The Transformation of the Mexican Axolotl. 579 



Moreover, it is hardly permissible to seek such 

 an explanation, since Urodela are known which 

 have no gills in the adult state, and which never- 

 theless possess all the other characters of the Ic h- 

 thyodea, viz. want of eyelids, characteristic pala- 

 tine teeth, and the tongue bone. This is the case 

 with the genera Amphiuma (Linn.), Menopoma 

 (Harl.),and Cryptobranchus (v.d. Hoev.). The two 

 first genera, as is known, still possess gill-clefts, 

 but Cryptobranchus has even lost these clefts, 

 which, as in Amblystoma, are overgrown by skin ; 

 nevertheless Cryptobranchus is, according to the 

 concurrent testimony of all systematists, a true 

 salamander in habits, tongue bone, palatine 

 teeth, 17 &c. It must further be added that the 

 Axolotl itself can lose the gills without thereby 

 becoming transformed into an Amblystoma. I 

 have previously mentioned that in Axolotls which 

 were kept in shallow water the gills frequently 

 became diminutive, and it also sometimes happens 

 that they completely shrivel up. I possess an 

 Axolotl preserved in alcohol in which the gills have 

 shrivelled up into small irregular bunches, and the 

 dorsal crest is also so completely absent that its 

 place is occupied by a long furrow, and even on the 

 tail the crest has entirely disappeared from the 

 lower edge and about half from the upper edge. 

 Notwithstanding this, the creature is widely re- 

 moved from Amblystoma in structure ; it possesses 

 17 See Strauch, lot. cit. p. 10. 



