CHAPTER II 

 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. Con- 

 trasted with these backboneless animals are the backboned 

 ones, or vertebrates, including the fishes, amphibians, rep- 

 tiles, birds, and mammals or quadrupeds. We shall now 

 examine the external structure of two backboned animals, a 

 fish and a bird. 



The sunfish (fig. 4). 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 Rocky Moun- 

 tains. Where sunfishes cannot be obtained, bass or perch 

 or gold-fish may be used for study. Specimens 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 any neck. How are the scales 

 arranged? Remove a scale and examine it under a hand 

 lens. What sort of an edge has it? Examine the fin, called 

 the dorsal fin, on the back. Note that its front part is com- 

 posed of spines, and its posterior part of soft rays jointed 

 and branched, both spines and rays being connected by and 

 supporting a thin skin. At the end of the tail is the caudal 



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