame it rests upon the air, subdues it, surpasses it, outraces it ;is the air, conscious of itself, conquering itself, ruling itself."

Birds represent among animals the climax of activity, an index to which may be found in their high temperature, from 2°-14° Fahrenheit higher than that of mammals. In many other ways they rank high, for whether we consider the muscles which move the wings in flight, the skeleton which so marvellously combines strength with lightness, the breathing powers perfected and economised by a set of balloons around the lungs, or the heart which drives and receives the warm blood, we recognise that birds share with mammals the position of the highest animals. And while it is true that the brains of birds are not wrinkled with thought like those of mammals, and that the close connection between mother and offspring characteristic of most mammals is absent in birds, it may be urged by those who know their joyousness that birds feel more if they think less, while the patience and solicitude connected with nest-making and brooding testify to the strength of their parental love. Usually living in varied and beautiful surroundings, birds have keen eyes and sharp ears, tutored to a sense of beauty, as we may surely conclude from their cradles and love songs. They love much and joyously, and live a life remarkably free and restless, qualities symbolised by the voice of the air in their throat, and by the sunshine of their plumes. There is more than zoological truth in saying that in the bird "the breath or spirit. is more full than in any other creature, and the earth power least,' or in thinking of birds as the purest embodiments of Athene of the air.

[ocr errors]

But just as there are among mammals feverish bats with the power of true flight, and whales somewhat fish-like, so there are exceptional birds, runners like the ostriches and cassowaries, swimmers like the penguins, criminals too like the cuckoos and cow-birds in which the maternal instincts are strangely perverted. As we go back into the past, strange forms are discovered, with teeth, long tails, and other characteristics which link the birds of the air to the grovelling reptiles of the earth. Even to-day there lives a "reptilian-bird "—Opisthocomus-which has retained more than any other indisputable affinities with the reptiles. Professor W. K. Parker, one of the profoundest of all students of birds, described this form in one of his last papers, and there used a comparison which helps us to appreciate birds. They are among backboned animals what insects are among the backboneless-winged possessors of the air, and just as many insects pass through a caterpillar and chrysalis stage before reaching the acme of their life as a flying imago, so do the young birds within the veil of the eggshell pass through somewhat fish-like and somewhat reptile-like

[graphic]

FIG. 56.-Decorative male and less adorned female of Spathura-a genus of Humming-birds. (From Darwin, after Brehm.)

« ПредыдущаяПродолжить »