AMPHIBIANS. 106 



grow until it became nearly as large as the other hind leg. 

 I believe (I cannot be sure, for this happened eight or nine 

 years ago) the new leg from the first was perfectly shaped. 

 However, I was glad to prove the truth of report without 

 having been cruel enough to make an amputation. 



The tanks in which tritons are kept should be carefully 

 covered, or the animals will be certain to escape, and perhaps 

 cause some annoyance to the ladies of the household. 



There is a peculiar kind of water lizard — ^found pi-incipally 

 in the lake close to the city of Mexico — which is of unusual 

 interest, not only in the aquarium, but to all who have any 



Fig. 85. Mexican Axolotl (Siredon pisciformis). 



liking for natural history. This strange animal is commonly 

 called the Mexican Axolotl, and scientifically named Siredon 

 pisciformis (Fig. 85). In shape it is something similar to 

 a three-month-old newt ; that is, a young triton which has 

 developed all its legs, but which still retains its branchise. 



The Axolotl may be described as the tadpole of the 

 Amblystome (Ambly stoma mexicanus) (Pig. 86) ; but for a 

 long time it was considered to be an animal which retained its 

 branchise throughout its existence, like the Siren or Proteus, 

 and was therefore placed among the Perenni-branchiata or 

 retainers of branchiae through life. The Axolotl when full 

 grown is about 9ia. or lOin. long, and rather stoutly built. 

 It is of a very dark slate-colour, and covered with black 

 spots, and in the earlier part of its existence it is not 



