AXOLOTLS. 



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they are larval forms. However, in the Mexican lakes, the axolotls remain 

 permanently in the water, retaining their gills throughout life, and laying eggs, 

 as if they were adult ; and it was consequently long considered that they belonged 

 to a type with persistent gills. It was not, indeed, until the year 1865, that light 

 was thrown on the history of these remarkable creatures by six examples which 

 had been living for more than a year at Paris. These comprised five males and 

 one female, and in the middle of February the latter began to lay eggs, which in 

 the course of a month hatched into tadpoles like their parents. In the following 

 September the gills and crest of the tail of one of these began to shrivel, while the 

 head increased in size, and yellow spots made their appearance upon the dark skin. 

 Towards the end of the same month, and in the early part of October, similar 

 changes took place in the others, and soon afterwards the whole four assumed the 



ADULT OK MEXICAN AXOLOTL {\ nat. size). 



appearance of the salamander, which had been previously described as Ambly stoma 

 tigrinum. Subsequently experiments were made with other young axolotls by 

 placing them in a glass vessel filled with water, but with rocks at one end, so that 

 the creatures could creep out and expose themselves to the air as much as they 

 pleased. After a day's interval the amount of water in the vessel was diminished ; 

 and almost immediately the gills of the axolotls began to shrink, and in the course 

 of time, during which they dwelt chiefly in damp moss, the creatures gradually 

 developed into air-breathing salamanders. It has been inferred from these 

 remarkable experiments that the Mexican axolotl, like the other members of the 

 genus to which it belongs, originally went through the normal series of trans- 

 formations ; but that, owing to the dry nature of the country it inhabits, it has 

 acquired the habit of retaining the larval condition permanently. From its being 

 able to breed in this state, it may further be inferred that the tadpole stage was 



