AMPHIBIANS 



363 



when they would immediately withdraw. The 

 little toads remained motionless, "well knowing 

 that quick movements, or a show of escape, 

 would most likely induce the tortoise to a 

 hasty snap, with consequences to be regretted 

 by both." The expression "well knowing" 

 must be taken with reservations, as the action 

 is doubtless instinctive. 

 We usually distinguish the frogs from the toads by 



the fact that the first are smooth and more generally 



aquatic, the second rough 



or warty, and in the adult 



stage often found far from 



water. This separation is 



satisfactory only for the 



most common forms. The 



typical frogs have teeth in 



the upper jaw, but none 



in the lower jaw, while 



the typical toads have no 



teeth in upper or lower 



jaw. The tree frogs or 



Hylidse have more or less 



enlarged adhesive disks at 



the ends of the toes, which 



enable them to climb with 



ease and safety. 



Photograph by E. R. Sanborn, N. Y. Zool. Soc. 

 FIG. 142. Giant tree frog. 



References 



GADOW, H. "Amphibia and Reptiles." Cambridge Natural History, 1901. 



MARSHALL, A. MILNES. The Frog; An Introduction to Anatomy, Histology, 

 and Embryology. Edited by G. H. Fowler (Macmillan). This author re- 

 marks : "The tadpole is really a fish ; not merely in its habits, but in its 

 mode of breathing, in the arrangement of its heart and its blood vessels, 

 and, indeed, in almost every detail of its organization." 



PICKERSON, M. C. The Frog Book. Doubleday, Page & Co. 



