This singular family of Saurians have the head wide and flattened, the mouth wide, the nostrils distant and lateral, the eyes large, with short lids; the tongue short, fleshy, and capable of slight elongation. The body is thick and short, low on the legs, rather squat and depressed, with a belly trailing on the ground; back without crest. The skin is defended by granular scales, interlaced with others of a tubercular character; they are almost always of a sombre colour. Their feet are short, wide apart, and robust; they are furnished on the upper part with imbricated laminæ, which enable them to adhere firmly to the surface of even the smoothest bodies, and to run with rapidity in all directions on a plain surface, and even to remain stationary with the back downwards, like the common house Fly. More generally, however, their hooked and retractile claws, like those of cats, assist them in climbing, crawling up trees, rocks, and even perpendicular walls, and to remain there immovable for several hours. Their flexible bodies mould themselves into the depressions of the surface of the earth, in which they become scarcely visible, their natural colour blending, and being confounded with, the colour of the soil. Their eye-balls, which dilate and contract considerably, protect them from the action of the sun's rays, and enable them, it is thought, to see in the dark. They are nocturnal, avoid the sun's rays, and catch their food in the chinks of rocks. Their movements are rapid, silent, and sudden. They hibernate, and are provided with fatty masses in the groin which are supposed to be a provision for their nourishment during that period. Geckos emit sounds which resemble the noise an equestrian makes when he would encourage his horse—smacking their tongues on the palate to produce the sound. They seek habitations in which they can find food, and are timid, inoffensive, and quite incapable of inflicting injury either by their bite or claws; but their repulsive appearance makes them objects of general repugnance, and has caused evil properties to be attributed to them. Thus people try to destroy them by every possible means. There are about sixteen known species of Geckos distributed in all quarters of the globe, but chiefly in warm countries.
Fig. 31.—Platydactylus homalocephalus.
[The Geckotidæ are divided into many genera, according to the construction of the toes. Duméril refers to the comparative shortness and general structure of the feet and conformation of the toes, which he describes and figures in detail. The lower surface and the sole he states are very dilatable, and furnished with small plates or lamellæ, following or overlying each other in a mode which varies in the different species. The nails are sometimes wanting on all the toes, but more frequently hooked, and more or less retractile; the toes sometimes united at the base, and in Platydactylus the extremity of the toe expands into a fan shape, as in the Tree Frogs. The membranous and soft plates of the lower surface of the toes have various modifications in different genera, which have been made the basis of their arrangement. The Wall Gecko is supposed by Gesner to be the Lizard spoken of by Aristophanes and Theophrastus, and the Tarentula of the Italians: and there is little doubt that it was the Αακαλαβωνμε of Aristotle and the ancient Greeks; it clambered about their walls catching spiders, on which it fed. Schneider has shown it was the Stellio of Pliny. Linnæus mentions three species, which he places with his great genus Lacerta. Modern herpetologists, following Cuvier and Duméril, class them according to the structure under the several genera Ascalabotes, Platydactylus, Hemidactylus, Ptyodactylus, Thecadactylus, Stenodactylus, and Gymnodactylus.]
The Wall Gecko (P. homalocephalus), [Fig. 31], is of an ashy grey colour, as if powdered on the upper part of the body. It is white underneath, and inhabits the islands of the Mediterranean, as well as the countries which form the basin of that sea, such as Italy, France, Spain, and Africa. They are generally found in old walls; they are, however, sometimes seen running on those of modern habitations. They feed on all sorts of insects, particularly on the dipterous insects and Arachnidans.
Chameleo. (Laurenti.)
The genus Chameleo, of which ten species are described in the British Museum Catalogue, are natives of Africa and Asia and naturalised in Southern Europe. They live on trees, clinging to the branches by their feet and prehensile tails; they move slowly and with great caution, feeding upon insects, which they catch with singular dexterity by the rapid elongation of their tongue, which is viscid at the tip.
Certain groundless metaphors, deeply rooted in the popular mind, have singularly distorted the truth in respect to these reptiles. It is commonly believed that the Chameleon often changes its shape, that it has no fixed colour belonging to itself, but takes that of all objects which it approaches. This singular idea has descended from very ancient times. According to the reports of Theophrastus and Plutarch, the Chameleon takes all colours in turn but white; according to Aristotle it changes colour all over the body; but Ælian seems to have had views more in accordance with those of modern observers, for he says when it takes other colours than grey and disguises itself, it covers only certain parts of the body with them. Altogether the ancients made the Chameleon a very fantastic animal; hence in the familiar comparisons of literature these fabulous beings serve as a type to designate uncertain principles; to paint fawning men, who have neither character nor individuality of their own, but who bend themselves to the will and adopt the opinions of others. Putting aside the imaginary attributes accorded to the Chameleon by the fancies of the ancients, and painting them such as they are, we still see in them animals most worthy of observation and highly interesting to the naturalist, as well for the singular formation of different parts of their bodies as for their remarkable habits, and even for peculiarities which have given some sanction to the errors and prejudices to which we have alluded.
Chameleons have compressed bodies; the back round and projecting, or rather pyramidal; the skin granulated; the head angular, with salient occiput resting on a short and thick neck; their legs are slender; the hind, as well as the fore toes are five; the tail prehensile and round. The eyes are very large and protruding, their globes covered by a single shagreen-like eyelid, which the animal can dilate or contract at will, but which leaves little liberty to a small hole pierced at the centre, through which a quick and rather brilliant eye-ball is perceived. The eyes, in the Chameleon, are thus completely enveloped, as if they were too delicate to sustain any glaring light; but this is not all—their eyes have a singular mobility. By certain special muscular arrangements they have the power to direct them on objects either together or separate. Sometimes they turn their eyes in such a manner that one eye looks back and the other forward. With one eye they can see objects above them, while with the other they can see those situated below. It is a common saying in France, applied to the Chameleon, "that it could look into Champagne and see Picardy in flames."
The vermiform and retractile tongue is also a most singular organ. It is cylindrical, about six inches long, terminating in a fleshy, dilatable, and somewhat tubular tip, which is covered with a glutinous secretion, by the aid of which it seizes its insect food, and draws it towards its mouth. The feet have five very long and almost equal strong and hooked claws, but the skin of the legs extends to the end of these toes, and unites them in a very peculiar manner. Not only is this skin attached to each of the toes, but it envelops them, and forms, as it were, two bundles,—the one of three fingers, and the other of two. From this structure one can anticipate the extreme difference which exists between the habits of Chameleons and those of Lizards. These two bundles of long toes are placed in such a manner as to enable them to seize the branches easily on which they love to perch; they can grasp these branches by holding on with one bundle of fingers before, and the other behind, in the same manner as Woodpeckers, Cuckoos, and Parrots. Chameleons are better able to preserve their equilibrium upon trees than upon the ground; consequently they are more often seen in those ærial domiciles. Besides, their long and strong prehensile tail serves them as a fifth limb. They swing themselves about like monkeys, grasping the small branches, and thus saving themselves from falling. Moreover, they are cautious, moving at all times very slowly when going from one branch to another. Walking becomes much more difficult for them when they rest upon a level surface—groping their way as they advance, placing their feet upon the earth, one after the other, with the greatest circumspection. They also steady themselves on the ground by the aid of their tail. In their walk they display a certain gravity which contrasts with their diminutive size and the agility which might be expected from them. Even when perched upon a tree their movements exhibit a slowness and deliberation that one would be inclined to say was affected. It is true that the arrangement of their eyes, and the rapid movements of their tongue, render personal activity superfluous in their search for food. They can see their prey and their enemies from a great distance, and in all directions. The latter they readily avoid. As to their prey, when about to seize it, the Chameleon rolls round its extraordinary eye-balls so as to bring them to bear on the devoted object. As soon as it arrives within range of the tongue, that organ is projected with unerring precision, returning into the mouth with the prey adhering to the viscous tip. This tongue they can extend to a length sometimes surpassing that of their body. The skin of the Chameleon does not adhere to the muscles everywhere; some spaces are left free, into which the air penetrates, causing the skin to heave and swell; this mechanism is voluntary, the animal having the power of inflating or relaxing it at pleasure. When this great living bladder is emptied, the animal may be said to resemble a bag of gold-beaters' skin filled with bones. Chameleons exhibit great variation in their colours; that is to say, they may be almost white, sometimes yellowish, at other times green, reddish, and even black, either in portions, or all over their bodies. These changes of colour were for a long time attributed to the greater or less distention of the vast lungs they possess, and to the corresponding modifications in the quantity of blood sent to the skin; but this explanation is now abandoned. According to Mr. Milne Edwards, the cause of these variations of colour lie in the peculiar structure of their skin, in which there exists two layers of membranous pigment, placed the one above the other, but disposed in such a manner as to appear simultaneously under the cuticle, and at other times so that the one hides the other. Again, occasionally the cuticle is hidden under the superficial pigment.