136 ORIGIN OF LIFE IN AMERICA 



depend upon the testimony based on the remarkably discon- 

 tinuous ranges of the two recent species. Any theory as to 

 the home of the giant salamanders should be founded on that 

 of other animals possessing a similar range. 



The hellbender is not the only large amphibian frequent- 

 ing tihe rivers of the eastern States. A somewhat eel -like 

 creature, with feeble diminutive limbs and three pairs of 

 bushy external gills, inhabits many of the larger streams 

 and lakes in the north-eastern States.* It grows to about the 

 same length as the giant salamander, but belongs to quite a 

 different family. It is commonly known as the " Mud puppy " 

 (Necturus maculatus), and does not occur west of the Rocky 

 Mountains. Now in this case the nearest relation of the east 

 American form does not live in Eastern Asia, but, like that 

 of the mud minnow (see p. 51), in Eastern Europe. This 

 European member of the family Proteidae has manifestly 

 undergone a certain amount of degeneration. It possesses 

 only three fingers and two toes, is completely blind, and is 

 restricted to the subterranean waters of Dalmatia and the 

 neighbouring provinces of southern Austria. The ''Olm" 

 (Proteus anguineus), as it is called, is scarcely a foot long, 

 and quite white except for the gill bunches which are 

 brilliantly red in colour. It was believed that the Texas 

 subterranean newt (Typhlomolge rathbuni) was related to 

 the mud puppy. Miss Emerson,f however, has shown that 

 it is a salamandrid. No fossil remains of any of these amphi- 

 bians are known, and any theories as to the origin of the 

 discontinuous distribution of the members of this ancient 

 family, must be based on zoogeographical data. 



The family of true salamanders and newts (Salamandridae) 

 likewise comprises certain members which seem to be of 

 very ancient origin, such as the blunt-nosed salamanders 

 (Amblystoma). Being only semi-aquatic animals, they 

 possess greater facilities for dispersal than the purely fresh- 

 water forms. Most of them are large species, the tiger sala- 

 mander (Amblystoma tigrinum) growing to nearly a foot in 

 length, and they only repair to the water in the spring to 



* Cope, E. D., " Batrachia of North America," p. 26. 

 + Emerson, E. T., "Anatomy of Typhlomolge," p. 72. 



