ZOOLOGY FOR MEDICAL STUDENTS 



CHAP. 



AMPHIBIA 



SCHEME OF CLASSIFICATION 



I. TRODKLA (Tailed Amphibians). 



Cryptobranchus, Awphiuma, Amblystoma, Salaniandra, Triton, 



Necturus, Proteus, Siren. 

 II. APODA (or Gymnophiona Burrowing., legless Amphibians). 



Coecilia. Hypogeophis, Epicrium. 

 III. ANURA (Tailless Amphibians Frogs and Toads). 

 Raua. Hnfo. liyla. 



The Amj)hil)ia form the first subdivision of the Tetrapoda. What 

 mav he regarded as the normal form of body is that exemplified by a 

 Xe\vt (Triton Fig. 177, A). From this the Apoda and the Anura have 

 departed in different directions. The former (Fig. 180, B) have taken 



to a burrowing mode of life like that 

 of an Earthworm, and in correlation 

 with this the body has become very 

 long and cylindrical,, bluntly pointed 

 at each end, and the limbs have 

 completely disappeared except for 

 minute and transient vestiges in 

 the embryo. In the Anura Frogs 

 and Toads (Fig. i8o ; A) on the 

 other hand the body has become 

 specialized for leaping : the hind- 



B 



FIG. 1 80. 



ni in the Amphibia. A, leaping type (Fro- Rana) ; B, burrowing 

 type (one of th,- Apoda llyfogeophis). 



limbs have become greatly developed, their attachment has become 

 .slutted tar forwards so as to shorten the trunk region, while the tail, 

 "id protocercal in the larva or tadpole, atrophies and disappears 

 "miplctcly as the adult form is reached. 



I he skin has, except for inconspicuous vestiges in a few members 



''"up. lost all trace of the scales present in the fishes. Its 



"" :m.l smooth, and is kept moist by the secretion of 



