ON CHANGE OF MEXICAN AXOLOTL TO AN AMBLYSTOMA. 375 



me cogent enough. For sliould we even learn at a later time that the 

 Paris Axolotl also comes from a salt lake, which is exposed to winds 

 similar to those of the Lake of Mexico, yet there lies after all in these 

 peculiarities of the lakes only a force which renders difficult the meta- 

 morphosis of the larva and the gaining of a suitable new dwelling- 

 place on the land. The impossihility of attaining such a dwelling, or 

 indeed the total laclc of it, does not necessarily result from them. 



Evidently it would be a much more substantial support for my 

 hypothesis if I succeeded in pointing out forces in the physical relations 

 of the country wJiich entirely prechide tJie existence of AmUystoma there. 



