The Transformation of the Mexican Axolotl. 627 



that the Axolotl hitherto known from the great 

 Mexican lake which never dries up (Lake of 

 Xochimilco and Chalco), is only met with in its 

 native habitat in the Siredon form, i.e. as Siredon 

 Humboldtii. According to Velasco the cause of 

 the frequent assumption of the Amblystoma form 

 by the new Siredon Tigrinus, is to be found in the 

 local conditions of life of this species. The Lake 

 Santa Isabel is shallow, its greatest depth amount- 

 ing to three meters, and it is liable to a periodical 

 drying up, which is so complete that one can pass 

 dry-shod through it in several places. The species 

 must therefore have long since died out had it 

 not been able to adapt itself periodically to a 

 land life. Now it could have become transformed 

 into a land Amphibian as Senor Velasco ob- 

 served at various stages of growth ; and indeed 

 this author believes that "the Creator has im- 

 planted an instinct in this creature," which enables 

 it to always undergo metamorphosis at the right 

 time. 



This last assumption may or may not be taken 

 as correct, but this much is established, viz. that 

 numerous individuals of this species take to the 

 land, and remain there during a period of many 

 months. 



But does this contain the proof that salamander- 

 like animals are actually able to lead a land life in 

 Mexico that the dry air is advantageous, or at 

 least supportable to them ? It does not appear so 



