CLASS amphibia: okdee anuea. 



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 bi-eathe 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. 



'Tails and gills transient. Anura, Fi og, Toady etc 



AMPHIBIA.- Tails PERMANENT AND GILLS TRANSIENT. Urodela, Salamander, etc. 



Tails and gills feruanunt. 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 (branchiffi) 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. 



Skeleton of a Frog. 

 Fig. SOB. 



