234 



BRANCH CHORDATA 



Phaneroglos'sa. — This group is characterized by the presence 

 of a tongue and by distinct Eustachian tubes. It includes the 

 toads and frogs. Gadow estimates 900 species in the world. 

 Frogs and toads have tails in the larval or tadpole (Fig. 194) 

 condition, but are tailless in the adult stage. The body is 

 short and stout. They have a small number of trunk vertebrae 

 and the caudal vertebrae are replaced by one long bone, the uro- 

 style. They have four limbs, the posterior ones, long, strong, and 

 adapted for leaping or hopping. Toads are crepuscular and 



nocturnal. They hibernate in the 

 mud at the bottom of the water. 

 The tadpole or "pollywog" is 

 fish-like and aquatic. It has a 

 long tail and breathes by gills. 

 Its intestine is very long, adapt- 

 ing it to its vegetable food. 



Fig. 193. — Dactyl'ethra capen- 

 sis. (Claus.) 



Family Bufon'idae. — Toads are 

 clumsy, stout-bodied, nocturnal insect- 

 feeders. The tongue is fixed by the 

 anterior end and can be thrust out to 

 catch its food. They have no teeth. 

 The skin is warty or glandular and 

 secretes a fluid for protection. The 

 toes are webbed, but not dilated at the 

 tips. Toads resemble the ground verj' 

 closely. 



The American toad (Bu'fo lentigino'- 

 svs) is familiar to all. The young are 

 nearly smooth, 1 he adults warty. They 

 are brownish-olive, with a yellowish 

 median line and brown spots. There is a bony ridge behind and above 

 the eye and two black patches below the eye. The tympanum is large. 



Family Hy'lidae or Tree Frogs. — These are arboreal frogs with an op- 

 posing thumb and with adhering disks on the end of each toe, by which 

 they cling to the trees in which they live. 



Our most common example is the northern tree-frog ( Hy'la ver' sicolor) of 

 the eastern United States and Canada. It is about 2 inches long and deli- 

 cately colored. " Its color passes within a short time from dark brown or 

 olive gray to pale gray or white, occasionally retaining a few large dark 

 patches on the back and delicate cross-bars on the limbs." It has small 

 warts, which produce an acrid secretion. It is found not over 20 feet from 

 the ground in trees or on lichen-covered stone fences. Its color renders 

 it almost perfect in protcH'tive resemblance. One may be within a foot of 

 it and not be able to distinguish it. It croaks noisily in the evening or 

 just before a rain. In croaking its vocal sacs swell to enormous pro- 

 portions. It remains quiet in the shade during the day, but is lively in 



