FROGS AND TOADS— AXOLOTL 413 



curious mode of bringing up its family, the male depositing the eggs laid by the 

 female in a pouch on its throat, where they develop. The pouched frogs, on the 

 other hand, as represented by Nototrema marsapiatum of Mexico and Peru, pass 

 through all the stages of their development in a pouch in the back of the female ; 

 while those of the Surinam water-toad (Pipa americana) develop in the skin of 

 the back of the female, which forms a cell round each egg. 



All the above-mentioned genera, together with many others, such as Phyllodes 

 among the Ranidce and Leptodactylus, Paludicola, and Hylodes among the 

 Cystignathidce (in which group Pseudis is included), are restricted to the South 

 American region. It is, however, noteworthy that Pipa has a near relative in the 

 tropical African Xenopus ; these two genera constituting the family Xenopodidw, 

 or Dactylethridce, which is distinguished from all other batrachians by the absence 

 of the tongue. Two families, namely the Amphignathodontidce, with the species 

 Amphignathodon guentheri of Ecuador, and perhaps the imperfectly known 

 Grypiscus umbrinus of Rio de Janeiro, and the Hemiphractidce, with the genera 

 Hemiphr actus, Ceratophyla, and Amphodus, are peculiar to the present region. 



Some of the strange " nursery " arrangements of South American frogs have 

 been already mentioned ; it may be added that certain tree-frogs of the genus 

 Phyllomedusa (which is another of the types peculiar to the region) spawn in 

 nests of froth made in the leaves of trees overhanging water. The tadpoles hatch 

 in the froth, in which they move freely for a few days till their external gills are 

 shed, when they drop into the water beneath, there to complete their development 

 into frogs. Several kinds of Hylodes, such as the well-known cogni (H. martinensis) 

 of the West Indies, spawn in damp moss or under stones, laying unusually large eggs 

 in which the tadpole undergoes practically its full development, coming forth with 

 a mere rudiment of a tail, which probably served as a breathing organ during its 

 incarceration. Other small South American frogs, pertaining to the genera 

 Dendrobates and Phyllobates, have been observed to go about with their tadpoles 

 adhering to their backs by means of the sucker-like structure of their lips and the 

 flattened surface of the belly. 



A dark-coloured salamander, furnished with external gills, and 

 measuring about ten inches in length, which inhabits the lake 

 surrounding the city of Mexico, is of special interest on account of being the 

 permanently immature form of a species, Arablystoma tigrinum, ranging from 

 New York southwards to California and central Mexico. Normally this species at 

 the close of its aquatic existence develops lungs, sheds its external gills, and takes 

 to a life on land. The axolotl, as its Mexican representative is called, is, however, 

 under normal circumstances aquatic throughout its existence, breeding in this 

 permanently immature condition. Axolotls when kept in confinement will, 

 however, sometimes develop into adult salamanders, which leave the water and 

 take to a life on land after the manner of the rest of their kind. The reason 

 for the arrested development is not definitely known. 



As mentioned in the chapter on the fauna of North America, the salamanders 

 of the genus Amblystoma are mainly characteristic of that continent, where they 

 are represented by about sixteen species. Very interesting is the occurrence of a 

 representative of this otherwise American genus in Siam, as it affords another 



