OF GREAT BRITAIN. n 



migration is not confined to the Parrs on going to 

 the sea, or to the Smolts on their return from it, 

 some as Grilse and some as spring Salmon, but 

 that it also extends to the old and adult Jish after 

 spawning one portion of these latter coming back 

 into the rivers during the following summer, and 

 the rest not until the spring succeeding it ; in other 

 words (and this is the gist of the whole), that at 

 least a proportion of Salmon spawn only on every 

 alternate year. 



An analogous fact was observed by Dr. Davy 

 with regard to the spawning of the common Trout. 

 Dr. Davy was in the habit of opening the fish he 

 caught, and by this means he discovered that, as 

 the spawning-season approached, only about one 

 half of the females had visible eggs, whilst in the 

 other half there were no signs of the development of 

 the ova. Charr, also, are frequently taken in Win- 

 dermere in high condition in October and Novem- 

 ber, which is their regular spawning-season, a 

 fact which would seem to point to the possibility 

 of the rule of alternate spawning-years holding 

 good in the case of all fish here included under the 

 genus Salmo. 



The design of this law or instinct which, when 

 once apprehended, will be found to explain many 

 of the perplexities in the history of the Salmon 

 is intelligible enough, viz., to ensure as large a 

 supply of clean fish throughout as large a portion 

 of the year as possible, and to enable each river to 



