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O F F I S H E S. 



IT has been thought that all fifh are naturally of the ocean; and that 

 fome have mounted into frefh water by accidental migration; yet, a^ 

 many cannot live in fait water, this is at lead doubtful. A few, indeed, 

 fwim up rivers to depofit their fpawn ; but the great body of fifhcs keep to 

 the fea, and would quickly expire in frelh water. 



The number of filh which we have named, and whofe figure we 

 know, according to Linnseus, is above four hundred. But of the greateft 

 part of thefe we know very little befides their figure. Thofe qualities, 

 Angularities, or advantages, that render animals worth our attention, are 

 undifcovered. The hiftory of fiihes, therefore, has little in it entertain- 

 ing: and will detain us proportionably lefs than any fubjeft yet intro- 

 duced. 



Moll filh offer the fame external form, fharp at either end, and fuell- 

 ing in the middle, by which they are enabled to traverfe the fluid which 

 they inhabit, with greater celerity and eafe. Every part feems exerted in 

 this difpatch ; the fins, the tail, and the activity of the whole back- bone j 

 and to this flexibility fiflies owe their great velocity. The fins aflift not 

 only in progreffion, but in rifing, finking, turning, or even leaping out of 

 the water. The pecJoral ^ns^ like oars, pufli the animal forward ; they 

 are placed behind the opening of the gills; generally large and fl;rong; 

 and are to fifli in the water what wings are to birds in the air. They 

 alfo balance the ftfli's head, when large, and keep it from tumbling 

 prone to the bottom ; as is fecn in large-headed fiflies, when the pedoral 

 fins are cut off. Next thefe are the ventral fins, toward the lower part of 

 the body, under the belly : thefe always lie flat on the water; and ferve 

 to raife or deprefs the fifti. The dorfal fin is fituated along the ridge of 

 the back j keeps it in equilibrio, and alfo affifts progreffive motion : In 

 many this is wanting j but in all flat fiflies it is very large, as thepefloral 

 fins are proportionably fmall. The anal fin lies between the anus and the 

 tail ; and ferves to keep the fifli upright. But the tail, which in fome is 

 flat, in others upright, feems the grand inftrument of motion : the fin? 

 are fubfervient to it, and dire<5t its impetus. 



To explain this by experiment — A carp put into a large veflel, in a fl:ate 

 of repofe, fpreads all its fins, and feems to teflon its peroral and ventral fins 

 near the^ bottom. If the filh folds up either of its peroral fins, it incjines to 



Part V. No. 29, Mm thai 



