FISHES. 221 



rapidity. Some are occasionally met with in which the 

 sides are alike in color, most often dark, but sometimes 

 white, and these are said to be " doubles." The fishes 

 of this family differ from all other Vertebrates in a lack 

 of perfect symmetry in relation to the two halves of the 

 body. In all other Vertebrates the two halves are alike, 

 except in some of the internal organs. But in these 

 fishes there is a difference between the two sides in sev- 

 eral particulars. The two eyes are on one side, and are 

 irregularly placed ; in some species they are on the right 

 side, and in others on the left. With this there is an 

 irregularity in the bones of the head, while in all other 

 Vertebrates they are alike on the two sides. Then there 

 is the difference in color. There is also a difference in 

 the pectoral fins, one being longer than the other. 



374. Most of the species of this family belong exclu- 

 sively to the sea, and yet the Flounder and some others 

 occasionally ascend rivers. The Halibut, so well-known 

 in this country, is a very large fish, sometimes six or 

 seven feet long, and weighing four or five hundred 

 pounds. The flesh of the Turbot is considered peculiar- 

 ly fine, and immense quantities are taken in the fisher- 

 ies. Carpenter states that the Dutch receive 80,000 per 

 annum for the supply of this fish to the London market. 



375. The Herring family furnish a great amount of 

 food to man. They are mostly marine fishes ; only a few 

 species, among which is the Shad, ascending the rivers 

 at the spawning season. The common Shad of this coun- 

 try has a much better flavor than the Shad of Europe. 

 The Sardine and Anchovy are aberrant species of this 

 family. The true Herring inhabits the northern seas, 

 and arrives every year in vast legions on the coasts of 

 America, Europe, and Asia, never descending below the 

 45th degree of north latitude. They come to the coast 

 to spawn, and then retire to the depths of the sea, going 

 northward. 



376. The Eels are called Apoda, or Footless Fish, be- 



