50 CHANGE OF COLOUR IN FISH. 



in Dumfries-shire, amidst the hills of Queensbery, where 

 three mountain streams, all of different character, meet 

 — the one proceeding from a moss ; the other running 

 over a clear channelly bed ; and the third, from its 

 clayey banks and bottoms, exhibiting a milk-and-water 

 aspect, like the ' flavus Tiberis ' (or Albula) of Italy. 

 Now the trouts in all these streams were of the same 

 generic type ; but differed, notwithstanding, in exter- 

 nal appearance or colour. The moss race were of the 

 Roderick Dhu tint — aspect grim and swarthy : the clear 

 channel produced those of a brightly spotted appearance ; 

 and the clay bottom exhibited a correspondingly bluish 

 race. Now, you might convert the blue fish into bright, 

 and the bright again into black, by merely transferring 

 them into the corresponding streams. This often took 

 place, more or less, after what is called a thunder 

 plump, which falls partially, and is quite local. I have 

 seen one of these streams overflowing its banks, and 

 carrying all before it, whilst its two mountain sisters 

 remained calm and unmoved. Upon the ebbing of this 

 partial flood, the trouts in the two conjoining streams 

 immediately rush in quest of food (particularly after a 

 long drought) into the other ; and, in less time than any 

 one who has not marked the fact could believe, they all 

 become of the same appearance. Upon returning again 

 into their native waters, they reassume their former 

 colour. Fill your basket with fish from all the three 

 streams, and in a little while that part of the bodies 

 which presses against the others will exhibit the same 

 appearance, whilst the other parts will remain as before ; 

 and hence the clouded aspect they exhibit. I once 



