358 



NATURAL HISTORY. 



BATRACHIA. 



The frogs, toads, salamanders, and the like are called either Batrachia 

 or Amphibia ; the former being derived from the Greek word for frog, 

 while the latter has reference to the half-aquatic, half -terrestrial mode of 

 life of many of the forms. In the older works the Amphibia were grouped 

 • with the reptiles ; but now it is known that they are totally distinct. One 

 marked peculiarity of these animals is the metamorphosis which many of 

 them undergo. All of them, at least at one period of their life, breathe by 



Fig. 329. — Menobranchus (Necturus macvlatus). 



means of gills, just as do the fishes, and some of the species retain this 

 mode of respiration throughout the whole of their existence ; while in 

 others, the gills are absorbed, the gill-clefts close up, and then the lungs 

 and skin are the organs in which the blood obtains its supply of oxygen. 

 In the higher forms there are many other features introduced, which will 

 be alluded to farther on. 



One of the forms which retains its gills through life is that represented 

 in our first figure. So far as the writer is aware, it has no common name, 



