THE SALAMANDER TRIBE 2669 



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 ex- 

 amples 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 fol- 

 lowing 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. ' Toward the end of the same month, and in the early part of October, 

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

 the 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 immediatel}' 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 de- 

 veloped 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 transformations; but that, 

 owing to the dry nature of the country it inhabits, it has acquired the habit of re- 

 taining the larval condition permanently. From its being able to breed in this state, 

 it may further be inferred that the tadpole stage was originally the permanent con- 

 dition of all members of the order, and that the salamander stage is a later devel- 

 opment. 



There are six other genera, belonging to the subfamily Ambly stoma- 

 tinte, of which Hynobius is represented by several Japanese species. 

 Salamandrella, distinguished by having only four hind-toes, is a Siberian type, 

 with two species; Onychodadylus, which may be recognized by its black claws, is 

 known by one species from Japan; while Ranidens, from Eastern Siberia and North- 

 eastern China, Batrachyperus from Moupin in Tibet, and the Californian Dicampto- 

 don, all of which have the palatal teeth arranged in two arches, with their convexity 

 forward, and separated by a wide space in the middle, are likewise respectively rep- 

 resented by a single species. The two remaining subfamilies, which are exclusively 

 American, can receive only very brief notice. In the first of these (PUthodontina) 

 the series of palatal teeth is transverse and situated on the hinder part of the vo- 

 mers; while there are also teeth on the parasphenoid bone; the bodies of the verte- 

 brae being cupped at both ends. Of the five genera, Plethodon, with the tongue 

 attached along the middle line to the anterior margin, and five hind-toes, is North 

 American, where it is represented by several species. On the other hand, the large 

 genus Spelerpes, which has the tongue attached only by a central pedicle, and all its 

 edges free, ranges into Central America and the West Indies. The fourth sub- 

 family, Desmognathintz, differing from the last by the bodies of the vertebrae being 

 cupped behind and convex in front, is represented by Desmognathus from North 

 America generally, and Thorius with one Mexican species. 



