4U8 



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 Pijxi, 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 

 gro-ff 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 2)ersist throughout life. 

 The digestive canal is us- 

 irally 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- 

 cavity. In tadpoles, which 

 live on decaying vegeta])le 

 matter, the digestive tract 

 is very long and closely coil- 

 ed (Fig. 431). 

 sacs, much like those of the 



Fig. 430.— ,4a'ofo^?, or larval Salamander, 

 ehovviiigthe gilln, heart iH), aortic branches 

 and lungs (PA). P, pulmonary arleries ; 

 pp, pidmonary veins ; A, bnlbus arteriot^us 

 from which the vas^cular arches (5) origi- 

 nate ; bb, branchial vein ; the lower .4, Acna 

 cava ; V, descending aorta. — From Gervais 

 et Van Beneden. 



The lungs are long, slender 



ab- 



Dipnoan Lejndosiren, which extend backwards into the 

 domen, as in the lizards and snakes, no diaphi-agm existing 

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

 it \ery rudimentary sttite, though the vocal powers of the 



