AMPHIBIA 189 



which are nearly definitive in form. Spelerpes hilineatus, another 

 newt of the Atlantic States, has been described by H. H. Wilder. 

 It is about four inches in length, brownish yellow in color above, 

 with a black lateral line, and brightest yellow beneath. It lives 

 a nocturnal life and hides under stones or logs. The eggs are 

 laid in bunches of thirty to fifty on the under sides of submerged 

 stones. S. fuscus (Fig. Ill) has an extremely extensible tongue, capa- 

 ble of being shot out nearly two inches. With this it captures in- 

 sects by means of a sticky disk on its end. 



Amblystoma tigrinum (Fig. 112, A) the "tiger salamander" is the 

 commonest and most widely distributed of North American salaman- 

 ders. It occurs from the Atlantic Ocean to Minnesota and well into 

 the Southern States. The ground color is nearly black, with large yel- 

 low spots and blotches, which sometimes merge into broad stripes or 

 bands. It lives in damp situations on land, under stones or logs, and 

 is not infrequently found in cellars. The large prominent golden 

 eyes, the very broad head and large mouth, are characteristic features. 

 The length varies from five to nine inches. This species is best known 

 because of the fact that it exhibits a classic case of pcedogenesis or neo- 

 teny, the capacity to become sexually mature while still retaining the 

 larval body. The larva of Amblystoma is the classic Axolotl (Fig. 112, 

 B), which has for a long time been abundant in the lakes near Mexico 

 City. It was supposed to be a perennibranchiate species and was 

 called "Siredon axolotl." The true situation, however, was revealed 

 when some of these larvse were kept in aquaria in Paris. Some of 

 them lost their gills and other aquatic adaptations and metamorphosed 

 into the well-known Amblystoma tigrinum, a purely terrestrial type. 

 It was found possible by experimental means to control the metamor- 

 phosis so as to keep the animals permanently as Axolotls, or to cause 

 them to metamorphose promptly into adult Amblystomas. Even 

 after metamorphosis had begun it was possible to check it and cause 

 the animals to revert to the Axolotl condition. This situation throws 

 fight on the significance of some of the perennibranchiate species 

 that never metamorphose; for it has often been suggested that these 

 forms are permanent larvse or that they exhibit a type of racial 

 psedogenesis that has become so fixed that metamorphosis is no 

 longer possible. 



Salamandra maculosa, the "spotted" or "fire salamander" is one 

 of the commonest salamanders of Europe, having a wide range over 



