292 THE VERTEBRATE ANIMALS 



munity from attack because of their color markings. The feet of the tree 

 toad are modified for climbing by having little disks on the ends of the 

 toes, by means of which it is able to cling to vertical surfaces. 



Another common amphibian is the newt, a salamander. This smooth- 

 skinned, four-Umbed animal, often incorrectly called a lizard, passes its 

 larval Ufe in the water, where it breathes by means of external gills. Later 

 it loses its giUs, becomes provided with lungs, and comes out on land. 

 Its coat, which was greenish in the water, now becomes bright orange 

 in color. In this condition we sometimes find them crawling on wood 

 roads after a rain. After over two years' life on land, it again returns to 

 the water, becomes green with red spots (as seen in the Figure), and now 

 is able to reproduce its kind. Some salamanders never have lungs, but 

 breathe through the moist skin. 



Newt. From photograph loaned by the American Museum of Natural History. 



Still other amphibians are the mud puppies, sirens or mud eels, and the 

 axolotl. All of the above animals differ from the reptiles in having a 

 smooth skin with no scales, and in passing the early stage of their existence 

 in the water. 



Characteristics of Amphibia. — The frog belongs to the class of 

 vertebrates known as Amphibia. As the name indicates (amphi, 

 both, and bin, life), members of this group pass more or less of their 

 life in the water, although in the adult state they are provided with 

 lungs. In the earlier stages of their development they take oxygen 

 into the blood by means of gills. At all times, but especially during 

 the winter, the sldn serves as a breathing organ. The skin is soft 

 and unprotected by bony plates or scales. The heart has three 

 chambers, two auricles and one ventricle. Most amphibians 

 undergo a complete metamorphosis. 



Classification of Amphibia Mentioned 

 Oedee I. Urodela. Amphibia having usually poorly developed appendages. Tail 



persistent through life. Examples : mud puppy, newt, salamander. 

 Ohdee II. Anura. Tailless Amphibia, which undergo a metamorphosis, breathing 



by gills in larval state, by lungs in adult state. Examples : toad and frog. 



