THE FROG 91 



A TAILLESS AMPHIBIAN. THE FROG 



Frogs and toads, which are the tailless, jumping amphibians, 

 belong to the order Salientia. The following descriptions will en- 

 able the student to identify the commonest species of frogs. 1 



Rana pipiens, the leopard frog. Green or brown, with large black 

 blotches edged with white or yellow, which lie in two irregular rows on the 

 back; legs barred above; belly pearly or yellowish; length about 2I inches; 

 lives in marshes or in the grass. 



Rana palustris, the pickerel frog. Brown or greenish, with several rows 

 of oblong square blotches on back and sides; length about 3 inches; com- 

 mon in cold springs or streams or in the grass. 



Rana clamitans, the green or spring frog. Green or brown, with rounded 

 spots all over the back ; legs with several cross bands ; beneath, pure white ; 

 length 3 inches; lives in ponds and streams. 



Rana catesbeiana, the bullfrog. Green or brown, with faint dark spots 

 above ; head often bright green ; beneath, pale blotches ; length 5 to 8 inches ; 

 lives in ponds and streams. 



Rana sylvatica, the wood frog. Pale reddish-brown; head small and 

 pointed, with a dark band on each side between eye and arm; length 

 1 \ inches; lives in the woods and in the grass. 



Three specimens will be needed for a complete dissection of the 

 frog : one for the outer form and the greater part of the internal 

 organs, including the heart and the blood vessels entering and 

 leaving it ; one for the other blood vessels ; and one for the skeleton. 

 The animals should be killed as needed, and preserved during the 

 dissection in a 5 per cent solution of formalin or in cold storage. 



Place the animal (alive if possible) under a glass or in a dissect- 

 ing pan and observe its form and color. The body is short and 

 compact, with a large head and mouth ; the hinder end is charac- 

 terized by the lack of a tail and by the great length of the hind 

 legs. The color is such as to adapt it to the environment in which it 

 lives, and may change from time to time, like that of a chameleon. 



The skin of the frog is without scales or other hardened integu- 

 mentary structures, such as are possessed by all vertebrates except 

 the caudate and salient amphibians. It is, however, provided with 



1 These descriptions have been modified from Pratt's "Manual of the Verte- 

 brates of the United States." 



