FISHES. 345 



nsus in the Ammnitates AcademiccB, vol. i. It is a very 



small species, native to Senegal and some other parts of 

 Africa. 



The great and almost inexhaustible class of fishes next 

 demands our attention. 



Our acquaintance with the laws which regulate the geo- 

 graphical distribution of this class is extremely meager : in 

 other words, the facts illustrating the greater or less ex- 

 tension of their localities are few, and have never been 

 properly generalized. From the immeasurable extent and 

 continuous nature of the fluid which they inhabit, they are 

 supplied by nature with greater facilities of dispersion than 

 most other animals ; while the greater equality of the 

 temperature of water, when compared with that of either 

 earth or air, admits, in several instances, of the same spe- 

 cies inhabiting almost every latitude from pole to pole. 

 Those races especially, which, travelling together in vast 

 shoals, speedily consume the natural food which each par- 

 ticular spot affords, are obliged, like the pastoral tribes of 

 old, or the woodland hunters of America, to remove from 

 place to place in search of additional supplies, and thus the 

 species acquires a more widely extended geographical dis- 

 tribution. It is thus that the cod and herring are spread 

 over the whole extent of the Northern Ocean, and in undi- 

 minished numbers, notwithstanding the war of extermina- 

 tion which man and other voracious animals appear to 

 wage against them. Those species which lead a solitary 

 and, as it may be called, a stationary life are frequently 

 confined within very narrow limits. The Chaiodons, for 

 example, which delight in rocky coasts covered with madre- 

 pores, attach themselves to the torrid zone, which produces 

 so abundantly those magnificent ornaments of the sea. 

 But though thus confined to particular spots, from which 

 the individuals of the species never wander, the species 

 itself may be said to be repeated again in different and 

 distant regions, separated from each other by almost in- 

 surmountable obstacles. Thus, many of what may be 

 termed stationary species are found identically the same 

 along the coasts of Brazil, in the Arabian Gulf, and over 

 the multiplied shores of Polynesia. It has hence been 

 concluded that such species, incapable of colonizing them 



