468 



ZOOLOGY. 



phibians having a middle ear in addition to the internal ear 

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

 capable of being protruded, except in Pijiu and Dadylc- 

 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 jjairs of branched, 

 fleshy appendages, which 

 grow out from as many 

 arches. "\Miile 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, vrhile in 

 the miid-puppy {Xectnnis) 

 they persist throughout life. 

 The digestive canal is us- 

 ually simple, there being no 

 special enlargement form- 

 ing a stomach ; in other 

 species, both tailless and 

 tailed, the canal dilates into 

 a stomach, which in the 

 toad lies aci oss the body- 

 cavity. In tadpoles, which 

 live on decaying vegetable 

 matter, the digestive tract 

 is very long and closely coil- 

 ed (Fig. 431). 



sa^s, much like those of the 

 Dipnoan Lepidosiren, which extend backwards into the ab- 

 domen, as in the lizanls and snakes, no diaphi'agm existing 

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

 a very rudimentary state, though the vocal powers of the 



Fig. 430— ATolotl. or Hrval Salamaniler, 

 ehowingthe L'ills, heart (/?), aortic branches 

 and lllnfjs ^/-'.ll. P^ pulmonary an cries ; 

 pp. pulmonary veins ; A, bnlbns arteriosus 

 from which the vascular arches (fi) origi- 

 nate : bb, branchial \ein ; the lower A. \ eni 

 cava ; F, descending aorta.— From Ccrvais 

 et Van Bcneden. 



The lungs are Ions;-, slender 



