The Transformation of the Mexican Axolotl. 615 



there precluded the possibility of the existence of 

 Amblystomas. 



For a long time I was indeed unable to discover 

 such causes, and I therefore concluded the pre- 

 vious portion of this essay and went to press. 

 Afterwards, when residing in one of the highest 

 valleys of our Alps in the Upper Engadine, an 

 idea accidentally occurred to me, which I do not 

 now hesitate to regard as correct after having 

 tested it by known facts. 



It happens that in the Upper Engadine there 

 live only such Amphibia as persistently, or at 

 least frequently resort to the water. I found 

 frogs up to nearly 7000 feet above the sea, and 

 Tritons at 6000 feet (Pontresina and Upper 

 Samaden). On the other hand, the land-living 

 mountain salamander, S. Atra* was absent, al- 

 though suitable stations for this species were 

 everywhere present, and it would have wanted for 

 food as little as do its allies the water-newts. 

 Neither would the great elevation above the sea 

 offer any obstacle to its occurrence, since it occa- 



* [This species is interesting as being ovoviviparous, the 

 young passing through the branchiate stage within the body of 

 the mother. Some experiments, which were partially success- 

 ful, were made by Fraulein v. Chauvin with a view to solve 

 the question whether the branchiate stage could be prolonged 

 by taking the larvae directly from the mother before birth and 

 keeping them in water. See "Zeit. fur .wissen. Zoo." vol. 

 xxix , p. 324- R.M.] 



