PRELIMINARY CONSIDERATIONS. 
In order to make clear the positions which the two groups 
under consideration hold in the animal scale, the following brief 
scheme of classification is given : 
Sub-Phylum VERTEBRATA.—Animals with cartilaginous or 
osseous spinal column. 
Class CycLosTOMATA.—The Hag-fishes and Lampreys. 
Class Pisces.—The Fishes. 
Class BATRACHIA.—Skin' naked, not provided with scales. 
Class REPTILIA.—Skin covered with scales. 
Class AvES.—The Birds. 
Class MAMMALIA.—Those that suckle their young, as e. g., the 
horse, dog, man. 
From the above it will be seen that the living Batrachians 
differ from the Reptiles by the former having a smooth skin, with- 
out scales, while the reptiles have scales covering the body. The 
early stages of Batrachia are spent in the water. The eggs are 
laid there and develop into tailed larvae, commonly called ‘ tad- 
poles,’’ which swim about for a certain period, breathing by 
means of gills. Later, in the majority of species, the larvae 
emetge from the water and assume a terrestrial mode of life, 
breathing by means of lungs. The lower forms, however, such 
as the salamander, require moisture, their lungs being poorly 
developed, and one or two groups never leave the water, but 
remain in their lowly condition, breathing by means of gills 
throughout their lifetime. The higher forms, stich as the toads 
and frogs, on leaving the water, lose their tails and develop long 
and strong hind legs for leaping. 
Passing to the Reptiles we have such diverse kinds of organ- 
isms as the lizards, with four legs; the snakes, which have 
lost their legs, and the turtles, which have acquired a hard cover- 
ing, the shell, to protect their bodies. 
Very frequently salamanders are taken by the uninitiated to 
belong tothe lizard group. From the considerations given above, 
it is evident what the differences are and no confusion should be 
: 1. In the fossil Batrachia, to be spoken of later, the skin is covered with heavy bony 
“plates. 
