THE VERTEBRATA 153 



Efts. Belonging to the Tailed Amphibians also, 

 is the Axolotl, a creature found in the lakes of 

 Mexico, and in those of the Rocky Mountains. 



FlG. 43. Tadpoles, three-quarters of their natural size. A to D, 

 different stages of the Tadpole of the Common Toad, from 

 Epping Forest, England. , Tadpole of Peledytes punctatus, 

 dorsal view. 



It may or may not retain its gills; and forms 

 with gills, and forms without, may be found in 

 the same lake, each capable of laying eggs. 

 The two forms were at first described under 

 two different generic names : but when speci- 

 mens of the gill-bearing Siredon, kept in con- 

 finement, lost their gills, it was seen that they 

 became Amblystoma. There are other cases of 

 larval forms that produce young, and this curi- 

 ous occurrence is known as " paedogenesis." 



The Amphibia include the curious creatures 

 called Caeciliae (blind animals), or Gymnophiona. 

 They are snake-like in form, and are without 

 limbs; they burrow underground. Their real 

 place in classification was not found out at first, 

 but they were classed, by a wrong shot, with the 

 Reptiles. They are interesting as being the only 



