CHAPTER XVI 



Amphibia 



The familiar amphibia are the toads, frogs, and salamanders. 

 As the name indicates, they Hve two Hves, one in the water and the 

 other on land. The majority of the amphibia lay their eggs in 

 water and the larvae breathe by gills, while the adults breathe by 

 lungs. Some adult amphibia have persistent gills, however. 

 Amphibia are of considerable economic importance, toads being 

 particularly beneficial in capturing insects. 



Classification 



Amphibia. (Gr., " leading a double life.") 



Apoda or Coecilians. (Legless amphibians found in the tropics.) 



Urodela or Caudata. (Salamanders.) 



Anura or Salientia. (Tailless toads and frogs.) 



Characteristics 



1. Skin smooth, moist and devoid of scales. 



2. Limbs penta-dactylic or with five toes. 



3. Skull articulates with the first vertebra by two occipital condyles, 



and is composed of very few bones. 



4. Lungs are present except in a few cases. 



5. Heart has three chambers, a ventricle and two auricles. 



6. Most of the species undergo a metamorphosis, the young living 



in the water and breathing by means of gills. As the lungs 

 become functional these gills disappear, except in a few of 

 the lower amphibia. 



7. As a rule, the Amphibia are aquatic or semi-aquatic In habits, 



and even when they live far away from the water during 

 most of the year, they nearly always go to the water in the 

 spring to deposit their eggs. 



8. Amphibians are confined to the torrid and the temperate zones. 



In the temperate zone they hibernate when cold weather 

 sets in. 



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