ZOOLOGY. 



161 



jiished with JSiditating Memhrmies^ by \vl;ich their eyes are 

 secured from extfcrnai injury, to which tliey are particularly 

 subject Irom fhe velocity of their motioriS ; not fhat we con- 

 sider tiieij' int tious conipciral .ly speak' : g,, so rapid as those 

 of ma.jy ii.iadi of birds ; as a fish '."iien swimming, needs but 

 littld exertion io ropel it forward, it , specific gravity being 

 so near thi t of the eiement in which it moves ; whereas, ia 

 the flight of a bird, whosfi specihc gravity greatly exceeds 

 thatc l ai , « very considerable expenditure of exertion is 

 necer s?^y. merely to sustain it in air^ without assisting tp 

 impel them forward. 



Most of this class are exceedingly voracious ; they feed on 

 the lesser kii»ds offish, moluscas, aquatic insects, worms, sea 

 weed, and on most kinds of rlpad carcasses : they are used as 

 food by Man, the larger k'*nds of birds of prey, the 

 Aquatic Mammaliae, and Amphibese. Their increase is asto- 

 nishingly great, most species are oviparous^ but a few produce 

 their young alive. 



The migration of Fishes has attracted the attention of 

 Mankind from the earliest ages, and like that of Birds, is 

 attributable to the want of proper places, wherein to deposit 

 their eggs or spawn, or to a dearth of food. Those that spawn 

 early in the year, generally deposit their eggs iu shallow 

 waters, where the rays of the sun call them into life; 

 these, as they advance in age, soon quit the shallows, and 

 finally abandon the shore for the season. The difficultie? 

 j'lvcrcome by various species, when seeking out a place 



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