382 



METAZOAN PHYLA 



speaking, should be restricted to certain Old World reptiles which possess 

 several pronounced characteristics (Fig. 260). Among such character- 

 istics connected with arboreal life may be mentioned a lateral com- 

 pression of the body; the possession of a long prehensile tail which is not 

 easily broken and which if lost cannot be regenerated; and the existence 

 of long, slender limbs with digits so arranged that two are opposable 

 to the three others, making the foot effective in grasping. In each group 

 of digits, they are united nearly to their tips. The eyehds are united, 

 except for a small central opening. The eyes are capable of being moved 



Fig. 260. — Common chameleon of southern Europe, Chamaeleo vulgaris Daudin. (Based 



upon figure in Brehm, " Thierleben.") X %. 



independently and it is stated that the peculiar structure of the lids 

 makes it possible for the animal to locate objects very exactly. The 

 tongue, which is club-shaped and abundantly provided with a sticky 

 secretion, can be protruded to a distance of six inches or more. This 

 enables the chameleon to use its tongue for capturing insects, which 

 constitute its entire diet. Chameleons are generally oviparous, 

 although a few produce living young. They are famed for their power 

 of changing color, which is due to the presence of chromatophores in 

 the skin, affected both by outside stimuh and by stimulation by the 

 nervous system. 



415. Lizards. — The lizards are the most typical of the reptiles. 

 The hmbs are well-developed and modified for running, climbing, or 

 digging. Rarely limbs are absent, in which case the animal has very 



