LIFE, IN ITS HIGHER FORMS.

No. III.

REPTILES.

LIKE the FISHES and the AMPHIBIANS, the animals of which we have now to speak are cold-blooded: that is, their power of producing heat in the process of breathing is so small, that their temperature scarcely rises above that of the medium, whether air or water, in which they reside. Like FISHES, they are mailed; their bodies are protected by a hard and dry skin, which takes the form of overlapping scales, or compact broad plates or shields, or, as in some of the Lizards, a combination of these two. They increase by eggs, which are laid singly, and are always enveloped in a calcareous covering, which, according to the greater or less ratio of the earthy element, is a parchment-like skin, or a hard and brittle shell. In the latter case, the eggs have a close resemblance to those of BIRDS. In several respects there is an advance in organisation over the AMPHIBIANS; the heart is composed of two auricles and one ventricle; the respiration is performed by means of lungs exclusively; and there is no metamorphosis in the Class, the animals presenting the perfect form even from the egg.

There is more diversity in form and structure among the animals that compose this Class than among those of any other of the great Vertebrate Division. Look at the ponderous Tortoise enclosed in an unyielding box, with an orifice in front and behind just large enough to allow him to poke out his head and limbs. Look at the grim Crocodile lurking in the river reeds, with his enormous jaws bristling with conical teeth, his body covered with bony shields, and

his lashing serrated tail. Look at the Chameleon running on the leafy twig, with his shagreen coat, his great inflated head, his long tongue shot out to capture a distant fly, and his slender tail-tip coiled round the branch to hold fast. And finally, look at the tortuous Snake as he lies basking on the sunny bank, in gleaming scales, darting out his forked tongue in play see how he lies in twisted coils; and now mark how, footless and limbless as he is, he glides away on alarm, leaving only an undulating trail in the dust where he passed!

Surely all these various creatures are not formed on the same model! Surely there can be no community of structure here which can bind together into one group forms so remotely diverse! Yes, diverse as they are, they possess characters in common, which more than outweigh their differences, and the whole are united into a chain of many links, which by a beautiful gradation conduct us from one to the other.

Many of these animals are more or less noxious; and some of them are terribly fatal to other creatures and to man himself; hence, a certain amount of popular prejudice against the whole Class exists, and the innocent, which far out-number the noxious, share the reputation, and are visited with the hatred and aversion due to their malific fellows. Yet there are points in their history, which make them not unworthy of our attention. The changeable lustre of many, especially of the tropical Lizards and Snakes; the elegance and grace of their movements; the provisions made for their defence in their formidable weapons; peculiarities in their organisation whereby they are fitted for their appointed spheres and habits ;-these and many other details which our space forbids us even to enumerate here, render the study of herpetology no less attractive than any other branch of natural science.

HOW SERPENTS CREEP.

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The Serpent may be considered as the characteristic form of this Class of beings; at least our thoughts more spontaneously recur to the lithe and winding Snake, than to any other shape, when the word Reptile is pronounced, as indeed the idea of creeping * is most perfectly realised in the gliding movements of an animal absolutely without limbs.

There is something exceedingly interesting in this very action. The rapid gliding of a Snake is performed by means of the numerous ribs (which in the skeleton look like the feet of a Centipede), and the broad plates (scuta) which go across the belly. The action and the discovery of its nature are described by Sir Everard Home in the following words::"When the Snake begins to put itself in motion, the ribs of the opposite sides are drawn apart from each other, and the small cartilages at the end of them are bent upon the upper surfaces of the abdominal scuta, on which the ends of the ribs rest; and as the ribs move in pairs, the scutum under each pair is carried along with it. This scutum, by its posterior edge, lays hold of the ground and becomes a fixed point from whence to set out anew. This motion is beautifully seen when a Snake is climbing over an angle to get upon a flat surface. When the animal is moving, it alters its shape from a circular or oval form to something approaching a triangle, of which the surface on the ground forms the base. The Coluber and Boa having large abdominal scuta, which may be considered as hoofs or shoes, are the best fitted for this kind of progressive motion.

An observation of Sir Joseph Banks, during the exhibition of a Coluber of unusual size, first led to this discovery. While it was moving briskly along the carpet, he said he thought he saw the ribs come forward in succession,

*The words herpetology, reptile, serpent, creep, have all one erivation is their common parent.

like the feet of a caterpillar. This remark led me to examine the animal's motion with more accuracy, and on putting the hand under its belly, while the Snake was in the act of passing over the palm, the ends of the ribs were distinctly felt pressing upon the surface in regular succession, so as to leave no doubt of the ribs forming so many pairs of levers, by which the animal moves its body from place to place."

Many of the Serpents habitually live among the branches of trees, and most species can climb the smooth trunks with facility; not, however, by encircling the branch or bole in spiral coils, as artists who probably never saw a Snake in motion ridiculously represent them, but by a direct upward gliding, the body extended nearly in a straight line.

As all the Serpent tribes are carnivorous, and almost all feed on living active animals, often of much greater bulk than the diameter of their own mouths, while yet they invariably swallow their prey entire, it becomes a problem of interest how this is effected. They are fitted for their work by a peculiar mode of articulation in the bones of the head. All the bones of the skull are very loosely put together, but the jaws are remarkably expansible. In the first place, the lower jaws are much longer than the skull, commencing behind its base; secondly, they are not hinged to the upper jaw, but are suspended at the end of a pair of long slender bones, which are attached to the hind part of the skull by muscles and tendons so as to be very moveable; thirdly, the two branches of the lower jaw, which in higher animals are soldered, as it were, together, are in the Serpents simply bound by ligaments. The result of the whole arrangement is that the mouth is capable of a most enormous expansion.

Most of our readers are familiar with descriptions of the mode in which the great tropical Snakes,-the Boas of the

West, or the Pythons of the East,-take and gorge their prey. A Serpent, whose body at its largest part does not exceed the thickness of a footman's leg, and whose head is not wider than a lady's hand, will readily swallow a goat. We say "readily," because the process is regular and ordinary, but it is slow and tedious, and painful to read of, and much more to witness. We will not repeat the details here, but merely allude to a contrivance by which the function of breathing is allowed to proceed during the protracted interval of swallowing, when the whole throat of the Serpent is distended almost to bursting by the descending prey, and the whole head and jaws appear irremediably dislocated. These animals are furnished with peculiar muscles for bringing forward the larynx, or entrance to the windpipe, during the action of swallowing, as has been demonstrated by Mr. Joseph H. Green; and Mr. Broderip has observed that the larynx is at such a time protruded as much as a quarter of an inch beyond the edge of the dilated lower jaw.*

Most Serpents master their prey by open violence; and the large species of the tropics embrace it in repeated coils of their bodies, which are then contracted with great muscular force, so as to crush and compress their victim to death. But other kinds are furnished with a more securely fatal power, in the presence of two long, hooked, tubular teeth in the upper jaws. These teeth, or fangs, are open at each extremity, and the base communicates with a vesicle, which is a reservoir of powerful poison, secreted by glands spread over the cheeks. When a Rattlesnake or a Viper makes its attack, it commonly elevates the head and draws it somewhat back; then with lightning rapidity it strikes forward, piercing its enemy with the projecting fangs; at the same instant the poison-bag, which has been just filled by the secretion, poured forth under the excitement of rage, "Zool. Journal," ii.