<;ENLRAL DESCRIPTJON OF FISHES. S 



with the pectoral fin effectually produces it: if 

 the fish desires to turn either way, a single blow 

 with the tail the opposite way sends it round at 

 once: it' the tail strike both ways, the motion 

 produced by the double lash is progressive, and 

 enables the fish to dart trowards with an astonish- 

 ing velocity. The result is not only in some 

 cases, the most rapid, but in ail cases the most 

 gentle^ pliant, easy, animal motion^ with which 

 we are acquainted. However, when the tnil is 

 cut off, the fish loses all motion, and gives itself 

 up where the water impels it. 



Fishes are distmguisiied into sea, or salt w^ater 

 fish, pisces marini'y as the whale, herring, macka- 

 reJ, &c. river or fresh water fish, piscesjiuviales: 

 as the pike, trout, S;c. and pond or lake fish : as 

 the carp, tench^ 8cc. to which may be added, 

 others which abide indifferently in fresh water, 

 or salt, as salmon, shad-fish, 8cc. 



There are also an amphibious kind, which live 

 indifferently on land or water: as the castor, ot- 

 ter, &c. 



Aristotle, and after him Mr. Willoughby, more 

 accurately distinguish yif"s//e,s into cetaceous, car- 

 ti/iganous and sp2/ious. 



The cetaceous kind, called also hellucc mariiKE, 

 have lungs, and breathe like quadrupeds; they 

 copulate also like them, and conceive and bring 

 forth their young alive, which they afterwards 

 suckle with their miik. 



The cartiliganous sort are produced from large 

 eggs, like birds; which are also excluded the 

 womb like those of birds. 



The spinous kind are also oviparous ; but their 

 eggs are smaller, and they have spinas up and 

 down iheirfiesh to strengthen it. 



Willoughby thinks it would be yet more pro- 



b2 



