6 1 8 Studies in the Theory of Descent. 



of the Upper Engadine, Rana Temporaria the 

 brown grass frog, is there much more a frequenter 

 of the water than in the plains. It is true that I 

 can find no remark to this effect in the excellent 

 work of Fatiot, already referred to above, and I 

 am therefore obliged to resort to my own observa- 

 tions, which, although often repeated, have always 

 been carried on for only a short time. I was 

 much struck with the circumstance that the Enga- 

 dine frogs were to be found in numbers in the 

 water long after the pairing season, which, ac- 

 cording to Fatiot, lasts at most to the end of June. 

 In the numerous pools around Samaden I found 

 them in July and August, whilst in the plains they 

 only take to the water at the time of reproduction, 

 and seek winter quarters in the mud on the first 

 arrival of this season. (Fatiot, p. 321.) In the 

 Engadine they have therefore in some measure 

 adopted the mode of life of the aquatic frogs, but 

 this of course does not prevent them from re- 

 turning in damp weather to their old habits and 

 roving through meadows and woods. 



After these considerations had made it appear 

 to me very probable that the dry air of the Upper 

 Engadine accounted for the absence of the black 

 land-salamander, the question at once arose 

 whether the absence of Amblystomas from the 



w Rana esculenta never reaches Alpine regions, this species 

 not having been found higher than noo meters. (Fatiot, 

 loc. cif.,p. 318). 



