CHAPTER XLII 

 THE ORDER OF TAILED AMPHIBIANS 



URODELA 



The members of this Order are readily dis- 

 tinguished from the preceding group by the pos- 

 session of tails, which they retain throughout 

 their lives; by their gills, which most of them 

 retain permanently; by the absence of scales, 

 and by the fact that with very few exceptions 

 they are strictly aquatic. It is safe to say that 

 any four-legged aquatic creature having a tail 

 but no scales, is either a salamander, newt, mud- 

 puppy or siren. 



The Order U-ro-de'-Ia is the dividing line 

 between the finny, gill-breathing fishes, and the 

 four-legged, lung-breathing, land-going lizards. 

 Strange to say, its members are most abundant 

 in the temperate regions of the earth, and except 

 in two or three small areas, are absent from the 

 tropics. In Australasia there are none, and in 

 South America and Africa there are none save in 

 their extreme northern portions. 



Of all countries, the region embracing the 

 United States and the southern provinces of 

 Canada is by far the richest in species belonging 

 to this Order, the total number present being 

 fifty-two. Mexico and Central America con- 

 tribute fourteen more, all salamanders. In 

 this total of sixty-six species, eighteen genera 

 are represented, fourteen of which are found 

 only in the New World. The total number of 

 species in the Old World is only thirty-six. In 

 North America, the northern boundary of the 

 Order Urodela is a line extending due east and 

 west across the continent about on the 52d 

 parallel of latitude. ("Amphibia and Reptiles," 

 Dr. Hans Gadow, pp. 95-6.) 



THE FAMILY OF SALAMANDERS. 



Salamandridae. 

 The members of this Family seem to be en- 

 gaged in a continuous struggle at the dividing 

 line between lungs and gills, and exhibit all pos- 



sible variations between perfection in both those 

 organs. One species (the axolotl) changes from 

 water to land with neatness and despatch. 

 Another (the striped - backed salamander) lin- 

 gers for two or three years in its larval state, in 

 the water, while the blue-spotted salamander 

 lives upon land, in moist forests. But one or 

 two illustrations must suffice for all. 



The Axolotl, 1 of Mexico, is in some respects 

 the most striking — even theatrical — example 

 of salamandrine life and character. Its trans- 

 formation is so rapid and complete that it is 

 highly impressive. As an Axolotl, it is either a 

 dark gray or a perfectly white and almost trans- 

 lucent animal, about 7 inches long, with external 

 gills divided into three long, ragged branches; a 

 long tail with a continuous fin above and below, 

 and four very practical legs. This is the larva. 



If the pond in which this creature lives threat- 

 ens to dry up, the gills and the fins on the tail and 

 back begin to shrink, and disappear, and the ani- 

 mal begins to breathe air at the surface of the 

 water. Finally, when the transformation is 

 complete, a lizard-like animal with very ser- 

 viceable lungs, no gills whatever, and not a ves- 

 tige of fins on tail or back, emerges upon the land, 

 and thereafter leads a terrestrial life. It is then 

 known as a Spotted Salamander; and it is no 

 wonder that for many years these two forms were 

 considered creatures of different species. It was 

 in the Jardin des Plantes, in Paris, that the 

 process of birth, growth and transformation was 

 finally discovered. 



It is not difficult to bring about the transfor- 

 mation of the Axolotl, by gradually diminishing 

 the water-supply, and thus observing from day to 

 day the progress of the change. More than this, 

 the transformation can be arrested by gradually 

 diminishing the allowance of air, thus forcing the 

 1 Am-bly'sto-ma ma-vor'ti-um: 



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