First, "That they enter rivers to rid themselves of sea lice (_Monoculus piscinus_);" secondly, "That they forsake rivers to save themselves from being exhausted by residence in fresh water, and from having their gills devoured by a maggot (_Lernaea salmonea_)." The whole history of the Salmon contradicts this hypothesis. Another of these errors is, that it is asserted (Rep., 1824, p. 145), "That Salmon always return to the same river;" this is not probable, when we consider the circumstances in which they are placed during their residence in the sea. On the first of these opinions, I am not a competent judge; but I think that the fact that Salmon enter rivers nine or ten months before they are ready to spawn, is of itself sufficient to show that there are other reasons for their entering rivers than those connected with propagation. With respect to the second, I believe that after Salmon have once entered rivers, at least when they have ascended into the upper parts of them, they never offer to descend again until they have spawned. On the third opinion I would remark, that although I do not think that Salmon always come to the same river in which they were bred, yet I think they will do so if they can; and I think that the fact which I have mentioned of the Hodder, a smaller and a tributary stream to the Ribble, containing many more Salmon, as well as more Morts and Sprods, countenances this supposition, for why should the larger number of fish ascend the smaller river except for such a reason?