Pisces. 171 



2. The gills are protected by a gill cover, so that there 

 is but one external opening. 



3. The eggs are small and numerous. 



The Spiny-rayed Fishes. The perch is typical of a 

 large group of fishes, all of which have spiny rays. The 

 perch is widely distributed in fresh-water lakes and streams ; 

 the sea perch, or cunner, is common along the Atlantic 

 coast, and is so nearly like the yellow or " ringed " perch 

 that the descriptions and directions for dissection will apply 

 fairly well to it. 



In the same family with the perch is the pike perch, 

 better known as the " wall-eye" or wall-eyed pike, an 

 excellent food fish. Among the perches are also the 

 darters, a most interesting family on account of their small 

 size and peculiar habits. 'They rest on the bottom, never 

 poising in the water like ordinary fishes ; they are found 

 in streams, in rapid currents, getting their food under 



106. MACKEREL. 



stones, etc. They swim by means of their pectoral fins, 

 coming to rest after the quick, darting motion that gives 

 them their name. One species is only from an inch to an 

 inch and a half long. Yet in some respects they are to be 

 classed among the most highly developed of fishes. They 

 may be caught in a minnow seine by taking pains to " keep 

 the lead line down," that is, by being careful to drag very 



