CHAMELEONS are distinguished by having the eyelids united and pierced by a central aperture. Also each eye moves independently of the other. Their tails are very long and prehensile; they are well suited for climbing and for a life among trees. Many of them are sluggish in bodily movement, but they catch their insect food by darting out their long tongues so rapidly that they seldom miss their object.
They are proverbially noted for their power of changing colour. This is due to the presence of mobile pigment cells, but though they undoubtedly have this power it must be understood that the process is gradual and not subject to any violent transformation. It is usually governed by their environment and state of health.
Crocodiles have the fourth canine tooth in the lower jaw longer than the others. It is received into a notch in the upper jaw and is visible when the mouth is closed. In the case of alligators this tooth fits into a pit in the upper palate and consequently is hidden when the mouth is shut. With crocodiles the hind-feet are completely webbed, with alligators only partially. Alligators are found only in the warm parts of North and South America, whilst crocodiles are more widely distributed. The Indian crocodile sometimes attains a length of twelve feet, whilst the Nilotic variety, which is very common, has been known to measure as much as fifteen feet. The Caimans of South America are probably the largest of all, having been found so long as twenty feet.