2 7 8 



How to obtain it. 



been badly used. The fins change with age, and it is, there- 

 fore, possible that a fish may at different times of its life have 



a forked tail or a square 

 tail. 



A tail sometimes ap- 

 pears to be forked because 

 it is not fully expanded, 

 and the accompanying 

 diagram (Fig. 46) will 

 show how a forked tail 

 may sometimes be made 

 into a square one, by ex- 

 panding a little. 



Many of the older 

 writers have defined species by the numbers of the pyloric caeca, 

 but these are found on examination to be ever-varying quantities, 

 even in forms that have been supposed to constitute distinct 

 species. From twenty-five to ninety the number of the former 

 seems to range, the average being between forty and fifty. The 

 usual temperature of a trout is nearly about the same as that of the 

 water in which it lives. Red spots may sometimes be seen on 

 trout after death that were not visible during life. 



Fig. 46. 



