XVI. INTRODUCTION. 



together in bodies, but change their movements as may best 

 suit their different modes of attack or defence, in preying 

 upon, or escaping from each other as they pass along.* All 

 these various tribes of fishes, but particularly that of the Her- 

 ring, are in their turns encountered and preyed upon by the 

 whole hosts of sea fowl, which continually watch all their 

 motions. Some are seen to hover over the shoals of fishes, 

 and to wheel about in quick and glancing evolutions, and 

 then to dart down like a falling plummet upon the selected 

 object, which is gliding near the surface of the water, and 

 instantly to rise, and devour the living victim on the wing. 

 Others, equally alert and rapid in their pursuit, plunge and 

 dive after their prey to greater depths; while the less active 

 birds seem content to devour only such of the fishes as have 

 been killed or wounded, and cast out on the flanks, or left 

 in the rear of the main body. 



In this great, this wonderful migration of birds and fishes, 

 it is evident that they are amply provided on their way with 

 an abundance of food, which they derive from each other;: 

 and that the shoals of fishes which the sea-fowl attend, are 

 impelled southward by instinct, aided by currents, for the 

 accomplishment of their mission. The Birds, also, in their 



* " Fishes are the most voracious animals in nature. Many species 

 prey indiscriminately on every thing digestible that comes in their 

 way, and devour not only other species of fishes, but even their 

 own. As a counterbalance to this voracity, they are amazingly pro 

 lific. Some bring forth their young alive; others produce eggs. The 

 viviparous Blenny brings forth 200 or 300 live fishes at a time. Those 

 which produce eggs are all much more prolific, and seem to propor- 

 tion their stock to the danger of consumption. Lewenhock affirms 

 that the Cod spawns above nine millions in a season. The Flounder 

 produces above one million, and the Mackarel above 500,000. 

 Scarcely one in a hundred of these eggs, however, is supposed to 

 come to maturity: but two wise purposes are answered by this 

 amazing increase; it preserves the species in the midst of numberless 

 enemies, and serves to furnish the rest with a sustenance adapted to 

 their nature." Encvcl. Britan. 



