CHAPTER XXVHI 



THE AMPHIBIA 

 THE FROG AND ITS RELATIVES 



Vocabulary 



Transition, period of change. 

 Vegetarian, using vegetable food. 

 Carnivorous, using animal food. 

 Constitute, to make up or compose. 

 Pulmonary, pertaining to the lungs. 

 Aerated, supplied with air. 

 Viscera, all the internal body organs. 



Particular interest attaches to this group because of the fact 

 that, in their life history, we can see the steps in development 

 between the fishlike animals adapted solely for aquatic life and 

 the land animals which cannot live under water. 



In this transition from water to land forms, many strange 

 combinations of gills and lungs, fins and legs, have occurred, 

 gills being found on animals with legs, and fins sometimes ac- 

 companied by lungs. All together this is a very good object 

 lesson in the development and adaptations of animal forms. 



The name amphibia, meaning " having two lives," refers to 

 the fact, that they usually are aquatic, fishlike animals when 

 young, and abandon that manner of life for the land when they 

 become adults. This series of changes is called a metamorphosis, 

 just as was the life history of some insects. 



Characteristics. The characteristics of the group may be 

 summarized as follows, though there are some exceptions: 



1. They undergo a metamorphosis. 



2. Eggs are directly fertilized as laid. 



3. Usually they are covered by a smooth skin. 



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