CHAPTER V 

 THE SUNFISH AND THE SPARROW 



The two animals whose external structure we have 

 studied are both backboneless or invertebrate animals. 

 Most of the smaller animals are without internal bony 

 skeletons and hence without backbones. This is true of 

 the sponges and sea-anemones, the starfishes, the worms, 

 the crayfishes, crabs and lobsters, the centipedes, and the 

 spiders, as well as of the insects and the snails, slugs, 

 and clams. Contrasted with these backboneless animals 

 are the backboned ones, or vertebrates, including the 

 fishes, amphibians, reptiles, birds, and mammals or 

 quadrupeds. We shall now examine the e.xternal struc- 

 ture of two backboned animals, a fish and a bird. 



The sunfish (fig. 31). — Some kind of sunfish can be 

 found in the streams of any part of the United States, 

 except in Washington and Oregon, and in the higher 

 Rock}' Mountains. Where sunfishes cannot be obtained, 

 bass or perch or gold-fi.sh may be used for study. Speci- 

 mens should be taken alive if possible, and kept in a 

 large jar or tub of fresh water. 



Examine a live sunfish. Note the deep, flattened trunk 

 of the body, and the paddle-like tail. The head is 

 closely fitted to the trunk without anj^ neck. How are 

 the scales arranged? Remove a scale and examine it 

 under a hand lens. What sort of an edge has it? Ex- 

 amine the fin, called the dorsal fin, on the back. Note 

 that its front part is composctl of spines, and its posterior 



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