Some persons have imagined that the variation of colour depends on the wants and passions of the animal. This is not the case. The change is often caused by mental emotion, but is not dependent on it; and I believe that the animal has no control whatever over its colour. The best proof of this assertion may be found in the fact that my own Chameleon changed colour several times after its death; and, indeed, as long as I had the dead body before me, changes of hue were taking place. The food of the Chameleon consists of insects, mostly flies, which it catches by means of its tongue, which can be protruded to an astonishing distance. The tongue is nearly cylindrical, and is furnished at the tip with a slight cavity, which is filled with a very glutinous secretion. When the Chameleon sees a fly or other insect, it gently protrudes the tongue once or twice, as if taking aim, like a billiard-player with his cue, and then, with a moderately smart stroke, carries off the insect on the glutinous tip of the tongue. The force with which the Chameleon strikes is really wonderful. My own specimen used to look for flies from my hand, and at first I was as much surprised with the force of the blow struck by the tongue as I was with the grasping power of the feet. [Illustration: THE GECKO. FOOT OF THE GECKO--UNDER SIDE.] So much for the Chameleon. We will now take the NILOTIC MONITOR and the LAND MONITOR, the other reptiles which have been conjectured to be the real representatives of the Koach. These lizards attain to some size, the former sometimes measuring six feet in length, and the latter but a foot or so less. Of the two, the Land Monitor, being the more common, both in Palestine and Egypt, has perhaps the best claim to be considered as the Koach of Scripture. It is sometimes called the Land Crocodile. It is a carnivorous animal, feeding upon other reptiles and the smaller mammalia, and is very fond of the eggs of the crocodile, which it destroys in great numbers, and is in consequence much venerated by the inhabitants of the country about the Nile. The theory that this reptile may be the Koach of Leviticus is strengthened by the fact that even at the present day it is cooked and eaten by the natives, whereas the chameleon is so small and bony that scarcely any one would take the trouble of cooking it. The Gecko takes its name from the sound which it utters, resembling the word "geck-o." It is exceedingly plentiful, and inhabits the interior of houses, where it can find the flies and other insects on which it lives. On account of the structure of the toes, each of which is flattened into a disk-like form, and furnished on the under surface with a series of plates like those on the back of the sucking-fish, it can walk up a smooth, perpendicular wall with perfect ease, and can even cling to the ceiling like the flies on which it feeds.