VERTEBRATA. 259 



eat the fish or animals that the fish wants to eat. 

 Hugh Miller, the self-taught geologist, observed this 

 change of colour in the Flounder, without having 

 seen the fact recorded in any book : a circumstance 

 which should afibrd a useful hint to self-taught 

 naturalists. A similar arrangement in the Cattle-fish 

 has already been referred to. Something of the same 

 kind happens in the Frog, which changes colour to a 

 certain extent ; and the most remarkable instance of 

 change of colour occurs in the reptile called the 

 Chamseleon. The colour changes of the latter were 

 perhaps exaggerated in the descriptions which were at 

 first given by travellers, but they are, nevertheless, of 

 a remarkable character. It is interesting to observe 

 these cases of a similar kind occurring in animals 

 difi'ering so widely from each other as the cuttle-fish,, 

 flounder, frog, and reptile ; in each of them the pur- 

 pose is the same, to enable the animal to escape- 

 detection by approximating to the colour of its sur- 

 roundings. These instances show how similar cir- 

 cumstances of life may impart a superficial similarity 

 regarding one characteristic to animals of widely dif- 

 fering origin. It is probable that in all these animals 

 changes of colour are excited by anger or fear ; and it 

 is interesting to compare the way in which human 

 beings show different feelings by blushing or turning 

 pale : in this case the nerves act on the blood-vessels, 

 instead of acting on pigment cells of the skin, as in 

 the other cases. 

 The order of fishes called Mud-fislies, or Dipnoi, 



