FISHES. 



605 



Their chief organ of natation is the caudal fin, but they are 

 distinguished from all other fishes by the manner in which they use 

 this oar. When turned upon their side this organ is not horizontal, but 

 vertical, and strikes the water vertically up and down. They advance 

 through the water but very slowly, compared to the motion of other 

 fishes. They ascend or descend m the water with great promptitude, 

 but they cannot turn to the right or left with the same facility as other 

 fishes. This property of rising or sinking in the water with facility is 

 the more useful to them, inasmuch as the greater part of their existence 

 is passed at the greatest depths, where they draw themselves along the 



Fig. 385. — The Sand-eel (Ammodytes ancea) 



sands at the bottom of the sea, and often hide themselves from their 

 enemies. Among the Fleuronectidce, soles, turbot, flounders, and 

 plaice may be noted. 



The soles have the body oblong, the snout is round, nearly always 

 in advance of the mouth, which is twisted to the left side and furnished 

 with teeth on one side only, while the eyes are on the right side. The 

 dorsal fin commences about the mouth, and extends up to the caudal 

 or terminal fin. The Common Sole, Solea vulgaris (Fig. 386), is 

 plentiful in the Channel, along our coasts, and especially in the 

 Mediterranean. It is brown on the right and whitish on the opposite 

 side. Its pectoral fins are spotted black ; the scales rugged and 

 denticulate ; its size seems to vary according to the coast it frequents. 

 Off the mouth of the Seine soles are sometimes taken eighteen and 

 twenty inches in length. There are several modes of taking them, 



