128 



REPTILES AND BIRDS. 



some spaces are left free, into which the air penetrates, causing the 

 skin to expand ; this mechanism is voluntary, the animal having the 

 power of inflating or relaxing it at pleasure. Chameleons exhibit 

 great variation in their colours ; that is to say, they may be almost 

 white, sometimes yellowish, at other times green, reddish, and even 

 black, either in portions, or all over their bodies. These changes of 

 colour were for a long time attributed to the greater or less distension 

 of the vast lungs they possess, and to the corresponding modifications 



Fig. 31. — Common Chameleon. 



in the quantity of blood sent to the skin ; but this explanation is now 

 abandoned. According to M. Milne-Edwards, the cause of these 

 variations of colour lie in the peculiar structure of their skin, in which 

 there exists two layers of membranous pigment, placed the one above 

 the other, but disposed in such a manner as to appear simultaneously 

 under the cuticle, or at other times to contract so that the one hides' 

 the other. Again, occasionally the cuticle is hidden under the 

 superficial pigment. 



[Sixteen or seventeen species of Chameleon are described in the 

 British Museum Catalogue. 



I. — Having an erect fin on the back, the belly crested ; which 

 includes the Fringed Chameleon, C. crzstatus, a native of Fernando Po. 



