ORN.—I have seen this fish in the rivers of Wales and Herefordshire, and have heard it asserted, on what appeared to me good authority, that it was a mule,—the offspring of a trout and a salmon. HAL.—This opinion, I know, has been supported by the fact, that it is found only in streams, which are occasionally visited by salmon; yet I know no direct evidence in favour of the opinion, and I should think it much more probable, if it be a mixed race, that it is produced by the sea trout and common trout. In a small river, which runs into the Moy, near Ballina in Ireland, I once caught in October a great number of small sea trout, which were generally about half-a-pound in weight, and were all _males_; and unless it be supposed, that the females were in the river likewise, and would not take the fly, these fish, in which the spermatic system was fully developed, could only have impregnated the ova of the common river trout. The sea trout and river trout are, indeed, so like each other in character, that such a mixture seems exceedingly probable; but I know no reason why such mules should always continue small, except that it may be a mark of imperfection. The only difference between the par and common small trout is in the colours, and its possessing one or two spines more in the pectoral fin. The par has large blue or olive bluish marks on the sides, as if they had been made by the impression of the fingers of a hand; and hence the fish is called in some places _fingerling_. The river and sea trout seem capable of changing permanently their places of residence; and sea trout appear often to become river trout. In this case they lose their silvery colour, and gain more spots; and in their offspring these changes are more distinct. Fish, likewise, which are ill-fed remain small; and pars are exceedingly numerous in those rivers where they are found, which are never separated from the sea by impassable falls; from which I think it possible that they are produced by a cross between sea and river trout. The varieties of the common trout are almost infinite; from the great lake trout, which weighs above 60 or 70lbs., to the trouts of the little mountain brook or small mountain lake, or tarn, which is scarcely larger than the finger. The smallest trout spawn nearly at the same time with the larger ones, and their ova are of the same size; but in the large trout there are tens of thousands, and in the small one rarely as many as forty,—often from ten to forty. So that in the physical constitution of these animals, their production is diminished as their food is small in quantity; and it is remarkable, that the ova of the large and beautiful species which exist in certain lakes, and which seem always to associate together, appear to produce offspring, which, in colour, form, and power of growth and reproduction, resemble the parent fishes; and they generally choose the same river for their spawning. Thus, in the