PARTS OF ANIMALS, IV. xiii. 



need no such limbs. But also (6) they are essentially- 

 blooded creatures, which means that if they have four 

 fins they cannot have any legs or any other limbs of 

 the sort ; so they have the fins because they are 

 swimmers and do not have the feet because they are 

 not walkers (when an animal has feet it has them 

 because they are useful for moving about on land). 

 The Cordylus,^ however, has feet in addition to its 

 gills, since it has no fins, but only a scraggy flattened- 

 out tail. 



Excluding flat-fish (like the Batos and Trygon), fish Fins, 

 have four fins : two on their under and tw^o on their 

 upper surface, never more, for then they would be 

 bloodless animals. Almost all fishes have the two 

 upper ^ fins, but some of the large, thick-bodied fishes 

 lack the under ^ two — as for instance the eel and the 

 conger, and a sort of Cestreus that is found in the lake 

 at Siphae.'^ Fishes that have even longer bodies than 

 these, and are really more like serpents (as the 

 Smyraena^), have no fins at all, and move along by 

 bending themselves about : that is, they use the 

 water just as serpents use the ground. And in fact 

 serpents swim in exactly the same way as they creep 

 on the ground. The reason why these serpent-like 

 fishes have no fins and the reason why serpents 

 have no feet are the same, and this has been stated 

 in the treatises on the Locomotion and Movement of 

 Animals. f {a) If they had four motion-points, their 

 movement would be poor, because the fins would 



<* In Boeotia, on the south coast near Thespiae ; now 

 Tipha. Aristotle refers to this Cestreus of Siphae again, 

 De incessu an. 708 a 5. Cf. also Hist. An. 504 b 33. 



* Probably Muraena Helena. 



' See Be incessu an. 709 b 7 ; perhaps the other passage 

 which Aristotle has in mind is 690 b 16, in this book. 



0-1 419 



