8 FARM ANIMALS 
are the Amphibia, a class of animals that includes, among 
others, the toads, frogs and salamanders. In amphibia, the 
DEVELOPMENT OF A TOAD IN A 
SINGLE SEASON 
body, except in the toads and 
frogs, is fishlike, though limbs 
.and Jungs are present. Toads 
and frogs undergo a metamor- 
phosis; the young, called tad- 
poles, breathing by external 
gills, and at first being without 
legs. They are adapted both 
to water and land life. Tishes, 
you know, are water dwellers, 
breathing by gills; while rep- 
tiles, birds and mammais are 
air breathers, never possessing 
gills, except for a short time 
during the embryo stage. 
Toads and _ frogs, even 
though adapted to water, are 
obliged to come to the surface 
to breathe. 
13. Reptiles—These occupy 
the place between the amphib- 
ians and the birds. They are 
cold-blooded and breathe by 
lungs. They include serpents, 
lizards, tortoises and croco- 
diles. With the exception of 
tortoises, the reptiles are elon- 
gated in form, the body cylin- 
drical, which usually termi- 
nates in a long tail. Limbs are 
not found in serpents or in some of the lizards. In other 
