GENERAL ZOOLOGY 



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Fig. 18.15. Ichlhyophn, a limb- 

 less amphibian or caecilian. A, 

 adult in its burrow with a mass 

 of eggs. 5, young larva re- 

 moved from eggshell; note the 

 large external gills and the 

 copious yolk supply. C, older 

 larva after resorption of yolk 

 but before loss of the external 

 gills. (Redrawn from P. and F. 

 Sarasin, 1887-1890, Ergebmsse 

 natuTwissenschaJtlicher Forschungen 

 auf Ceylon, vol. 2.) 



of the past. They have survived like an entire group of "Hving fossils," 

 insofar as they represent the fishes that emerged to the land but returned to 

 water for their developmental stages. 



Among existing amphibians the most generalized are the Caudata, or tailed 

 forms, such as the salamander, Ambystoma (Fig. 18.14), and the mud puppy, 

 Necturus. Ambystoma lives most of the year upon the land, returning to water 

 for breeding in early spring. NecLurus can live only in the water, since it 

 depends on gills which are comparable with the external gills occurring tem- 

 porarily in the development of other amphibians. An extreme type among 

 the Caudata is the "Congo snake," Amphmma, of the southeastern United 

 States (Fig. 18.14). This animal may reach a length of 3 feet; its limbs are 

 so reduced that the heavy-bodied animal is snake-like in appearance. Another 

 large form is the "hellbender," Cryptobranchus, of the eastern United States 

 (Fig. 18.14). The largest of existing amphibians, attaining a length of almost 

 6 feet, is the giant salamander of Japan, Megalobatrachus. 



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