FISHES. 233 



fined to spawning, or to feeding upon some particular 

 bait or both; among these, the gadoid (codfish) 

 and clupeoid (herring) famihes advance from polar 

 and temperate latitudes towards the equatorial seas, 

 while the mugiloed (mullets) and scomberoid (mack- 

 erels) take a contrary direction, from the warm lati- 

 tudes towards temperate seas. But all the fish of 

 passage, though some feed on mollusca at greater 

 depths are necessitated to deposit their spawn from 

 soundings of at most forty fathoms to the superfi- 

 cial sands and rocks within the tides. Thus far we 

 may judge the sun's rays to penetrate with effect, 

 not only from the quickening of their eggs, but 

 also from the same action upon those of all the other 

 species of fish, and of the pullulations of the subor- 

 dinate classes of animated beings, excepting, per- 

 haps, the zoophytes of some tropical regions, which 

 ■ commence their calcareous dwellings under a verti- 

 cal sun at greater depths and those pelagian animals 

 whose spawn floats on the surface,*" while the mi- 

 gratory tribes deposit upon the zone of soundings 

 just mentioned the germs of their own future brood, 

 to be in part devoured by other species, they find 

 in their turn the ova and the fry of those species, 

 and also the already -matured new generations of 

 the subordinate classes, to serve for their own 

 subsistance. 



Pelagian fish, though many species are gregari- 

 ous, are not so clearly migratory as the foregoing, 

 they, as the name imports, are residents in the high 

 seas, and among them the Scomberodi family 

 (mackerels), and particularly the genera Istiophorus, 

 (Indian sword-fish), Xiphias (Atlantic sword-fish), 



* It raay be necessary to qualify this observation by remarking 

 that in warmer seas, and particularly in tropical waters, some of 

 the sedentary species may spawn several fathoms below forty, 

 perhaps even as far down as sixty fathoms. Yet almost all the 

 tropical percoids deposit their ova about the coral rocks, much 

 nearer the surface, and the Spari, Scari, and Labri do not descend 

 lower. 



VOL. V. IBS"). iV 



