60 THE COLOURS OF ANIMALS 



CHAPTEE V 



PROTECTIVE RESEMBLANCES IN VEETE- 

 BE AT A, ETC. 



MANY of the lower Vertebrata have the power of 

 rapidly modifying their colour according to the en- 

 vironment, and these will be described in a future 

 chapter. Such a power appears to be possessed by 

 few reptiles, and by no bird or mammal. 



Protective Resemblances among Reptiles 



Our two English snakes are well concealed by 

 their colours ; the olive-green Grass Snake (Tropi- 

 donotus natrix) harmonising well with the grassy banks 

 which it chiefly frequents; while the brown viper 

 (Pelias berus) is difficult to detect upon the dry heaths 

 where it is most commonly found. Our lizards are 

 also well protected in the same manner. 



Protective Resemblances among Birds 



Wallace has directed attention to the protective 

 colours of female birds which build open nests, and he 

 points out that the males are similarly protected when 



