TAILED BATRACHIANS 261 



thirdly, that no change takes place when the creature is 

 placed in water from which the necessary oxygen has been 

 eliminated, showing that the quantity of oxygen in the 

 lakes of Mexico can have little bearing on the phenomenon. 

 The shrinking gills and fins, I found, could be made to 

 undergo fresh development in the early stages of the 

 metamorphosis, by replacing the animals into deep water 

 after they had been forced to breathe air, when the 

 previous stages in the development were resumed in just 

 half the time required to reach them. 



The Axolotl breeds freely in captivity, the eggs, about 

 100 in number, laid in the early winter or spring, being 

 attached in bunches of about half a dozen to aquatic 

 plants. The animals can almost invariably be made to 

 breed by keeping them in small tanks without any plants, 

 and then suddenly transferring them to large aquaria well 

 supplied with vegetation. The eggs are hatched in from 

 ten to twenty days, according to the temperature of the 

 water. The larvae, which at first should be given Daphnia, 

 and later worms, grow rapidly, and are sexually mature 

 when about a year old. 



It is a peculiar fact that the fingers and toes of regener- 

 ated limbs are often webbed instead of being free, as in 

 normal specimens, and consequently the ancestral Ambly- 

 stome is believed to have had webbed feet. 



A. altamirani, which lives close to the haunts of A. 

 tigrinum, in the mountain streams, up to an altitude of 

 10,000 feet, is yellow and black, like the latter species, 

 when half grown, but when fully adult becomes grey, with 

 black spots. This species, although transforming when 

 only five months old, is essentially aquatic. Dr. Gadow 



