WHAT AMPHIBIAN MEANS ' 5 



of the birds which liave invaded the air. With them 

 came in the three-jointed Hmb and the fingers and 

 the toes. Tlie many frino^es of the fins of the fishes 



Fig. 3. 



Slender csecilia 

 (Csecilia gracilis). 



White-bellied csecilia 

 {Cxcilia Jentaculata). 



rapidly decreased to five digits in this next class, and 

 then the human hand lay in its cradle among the 

 rushes — a giant which should rise and strike and 

 strangle. 



With the jointed limb and toe came in the lung, 

 also, in its best development — permitting the excur- 

 sion away from the water. 



There are now living three orders of amphibians, 

 easily distinguished from each other. First there are 

 the tailed forms, like the salamanders, always having 

 a tail and at least two limbs. Second there are the 



