572 Studies in the Theory of Descent. 



reached, although later, in its native country ? Or 

 is it inconceivable that the sudden removal from 

 8000 feet above the sea (Mexican plateau) to the 

 altitude of Paris, may have given the respiratory 

 organs an impetus in the direction of the transfor- 

 mation imminent ? In all probability we have here 

 to do with the direct action of changed conditions 

 of life." 



That the substance of this last statement must 

 still hold good is obvious from the experiments pre- 

 viously described, which show that by the applica- 

 tion of definite external influences, we have it to a 

 certain extent in our power to produce the trans- 

 formation. It is precisely in this last point that 

 there lies the new feature furnished by these ex- 

 periments. 



But are we also compelled to interpret the phe- 

 nomenon in the above manner ? i. e. as a sudden 

 advance in the phyletic development of the species 

 occurring, so to speak, at one stroke ? I believe 

 not. 



What first made this view appear to me erro- 

 neous, was the appearance of the living Amblys- 

 tomas bred from my Axolotl larvae. These creatures 

 by no means differed from the Axolotls merely in 

 single characters, but they were distinct from 

 the latter in their entire aspect ; they differed in 

 some measure in all their parts, in some but 

 slightly and in other parts strongly in brief, they 

 had become quite different animals. In accord- 



