Tht Transformation of the Mexican Axolotl. 609 



to the borders of the lake, at that time deep, with 

 precipitous sides and much less saline, not only 

 should we thus have presented different conditions 

 of life to those at present existing, but also such 

 as would be most favourable for the development 

 of a species of salamander. 



On the whole, I believe that my attempt to 

 explain the exceptional metamorphosis of the 

 Axolotl of the Mexican lake cannot be objected to 

 as being a too airy phantasy. In any case it is the 

 only possible explanation which can be opposed to 

 that which supposes that the occasional trans- 

 formation of the Axolotl is not reversion, but an 

 attempt at advancement. This last assumption 

 must, in my judgment, be rejected on purely 

 theoretical grounds by those who hold that a 

 sudden transformation of a species, when con- 

 nected with adaptation to new conditions of life, is 

 inconceivable by those who regard adaptation, 

 not as the sudden work of a magic power, but as 

 the end result of a long series of natural, although 

 minute and imperceptible causes. 



If my interpretation of the facts be correct, there 

 arises certain consequences which I may here 

 briefly mention in conclusion. 



First, with regard to more obvious results. If 

 Siredon Afexicanus, Shaw, only by occasional re- 

 version assumes the Amblystoma form, and never, 

 or only exceptionally, propagates as such, but only 

 as Siredon, the more recent systematists are not 



