THE 



FRESH-WATER FISHES OF EUROPE. 



CHAPTER I. 



INTRODUCTION. 



The Orders of Fresh-water Fi.shcs — Characters used in Classification of Fishes — The Forms of 

 Fresh-water Fishes — The Structure of the Fins and the Fin FormuLe — The Scales— Org-ans 

 of the Senses— The ]\Iouth — The Operculum and Gill-arches — ^The Skeleton — Air-bladder 

 — Digestive Organs — Repi-oductive Organs — Growth — Geograpliical Distribution — Table 

 showing Range of Species — Table showing Classification of Fishes described. 



We commonly understand by Fresh-water Fishes such as live in rivers^ ponds, 

 and lakes. The majority o£ these species are incapable of existing in salt 

 water, and rarely travel far in the stream or water which is their home. 

 Other species are hardier, and not only endure sea-water without difficulty, but 

 a mig-ration to the sea, like an autumn holiday, is a more or less necessary 

 condition of existence. Among- such migratory fishes the European seas offer 

 familiar examples in the Sturgeon, Salmon, migratory Trout, and Eels. Yet 

 the circumstance that many Trout pass the whole of their lives in fresh water 

 leads us to believe that the constitution of a fish is somewhat elastic, and 

 capable of accommodating itself to more restricted conditions of existence. 

 While, on the other hand, the presence in brackish waters of the Baltic Sea of 

 Perch, Pike, Roach, and other familiar fresh-water types, makes it probable 

 that after a fish has once become a denizen of fresh waters, it may again 

 return to a salt-water life. About the mouths of rivers there are always 

 marine fishes, which come into the shallow and sheltered places to spawn; and 

 as some of them make their way far up the waters, they occasionally become 

 acclimatised, and in any case may be mentioned as fishes found in fresh waters 

 during their wanderings. Among such are certain of the flat fishes, like the 

 Flounder, and, in some localities, the Plaice and Sole ; the Whitebait ; and, 

 in some countries, species of Atherina and Grey Mullet. So numerous are 

 these types that it would h? impossible to describe them all without appearing 

 anxious to augment the province of Fresh-water Fishes at the expense of their 

 marine relations. Nevertheless, it is impossible to ignore the existence of such 

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