236 



AMPHIBIA. 



covering. In general, tliey are enveloped in a 

 transparent glaire or jelly. 



The organization of the skeleton, as well as 

 other peculiarities in the anatomy, manifest that 

 the Amphibia are formed on a grade of structural 

 development, inferior to that of the Enoplia, 

 The skull is united to the spine by two processes, 



SKELETON OF FROG. 



or condyles, instead of one, the ribs are either 

 rudimentary or altogether wanting, and the 

 sternum or breast-bone is imperfectly developed, 

 or absent. 



" To any person," observes Professor Bell, " ca- 

 pable of appreciating the interest attached to the 

 study of physiological phenomena, the contempla- 

 tion of an animal, which, at one period of its life, 

 is endowed exclusively with the organs of aquatic 

 respiration, resembling the gills of fishes, with 

 means of locomotion adapted only to a con- 



