XVI. THE FISH AND FROG, AN INTRODUCTORY 

 STUDY OF VERTEBRATES 



Problems, — To determine how a fish and a frog are fitted 

 for the life they lead. 



To determine some methods of development in vertebrate 

 animals. 



{a) Fishes. 



Q)) Frogs. 



(c) Other aniinals. 



Laboratory Suggestions 



Laboratory exercise. — Study of a living fish — adaptations for pro- 

 tection, locomotion, food getting, etc. 



Laboratory demonstration. — The development of the fish or frog Oi^g. 



Visit to the aquarium. — Study of adaptations, economic uses of fishes, 

 artificial propagation of fishes. 



Two Methods of Breathing in Vertebrates. — Vertebrate 

 animals have at least two methods of getting their oxygen. In 

 other respects their life processes are nearly similar. Of all 

 vertebrates fishes are the only ones fitted to breathe all their lives 

 under water. Other vertebrates are provided with lungs and 

 take their oxygen directly from the air.^ We will next take up 

 the study of a fish to see how it is fitted for its life in the water. 



STUDY OF A FISH 



The Body. — One of our common fresh-water fish is the bream, 

 or golden shiner. The body of the bream runs insensibly into the 

 head, the neck being absent. The long, narrow body with its 

 smooth surface fits the fish admirably for its life in the water. 

 Certain cells in the skin secrete mucus or slime, another adapta- 



1 With the exception of a few lungless salamanders. Most salamanders get nQiicb 

 of their supply of oxygen through their moist skins- 



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