340 



GENERAL ZOOLOGY 



the presence, usually, of two short, rod-like organs, called 

 " balancers," which project from the anterior end of the body 

 near the mouth. The balancers may serve as sense-organs of 

 touch, or as adhesive disks, in addition to 

 the use suggested by their name. The gills 

 are usually visible externally for a longer 

 period than is the case with the toad and 

 the frogs. Some species retain their gills 

 throughout life, though the lungs are also 

 functional ; in others, though the gills are 

 absorbed in adult life, the gill-openings are 

 retained ; in still others all traces of gills 

 and gill-slits disappear; and, finally, a few 

 species lose their lungs also, when mature, 

 depending entirely upon the skin for res- 

 piration. 



Of the five species which retain their gills 

 throughout life, three are found in the sur- 

 face-waters of the eastern and southeastern 

 United States, and one in the subterranean waters of Austria 

 and Texas respectively. Both the cave-inhabiting species live 

 in absolute darkness, far below the surface of the earth, and 

 are colorless and blind. The white skin is sensitive to light, 

 and has been changed to a black color after several months of 

 exposure under ordinary conditions. Fig. 168 shows the Texan 

 cave salamander (TypJdomoVge rath'buni) from an artesian well 

 one hundred and eighty-one feet below the surface. 



The genus Amblydtoma includes some of the largest of 

 our species, known by the common name of blunt-nosed sal- 

 amanders. The color is black, spotted with yellow. As these 

 salamanders are protected by an acrid secretion from the 

 mucus-glands of the skin, the conspicuous colors are possi- 

 bly to be interpreted as warning coloration. The adults live 

 in damp places and lay eggs in the water in large masses 



FIG. 168. Cave Sala- 

 mander. Slightly 

 Reduced. (After 

 Eigenmann) 



