66 SALMON FISHING IN THE TWEED 



summer of its spring migration, weighing about a 

 pound and a half upon an average. It afterwards 

 increases about a pound and a half a year ; but is 

 seldom seen above six or seven pounds, though it 

 probably attains to a much greater weight. 



By the aid of the cruive, Mr. Shaw traced this 

 fish from the orange fin of three ounces to the 

 hirling or whitling, up to the sea trout of seven 

 pounds ; and he has now a specimen in his posses- 

 sion exhibiting the four several marks he had put 

 on it in the course of its annual migrations. At 

 the size of six pounds the central rays of the tail 

 were considerably increased in length, so much so 

 in the males that their tails became actually 

 rounded: the fish altogether at this time loses a 

 great deal of its former elegance. The tails of the 

 females of a corresponding age are more square, 

 and their general shape is more slim. 



These fish may be crossed with salmon ; I mean 

 that by artificial impregnation hybrids may be thus 

 produced. Mr. Shaw says in a letter to me, dated 

 November 25th, 1840 : " I put some of your sug- 

 gestions regarding the ova of the salmon, and the 

 common trout, sea trout, and salmon, into practice 

 about a month ago, and shall let you know the 

 result." The following year I had the pleasure of 

 a letter from him, dated October 14th, 1841, saying 

 that " The hybrids which I produced by artificial 

 impregnation last autumn are all in a very healthy 

 state, the cross not having in the slightest degree 

 affected their constitution. Those produced between 

 the salmon and the salmon trout (Salmo Trutta] 

 appear to partake more of the external markings, 



