604 Studies in the Theory of Descent. 



peculiar conditions for Amphibian life. My 

 esteemed friend Dr. v. Frantzius has called my 

 attention to the fact that this lake as well as many 

 other Mexican lakes is slightly saline. At the 

 time of the conquest of Mexico by Ferdinand 

 Cortez, this circumstance led to the final surrender 

 of the city, as the Spaniards cut off the supply of 

 water to the besieged, and the water of the lake is 

 undrinkable. The ancient Mexicans had laid down 

 water-conduits from the distant mountains, and the 

 city is still supplied with water brought through 

 conduits. 



Now this saltness cannot in itself be the cause 

 of the degeneration to the perennibranchiate form, 

 but it may well be so in combination with other 

 pecularities of the lake. The narrowest part of the 

 lake is the eastern, and it is only in this part that 

 the Axc-lotl lives. Now in winter, violent easterly 

 gales rush down from the mountains and blow 

 continuously, driving the water before them to such 

 an extent that it becomes heaped up in the western 

 portion of the lake, where it frequently causes 

 floods, whilst 2000 feet of the shallow eastern 

 shore are often laid completely dry." 



Now if we consider these two peculiarities, viz. 

 salineness and periodical drying up of a part of the 

 bottom of the lake through continuous gales, we 

 certainly have for the Axolotl, conditions of life 



31 Miihlenpfordt, " Versuch einer getreuen Schilderung der 

 Republik Mejico," Hanover, 1844, vol. ii. p. 252. 



