FISH IN GENERAL. 39 



their congeners, have partial migrations to the deep soundings 

 of the west coast of Africa, into the Mediterranean and the 

 China seas. Similar kinds of travels are undertaken by some of 

 the exoceti ; but doradoes or coiyphamaj, the greater species of 

 squali and cephalopteri, come in shore from accidental causes 

 only, or in pursuit of the migratory armies. There is, however, 

 no reason to believe, that in all their wanderings, any of these 

 species are ever induced to descend to very great depths for 

 a considerable time ; but finding their food principally near 

 or on the surface of the sea, they constantly remain near it, 

 and may be seen occasionally hunting their prey even in the 

 night. The naucrates and parasitical echeneis attend the 

 greater cartilaginous genera, but it may be doubted whether 

 other acanthopterygian tribes besides those already men- 

 tioned are strictly pelagian, and venture in the high seas 

 many degrees from soundings. There are, it is true, several 

 percoides, such as polyprion, and other genera, whose species 

 are common to the shores of both hemispheres, and pass i-ound 

 Africa even into the Red Sea, and eastward perhaps beyond 

 the coasts of Ceylon ; but in the latter case they are probably 

 coasters, and in the former they make their passage across 

 the Atlantic by attending the sea-weed. 



It would be certainly assuming too much, to assert that, 

 the truly pelagian fish excepted, no other species cross the 

 ocean without the aid of those aquatic plants known by the 

 vulgar name of the gulf weed, and among which the fucus 

 natans, L. is probably the most conspicuous ; but certain it 

 is, that numerous gelatinous animals, small mollusca, scyllaea, 

 and pelagic crabs, and the fry of different species of fish, 

 harbour in this weed wherever it is taken up and examined. 

 In steering towards the equator, it is usually first observed in 

 fields and islands on the surface of the sea south of Madeira, 

 and if we take this place for a point of departure, the trade 



