208 NATURAL HISTORY. 



Questions. What is said of the Lizard tribe ? What are the chief 

 families ? Where are the Chameleons found ? What are their char- 

 acteristics ? What is said of their tongues ? Of their eyes ? Of their 

 changing color ? Of their air-sacs ? What is said of the Geckos ? 

 What of the Iguana family? Of the Iguanodon? Of the Flying 

 Dragon ? Of the Monitors ? What is said of the true Lizards ? 

 What of the Snake Lizards ? Of the Naked-eyed Lizards ? What 

 are the peculiarities of the Snakes or Serpents ? What is said of their 

 skeleton ? How does a serpent execute its movements ? What is said 

 of the senses of Serpents ? What are the two classes of Serpents ? 

 What is the great peculiarity of the Viperine class ? What are its two 

 families ? What animals are mentioned as belonging to the Viperi- 

 da3 ? What is said of the Crotalida ? What are the two families of 

 the Colubrine Snakes ? What is said of the Colubers ? What of the 

 Boas ? What does the order of Amphibia include ? From what does 

 their name come ? What is said of their metamorphosis ? How do 

 they differ from other reptiles ? What is said of their tongues ? 

 What are their families ? What is said of the Frogs ? Of the Toads ? 

 Of the common Newt ? Of the Salamanders ? Of the Sirens ? 



CHAPTER XX. 



FISHES. 



347. THE Fishes constitute the second division of cold- 

 blooded Vertebrates. They are the only vertebrated an- 

 imals that are fitted to live entirely in the water. All 

 the peculiarities of their structure have reference to this 

 mode of life. These I will proceed to point out. 



348. All animals must breathe in order to live ; that 

 is, they can not live unless they have the blood exposed 

 to the action of the air. This is as true of Fishes as it is 

 of other animals. They breathe the air mingled with 

 water, and can not live in water that has no air in it. 

 This can be proved by experiment. If a fish be put into 

 a close vessel, it soon uses up all the air in the water ; 

 and it dies if more air be not introduced into the water 

 by unclosing the vessel. A fish dying in this way may 

 be truly said to be drowned. 



