648 



COMPARATIVE ANATOMY 



lina to Mississippi in our Southeastern States. This is known as Am- 

 phiuma means, and is eel-shaped with much reduced limbs and a small 

 pair of inconspicuous gill-clefts guarded by skin-flaps. Some of these 

 animals are three feet in length, living in swamps and muddy water. 

 The female protects the eggs by coiling about them. 

 Family II. Salamandridae. (Salamanders and Newts) (Fig. 374). 



These animals have no gills in the adult stage. Practically three- 

 fourths of all tailed amphibia belong to this family. 



The most common type is the Desmognathus fuscus (Fig. 374). 

 The female coils about the eggs when laid. The young, after hatching, 

 look quite like adult forms. 



Amblystoma tigrinum or "tiger salamander" (Fig. 374) is very com- 

 mon in North America. It has large yellow spots which may merge 

 into broad stripes or bands. The ground color is black. It may be 



Fig. 374. Salamandridae. 



In C, I, Female; 2, Male at the breeding season with well-developed frills. 

 E, Desmognathus fuscus (American newt). Female with eggs in underground hole. 

 (A, after Holder ; B, from Cambridge Natural History ; C, after Gadow, E, after 

 Wilder.) 



found in damp places under stones and logs, or even in cellars of houses. 

 It is one of the classic forms used in the laboratory for various reasons, 

 one of them being that it is an animal which becomes sexually mature 

 while still in the larval stage, a condition called paedogenesis or neoteny. 

 Another very interesting fact is brought out in the life of the larval 

 forms of Amblystoma. The larva itself is called Axolotl, and was for- 

 merly considered to be a fully adult form. It is quite common near 

 Mexico City. However, when some of the Axolotls were taken to 

 Paris, and kept in aquaria, they metamorphosed into regular, full-fledged 



