614 Studies in the Theory of Descent. 



of the phenomenon. In the first place these 

 seemed to me too local, since they could only be 

 applied with any certainty to the Axolotl of the 

 lake of the Mexican capital, whilst the Paris 

 Axolotls obtained from other parts of Mexico 

 still required an explanation. On the other hand, 

 these causes did not appear to me sufficiently 

 cogent. Should we even learn subsequently that 

 the Paris Axolotl is also derived from a salt lake 

 which is exposed to similar winds to the Lake of 

 Mexico, we still have in this peculiarity of the 

 lakes only a cause tending to make it difficult for 

 the larva to undergo metamorphosis, and to reach 

 a suitable new habitat on the land. The impossi- 

 bility of doing this, or the complete absence of 

 such habitat, does not however follow as a neces- 

 sary consequence, 



It would obviously be a much more solid sup- 

 port for my hypothesis if it were possible to point 

 to some physical conditions of the land which 



1870, p. 149). I may be here permitted to quote a passage 

 from the letter in which Dr. Miiller calls attention to this 

 interesting discovery. "As a proof of the possibility that a 

 reversion form can again become a persistent character in a 

 species or in the allied form of a particular district, I may refer 

 you to an Epidendrum of the island of Santa Catharina. In 

 all Orchids (with the exception of Cypripedittni} only one 

 anther is developed ; in very rare cases well-formed anthers 

 appear as reversions among the aborted lateral anthers of the 

 inner whorl. In the Epidendrum mentioned, these are however 

 always present." 



