OF GREAT BRITAIN. 49 



3. Length of head. The disproportionate size of 



the head in the Great Lake Trout is very 

 remarkable, it being usually little less than 

 one-fourth of the total length of the fish, tail- 

 fin included, whilst in the Yellow Trout it 

 is commonly not much more than one-fifth. 



4. Tail-fin. The tail-fin in the Great Lake Trout 



(as shown in the illustration), is nearly square 

 at the end, and is considerably wider than the 

 widest part of the body, whilst in the Com- 

 mon Yellow Trout it is very obviously nar- 

 rower than the same measurement. 



By bearing these characteristics in mind, the 

 student of ichthyology should be readily able to 

 distinguish with tolerable certainty between the 

 two species. I say with " tolerable certainty," be- 

 cause an intimate knowledge of the distinguishing 

 characteristics of the various species viSalmonida 

 is very difficult to acquire, and is, indeed, rarely 

 attained except by the scientific ichthyologist, or 

 by the fisherman (angler) who has passed half a 

 life-time on the river bank, and who ekes out a 

 little " science " with a great deal of " practice." 



Except in some of the more permanent charac- 

 teristics already alluded to, the varieties to be 

 found amongst Trout are simply endless. Its 

 colouring and even its shape are susceptible of 

 infinite difference, and vary as much as the quali- 

 ties of waters (whether in sources or feeders), 



E 



