CLASS AMPHIBIA: ORDEK ANUKA. 



179 



CLASS IV. AMPHIBIA. 



General Characteristics. Amphibians have a double 

 life an immature or tadpole stage passed in the water, 

 during which they breathe by gills; and a mature stage 

 passed in the air, during which they breathe by lungs. To 

 this metamorphosis there are a few exceptions, but the typi- 

 cal species lose the gills and tails by absorption, and develop 

 lungs and limbs. Some retain the tails and others the gills, 

 but all when mature have lungs. As a rule, the tadpoles 

 are herbivorous, the adults carnivorous. 



f" TAILS AND GILLS TRANSIENT. Anura, F. og, Toad, etc. 



AMPHIBIA. -I TAILS PERMANENT AND GILLS TRANSIENT. Urodela, Salam-inder, etc. 



(.TAILS AND GILLS PERMANENT. Amphipneusta, Siren, etc. 



ORDER ANURA. 



General Characteristics. The Tailless Amphibians 

 are distinguished by 

 their broad heads, naked 

 skin, prominent but 

 retractile eyes, and, in 

 the adult state, lack of 

 tails. The eggs are laid 

 and hatched in the 

 water. The young tad- 

 pole resembles a little 

 fish, with a large head 

 and compressed tail, 

 but no limbs. Soon 

 gills (branchiae) appear; 

 and then small, vascu- 

 lar tufts aid respiration 

 by extracting air from 

 the water that passes 



through the mouth and 



OUt Of temporary Slits. Tadpole changes. 



Fig. SOU. 



Skeleton of a Frog. 

 Fig. 305. 



