FISHES 279 



similar range. It can easily be distinguished from the Cod by 

 the black colour of the lateral line, and the presence of a rounded 

 black patch just behind the gill cover. A third allied but smaller 

 species is the Whiting {Gadus merlangus), the range of which 

 is restricted to the seas of Northern Europe. It has a dark 

 patch at the root of each pectoral fin and lacks the barbel of the 

 two preceding species. 



A small number of the species included in the Cod Family 

 are fresh-water, and the best known of these is the Burbot or 

 Eel-pout {^Lota vulgaris), abundant in many of the rivers of 

 North America and North and Central Europe. In England 

 it is found in some of the rivers which flow into the North Sea. 

 There are two dorsal fins, of which the second is very long and 

 low, while on the under side of the body there is an anal fin of 

 similar character. A barbel is present as in the Cod. 



2. Fiat-Fish Family. — The familiar food-fishes which make 

 up this family are distinguished by a remarkable want of sym- 

 metry, which has no parallel among Vertebrates. One might at 

 first sight imagine that the dark and light surfaces of the body 

 were respectively upper and lower. A little closer inspection, 

 however, would show that a long dorsal fin ran along one edge 

 of the body and a long anal fin along the other; and further, 

 that each surface had a lateral line running along it, and possessed 

 both gill-cover and paired fins, thus conclusively proving the 

 broad surfaces to be the sides. In some cases the dark upper 

 side is the right one and in others the left. A flat-fish starts 

 life with the same kind of symmetry as an ordinary fish, one 

 eye being on the right and the other on the left, while the 

 body is maintained in the usual position ; but as development 

 proceeds, and the body gets more flattened, one side becomes 

 pigmented, and the eye of the contrary side is displaced so as 

 to be near its fellow. We may take as well-known examples, 

 Turbot, Plaice, and Sole. 



The Turbot [Rhombus maximus) (fig. 34) is a large broad 

 fish limited to European seas, and with the eyes on the left side. 

 In the Plaice {Pleuronectes platessa), which though broad is a 

 much smaller fish, the dark, eye-bearing surface is the right 

 side. It is marked by large orange spots. This species ranges 

 along the west coast of Europe and extends as far north as 

 Iceland. The Common Sole [Solea vulgaris) also has the eyes 



