The Transformation of the Mexican Axolotl. 571 



has remained at an inferior stage of phyletic 

 development. 



All zoologists " who have expressed an opinion 

 upon the transformation of the Axolotl, and 

 who are not, like the first observer of this fact, 

 embarrassed by Cuvier's views as to the immuta- 

 bility of species, regard the phenomenon as though 

 a species, which owing to some special conditions 

 had hitherto remained at a low stage of develop- 

 ment, had now through some other influences been 

 compelled to advance to a higher stage. 



I believed for a long time that the phenomenon 

 could not otherwise be comprehended, so little was 

 I then in a position to bring all the facts into har- 

 mony with this view. Thus in the year 1872 I 

 expressed myself as follows ls : " Why should not 

 a sudden change in all the conditions of life (trans- 

 ference from Mexico to Paris) have a direct action 

 on the organization of the Axolotl, causing it sud- 

 denly to reach a higher stage of development, such 

 as many of its allies have already attained, and 

 which obviously lies in the nature of its organiza- 

 tion a stage which it would perhaps itself have 



11 [Eng. ed. Seidlitz is an exception, since in his work on 

 Parthenogenesis (Leipzig, 1872, p. 13) he states that " In the 

 Axolotl, Paedogenesis, which is not in this case .... mono 

 gamous, but sexual, and indeed gynaekogenetic, has already 

 become so far constant that it has perhaps entirely super- 

 seded the orthogenetic reproduction."] 



u Uber den Einfluss der Isolirung auf die Artbildung. 

 Leipzig, 1872, p. 33. 



P p 



