Page:Encyclopædia Britannica, Ninth Edition, v. 14.djvu/761
LIZARD 737
Elizabeth's time. The late Mr Krefft has made the observation that this lizard when startled, rises with the forelegs off the ground, and squats and jumps in kangaroo-fashion, thus reminding us of the peculiar locomotion ascribed to certain gigantic extinct reptiles. The other lizard is one which most appropriately has been called Moloch horridus. It is covered with large and small spine-bearing tubercles; the head is small, and the tail short. It is sluggish in its movements, and so harmless that its armature and (to a casual observer) repulsive appearance are its sole means of defence. It grows only to a length of 10 inches, and is not uncommon in the flats of South and West Australia.
Fig. 5. – Frilled Lizard (Chlamydosaurus).
The majority of the ground-agamas, and the most common species of the plains, deserts, or rocky districts of Africa and Asia, belong to the genera Stellio and Agama. They resemble much the Grammatophora of the Australian region, their scales being mixed with larger prominent spines, which in some species are particularly developed on the tail, and disposed in whorls. Nearly all travellers in the north of Africa mention the Hardhón of the Arabs (Stellio cordylinus), which is extremely common, and has drawn upon itself the hatred of the Mohammedans by its habit of nodding its head, which they interpret as a mockery of their own movements whilst engaged in prayer. Uromastyx is one of the largest and most developed genera of ground-agamas, and likewise found in Africa and Asia. The body is uniformly covered with granular scales, whilst the short, strong tail is armed with powerful spines disposed in whorls. The Indian species (U. harderickii) feeds on herbs only; the African species probably take mixed food.
Fig. 6. – Forefoot of Chamæleon o'shaughenesii.
The Chamæleons are almost peculiar to the African region, and most numerous in Madagascar, where out of the thirty-six species known not less than seventeen occur. Only one species (C. vulgaris) extends into India and Ceylon. No other member of the order of lizards shows such a degree of specialization as the chamæleons. The tongue, eyes, limbs, tail, skin, lungs are modified in a most extraordinary manner to serve special functions in the peculiar economy of these animals. They lead an exclusively arboreal life; each of their feet is converted into a grasping hand, by means of which, assisted by a long prehensile tail, they hold so fast to a branch on which they are sitting that they can only with difficulty be dislodged. Their movements are slow on the ground, and still more so in the water, where they are nearly helpless. As in ant-eaters, woodpeckers, or frogs, their tongue is the organ with which they catch their prey; it is exceedingly long, worm-like, with a club-shaped viscous end; they shoot it out of the mouth with incredible rapidity towards insects, which remain attached to it, and are thus caught. The globular eyes are covered with a circular lid pierced by a small central hole, and are so prominent that more than one-half of the ball stands out of the head. Not only can they be moved in any direction, but each has an action independent of the other; one eye may be looking forwards, whilst an object behind the animal is examined with the other. The lungs of the chamæleons are very capacious, and are inflated when the animal is angry or frightened. The faculty of changing colour, which they have in common with many other lizards, is partly dependent on the degree in which the lungs are filled with air, and different layers of chromatophores are pressed towards the outer surface of the skin. Some species are only a few inches long, whilst others attain to a length of 18 and 20 inches. The majority are oviparous, a few ovoviviparous.
Fig. 7. – Lower Surface of the Toe of (a) Gecko, (b) Hemidactylus – enlarged.
Almost all the lizards belonging to the family of Geckos may be recognized at first sight; the head is broad and depressed, the eyes large, the body depressed; the tail is thick at the base, tapering, generally somewhat deformed, as a specimen is rarely met with in which this member is not reproduced. The limbs are stout, rather short, with at least four of the toes well developed. Geckos are found in almost every part of the globe between and near the tropics, frequenting houses, rocks, and trees; and some of the species are so numerous around and within human dwellings as to be most familiar objects to the inhabitants. Many are able to run up and along the surface of a wall or of any other perpendicular object; for this purpose the lower surface of their toes is provided with a series of movable plates or disks,[1] by the aid of which they adhere to the surface over which they pass. In forest-species this apparatus is generally less developed, or entirely absent, claws being of greater use for walking up the rough bark of a tree. Geckos, with few exceptions, are nocturnal and, consequently, large-eyed animals, the pupil being generally contracted in a vertical direction, shaped like two rhombs placed with the angles towards each other. They are of small size, the largest species not exceeding 10 or 14 inches in length. They are carnivorous, destroying moths and all kinds of insects, and even the younger and weaker members of their own species. They have been seen devouring the skin which they cast off, and
- ↑ The mechanism resembles in some the adhesive organ of Echeneis or sucking-fish, in others that of the legs of a fly.