The class Amphibia is distinguished by no such simple earmark as the hair of mammals, or the feathers of birds. For the most part amphibians have a naked skin, the young respire by means of gills and differ in body form from the adult. There are exceptions the this characterization, for there are salamanders such as Necturus which retain the larval gills throughout life, and there are fossil amphibia, the Stegocephalia, as well as the living tropical Apoda, which have scales or plates in the skin. The red blood corpuscles are nucleated, biconvex and oval. Gills are present, at least during some early stages of development.
Development takes place without amnion and allantois.
Fins, when present, lack the supporting rays characteristic of fishes. Examine the frog skull and note the number of condyles. Study the microscope slide showing corpuscles of frog s blood. Compare specimens of a lizard and a salamander and be certain that you can tell an amphibian from a reptile. Relation of Class Amphibia to other groups of animals.