The Natural History of the Salmon. 75 



November (Tweed) are our principal breeders. For 

 what purpose they enter the river seems clothed in 

 mystery." 



Dr. GtJNTHER. " The causes inducing migra- 

 tory Salmonoids to ascend rivers long before the 

 spawning season are not apparent. A number of 

 sterile fish, — that is, individuals which attain to 

 maturity at an unusually late period of their life, or 

 which are not again ready for propagation in one 

 year (although they may have bred in the preceding 

 year, and may breed again in the following), or 

 which remain barren all their lifetime — a number 

 of such sterile fish ascend rivers evidently for some 

 other purpose than to spawn." 



Mr. William Rochester says, the cause is 

 inexplicable. He says he has his own opinion on 

 the matter, ''an opinion not entertained by any 

 known writer whose works have fallen into my 

 hands," but he does not give us his opinion. 



Mr. Buckland says : " Having examined the 

 anatomical conditions of several of these clean-run 

 spring fish, and at the same time fully considered 

 this most difficult subject in all its bearings, I now 

 venture to propose a solution to the question. 

 These clean-run fish are a secondary migration of 

 salmon, a spring migration in contradistinction to 

 an autumn migration. I have shown that the 

 amount of fat upon the pyloric appendages will be 



