468 



ZOOLOGY. 



phibians having a middle ear in addition to the internal ear 

 of fishes. In toads and frogs the tongue is quite free and 

 capable of being protruded, except in Pipa and Dactyle- 

 tlira, where it is entirely wanting. In other forms the 

 tongue is much as in fishes, not being capable of extension 



from the mouth. As in 

 fishes, there are no salivary 

 glands. The gills of Am- 

 phibians consist of two or 

 three pairs of branched, 

 fleshy appendages, which 

 grow out from as many 

 arches. While in the toad 

 and frog the gills are small 

 and remain but for a short 

 time, in the larval salaman- 

 ders, especially the axolotl 

 (Fig. 430), the gills are still 

 longer retained, while in 

 the mud-puppy (Necturus) 

 they persist throughout life. 

 The digestive canal is us- 

 ually simple, straight, there 

 being no enlargement form- 

 ing a stomach ; in other 

 species, both tailless and 

 tailed, the canal dilates into 

 a stomach, which in the 



toad lies across the body- 

 Fig. 430. Axolotl, or larval Salamander, ,,:.!-,, Tr> torliWlns 

 showing the gills, heart (II), aortic branches CftVlty. in t.lClpOlCS, 

 ami lungs (PA). P, pulmonary arteries ; ]: rlppovinp 1 

 M>, pulmonary veins ; A, bulbus arteriosms 11Ve Baying 

 from \yhich the vascular arches (B) origi- ma tter, the digestive tract 

 nate ; 66, branchial vein ; the lower A, vena o 

 cava ; V, descending aorta. From Gervais jg yei'V loil and closely COll- 

 et Van Beneden. -J 



ed (Fig. 431). 



The lungs are long, slender sacs, much like those of the 

 Dipnoan Lepidosiren, which extend backwards into the ab- 

 domen, as in the lizards and snakes, no diaphragm existing 

 to confine them in a thoracic cavity. The larynx exists in 

 a very rudimentary state, though the vocal powers of the 



