166 ANIMAL FORMS 



seaweed, the male carrying the eggs about in his pocket 

 until they hatch ; the mullet, stupid, blundering, feeding 

 on minute plants, crushing them in a gizzard like that of 

 a hen, but withal having soft flesh, good for the table ; the 

 flying-fishes, which sail through the air with great swiftness 

 to escape their enemies. 



161. The spiny-rayed fishes. In the group of spiny- 

 rayed fishes the ventral fins are brought forward and joined 

 to the shoulder-girdle. The scales are generally rough to 

 the touch, and the head is usually roughened also. There 

 are many in every sea, ranging in size from the Everglade 

 perch of Florida, an inch long, to the swordfish, which is 

 thirty. These are the most specialized, the most fish-like 

 of all the fishes. Leading families are the perch, in the 

 fresh waters, the common yellow perch, familiar to all boys 

 in the Northeastern States ; the darters, which are dwarf 

 perches, beautifully colored and gracefully formed, living 

 on the bottoms of swift rivers ; the sunfishes, with broad 

 bodies and shining scales, thriving and nest-building in 

 the quiet eddies ; the sea-bass of many kinds, all valued for 

 the table ; the mackerel tribe, mostly swimming in great 

 schools from shore to shore. After these come the multi- 

 tude of snappers, grunts, weakfishes, bluefishes, rose-fishes, 

 valued as food. Then follow the gurnards, with bony 

 heads; the sculpins, with heads armed with thorns, the 

 small ones in the rivers most destructive to the eggs of 

 trout ; and at the end of the long series a few families in 

 which the spines once developed are lost again, and the 

 fins have only soft and jointed rays. It is a curious law of 

 development that when a structure is once highly special- 

 ized it may lose its usefulness, at which point degeneration 

 at once sets in. Among fishes of this type are the cod- 

 fishes, with spindle-shaped bodies, and the flounders, with 

 flat bodies. The flounders lie on the sand with one side 

 down, and the head is so twisted that the eyes come out to- 

 gether on the side that lies uppermost. This side is col- 



