TAILED BATRACHIANS 269 



temperature the eggs are retained, and the young are 

 born alive in an active condition. 



In spite of the fact that in captivity Proteus often 

 refuses to feed, it will thrive nevertheless vi^ithout taking 

 any form of nourishment at all for as long as five years. 

 The writer one day offered some of his specimens, which 

 had not fed since their captivity, a period of over two years, 

 some larvae of midgets ; these were at once greedily 

 accepted, and now the specimens in question feed weekly 

 with the greatest regularity. In its native haunts Proteus 

 is said to subsist entirely on small Crustacea. 



The members of the family Sirenid^ are characterized 

 by the absence of teeth in both jaws, which are covered 

 by a horny sheath. The body is long and eel-shaped ; 

 the fore limbs alone are present ; the external gills are 

 well developed. 



The family is represented by two genera, each with a 

 single species, namely. Siren and Pseudobranchus, both of 

 the South-Eastern United States ; in the former genus the 

 digits are four in number, in the latter, only three. 



The Siren, 5. lacertina, which is not unlike Amphiuma in 

 appearance, lives in shallow ponds and marshes, where it 

 grows to a length of four feet. In spite of its long external 

 gills the animal frequently leaves the water for short 

 periods. 



