CLASS REPTIUA 551 



and interclavicles; the eyelids are united into a single fold with 

 a small central opening; the eyes are moved separately, causing 

 the animal to squint. The tongue is club-shaped and covered 

 by a sticky secretion; it can be projected by muscles and by 

 the inflow of blood to a distance of over six inches, and is used 

 like that of the frog (p. 480, Fig. 410) for capturing live insects 

 which constitute its entire food. The skin is covered with 

 granules; it is shed several times a year, coming off in large 

 flakes when the body is rubbed against stones or the limbs of 

 trees. 



One of the features that has made the chameleons famous is 

 the power of rapidly changing their colors. This is brought 

 about with the aid of chromatophores (see p. 522) and is ap- 

 parently partly under the control of the animal and partly due 

 to external stimuli, such as light and temperature. 



A few chameleons are viviparous, but most of them deposit 

 their eggs in the ground. In northern Africa the animals be- 

 come fat in the autumn and hibernate in the ground during the 

 winter. 



The common chameleon of North Africa, Syria, and Asia 

 Minor is Chameleon mdgaris (Fig. 452). It is usually greenish 

 in color and reaches a length of from eight inches to a foot, about 

 half of which consists of the tail. 



Suborder 2. SAURIA. -- LIZARDS. - -The lizards constitute a 

 very diversified group of reptiles. They usually have an elon- 

 gated body and four well-developed limbs that are used for run- 

 ning, clinging, climbing, or digging. Some have no limbs or only 

 vestiges, but the pectoral and pelvic girdles are always present 

 and there is usually a trace of a sternum. The tail is generally 

 long; it is easily broken off, but a new organ is soon regenerated, 

 which, however, does not possess vertebrae. The eyelids are 

 movable except in some of the degenerate burrowing forms in 

 which the eyes have become concealed beneath the skin. The 

 skin is covered with small scales. 



Lizards are in most cases oviparous, and the eggs are pro- 



