TAILED AMPHIBIANS 265 



(Proteus anguineus), which inhabits the water of subterraneous caverns in 

 Carniola and Dalmatia. Passing its life in perfect darkness, the animal 

 is completely blind (compare with mole), and its skin colourless (compare 

 with tape-worm and cockchafer grub). The skin, being very thin, allows 

 the blood-corpuscles (see Part I., p. 7) to be seen through the body walls, 

 and the animal thus appears flesh-coloured. The feet are short and weak, 

 and quite useless for locomotion, and the body is accordingly elongated 

 and vermiform (see p. 232, Section 2). As the animal never leaves the 

 water, it retains its swimming-tail throughout life, as well as external 

 branchiae, in addition to lungs ; in short, it remains in the larval 

 condition of the higher amphibians. 



The Mexican Axalotl, which is often kept in aquaria, is a larval 

 form which breeds in that condition in the Lake of Mexico. If forced to 

 leave the water, however, it loses the external gills and the fin-membrane 

 of the tail, and becomes a terrestrial form known as Amblystoma. In 

 the United States the transformation occurs regularly. 



