THE BULLFROG in 



The first of these is more exceptional, in that it has no 

 hind limbs at all, and only a very small pair of fore limbs. 

 This is the Siren, specimens of which have come to the 

 British Museum from various parts of the United States, 

 including South Carolina, Georgia, and Texas. The 

 other American form with persistent gills is named 

 Menobranchus. It is shorter in body, with two pairs of 

 fairly developed limbs. It is a more northern animal, 

 beini? found in Canada as well as the United States. 

 There is a genus of efts, distinguished both from the 

 number and considerable size of the species which com- 

 pose it. It is named Amhly stoma and contains seven- 

 teen different species, all of which are Korth American 



Fig. 30 



THE AMBLYSTOMA. 



(ranging from the northern Rocky Mountains and Van- 

 couver's Island to Mexico), with one exception —a single 

 species which, strange to say, has found its way to the 

 mountains of Siam ! All these species when full grown 

 are quite destitute of gills, though almost all efts (like 

 almost all frogs) pass through a stage of existence in 

 which they do have them. 



There is a soit of eft in Mexico known as the AxolotL 

 which possesses large external gills. It seems a fully 

 adult creature and breeds freely. Long ago, however, 

 the great Cuvier considered that it probably was only 

 an immature animal. 



