ON CHANGE OF MEXICAN AXOLOTL TO AN AMBLYSTOMA. 365 



A third case of the same kiud I find cited* by Seydig, in his essay, 

 "Ueber die Molche der Wiirtembergischen Fauna" (On the Salamanders 

 in the Fauna of Wiirtemberg), so rich in interesting detail. Sciireibers, 

 the former director of the Vienna Cabinet of Natural History, likewise 

 found " larvae'' of Triton with gills well developed, but of the size of " adult 

 males," and, as anatomical examination showed, with well developed 

 sexual organs, as well as ovaries filled with eggs. 



So, therefore, it is established that species which long ago attained 

 the stage of Salamandrida in the phyletic development may occasionally 

 sink back to the stage of Perennibranchiates. Evidentlj^, this fact makes 

 my view of the Axolotl as a form of reversion appear much less para- 

 doxical. Indeeil, the cases of reversion in the Triton are directly anal- 

 ogous to the transaction I suppose for the Axolotl. 



We only need suppose Amblystomas in the place of the Tritons, and 

 consider the swamp in which de Filtppi found his "sexually mature 

 Triton larvse" expanded to the Lake of Mexico, regarding, also, the un- 

 known, and perhaps in this case temporary, causes of the reversion as 

 permanent, and we have everything which is necessary to the restoration 

 of the Axolotl as we know it to day, ive obtain a Ferennibranchiate pojpu- 

 lation of the lake. 



It is not even yet determined whether, in that swamp of de Filippi 

 the Ferennibranchiate form of the Triton does not actually prevail per- 

 manently, for it has not, to my knowledge, been examined since in regard 

 to this subject. 



But if we assume for a moment that it actually were so, that a colony 

 of Ferennibranchiate Tritons lived there, carrying on reproduction sexu- 

 ally, should we wonder if occasionally, also, a genuine Triton came from 

 our brood, if we could succeed in stimulating most individuals of this 

 brood by removal into shallow water to the metamorphosis into Tritons ? 

 But just so it is according to my view with the Mexican Axolotl. 



But I need not limit myself to support my hypothesis, but must also 

 directly assail the tenability of the one hitherto held, for it stands in op- 

 position to facts. 



If we really had in the Axolotl a suddenly occurring phyletic further 

 development, then one fact would remain wholly incomprehensible, 

 namely, the sterility of the Amblystomas. 



Of about thirty Amblystomas which Dum^ril had obtained up to the 

 year 1870, full sexual maturity had not appeared in a single one ; neither 

 copulation nor the simple laying of eggs had taken place, and the indi- 

 viduals that were examined anatomically showed the eggs immature and 

 the spermatozoa present indeed, but without the undulating membrane 

 belonging to all the Salamandrida. They were not destitute of all power 

 of motion, but as Quatrefages stated, only moving imperfectly.t 



* Archiv f. Naturgescbichte (Archives for Natural History), 1867. 

 t Coinpt. Reud., t. Ixx, I'^TO. 



