6 INDIAN FRESH-WATER FISHES. 



the several species. In short, it is now possible, thanks 

 to the painstaking labours of onr predecessors, to 

 attempt a popular work on this subject without in- 

 curring the clanger of running into serious error. 



So much for the difficulties ; but the study of 

 Ichthyology has one great advantage, which is this. 

 Fishes are very slightly subject to variations at dif- 

 ferent ages and under different circumstances. With 

 birds one species may have a plumage for winter use, 

 and a different dress in summer, or the young may 

 have very little resemblance to the old bird, or the 

 male to the female. With insects the larval and 

 pupal forms have to be studied as well as the mature 

 insect, and similar uncertainty occurs in other classes 

 of the animal kingdom. With fish this is rarely the 

 case ; the sexes hardly ever differ in appearance, and 

 the young of most species possess all the characteristics 

 of the full-grown fish (there are exceptions of 

 course to this as to most general rules). It is as 

 easy, for instance, to identify a mahaseer of two inches 

 in length, as one of four feet. 



In India the study has special advantages. Hardly 

 ai3y where in India are specimens not obtainable at 

 any time of year, and in great variety : each tank or 

 stream has an interest of its own, and if a person is 

 unable to go out and collect for himself, it is always 

 easy to employ fishermen, who bring specimens to the 

 house where they can be examined at leisure. 



A matter of great interest connected with the 



