50 CHAMELEONS. 



eyes, which are very large and very projecting, are almost entirely 

 covered by the skin ; the light reaches them only through a little 

 hole, situate opposite to the pupil, and these organs move alto- 

 gether independently of each other. Their mouth is armed with 

 srt. all tri-lobed teeth, and their tongue, fleshy and cylindrical, is 

 extremely extensile : they can dart it out of the mouth to a dis- 

 tance that sometimes exceeds the length of the body, and they 

 use it to seize living insects upon which they feed. Their body 

 is compressed, and the back is ridged, or, as it were, trenchant, 

 and the skin is covered by small scaly granulations. These 

 singular animals are celebrated for their faculty of almost instantly 

 changing colour; and, if we believe the ancient writers, they even 

 possess the power of assuming successively, the hues of all the 

 objects by which they are surrounded, in order to conceal them- 

 selves more effectually from their enemies. The observations of 

 naturalists have already robbed the history of the Chameleon of 

 the fables with which it was loaded ; and, although the faculty of 

 changing its colours, in this manner, has been denied, it has been 

 ascertained that it really undergoes the most remarkable changes, 

 being sometimes almost white, sometimes yellowish, at other 

 times green, reddish, and even almost black, either entirely or 

 only on parts of the body. These changes are particularly 

 observed, when the animal is excited either by anger or by 

 heat. When it has remained lor some time in a dark, cold 

 place, it is almost white, and warming it, or stimulating it, 

 causes it to assume a bottle green, or vinous red hue, which 

 often becomes so intense that it appears to be almost black. 

 For a long time, these changes were attributed to the greater 

 or less distension of the very large lungs of this animal, and 

 to corresponding modifications in the quantity of blood sent 

 to the skin ; but we are assured, there is no necessary relation 

 between these phenomena ; and dissection of the skin teaches us 

 that we rmist seek the cause of these variations of colour in the 

 particular mode of the structure of this membrane. We find, in 

 tact, that it contains different colouring matters, some of which 

 can sometimes rise to the surface, and in a degree mask the 

 others, and at other times retire, and become hidden beneath th;. 

 superficial pigment. 



35. Only a single genus of Saurians, possessing the abv/e 

 described organization, is known ; but many species of Clw,ie- 

 leons have been ascertained. One of them, very common in 

 the neighbourhood of Algiers, is met with from Spain to the 

 Indies. 



N5. How many genera of Chameleons are known? 



