HAL.—You are right, they never have seen any thing like it before; but, in its motion, it is like a large fly, and this is the season for large flies. The stone fly and the May fly, you see, occasionally drop upon the water, and the colour of your large fly is not unlike that of the stone fly; but if, instead of being here in the beginning of July, you had visited this spot, as I once did, in the beginning of June, you would have found more difficulty in catching grayling here, though not so much as in our English rivers—in the Test, the Derwent, or the Dove. POIET.—How could this be? HAL.—At this season the large flies had not yet appeared; the small blue dun was on the water, and I was obliged to use a fly the same as that which suits our spring and late autumnal fishing. The fish refused all large flies, but took greedily small ones; and, as usually happens when small flies are used, more fish escaped after being hooked than were taken; and these I found, the next day, were become as sagacious as our Dove or Test fish, and refused the artificial fly, though they greedily took the natural fly. PHYS.—These fish, then, have the same habits as our English salmons and trouts? HAL.—The principle to which I have referred in two former conversations must be general, though it has seemed to me, that they lost this memory sooner than the fish of our English rivers, where fly fishing is common. This, however, may be fancy, yet I have referred it to a kind of hereditary disposition, which has been formed and transmitted from their progenitors. PHYS.—However strange it may appear, I can believe this. When the early voyagers discovered new islands, the birds upon them were quite tame, and easily killed by sticks and stones, being fearless of man; but they soon learned to know their enemy, and this newly acquired sagacity was possessed by their offspring, who had never seen a man. Wild and domesticated ducks are, in fact, from the same original type: it is only necessary to compare them, when hatched together under a hen, to be convinced of the principle of the hereditary transmission of habits,—the wild young ones instantly fly from man, the tame ones are indifferent to his presence. POIET.—No one can be less disposed than I am to limit the powers of living nature, or to doubt the capabilities of organized structures; but it does appear to me quite a dream, to suppose that a fish, pricked by the hook of the artificial fly, should transmit a dread of it to its offspring, though he does not even long retain the memory of it himself. HAL.—There are instances quite as extraordinary—but I will not dwell upon them, as I am not quite sure of the fact which we are discussing; I have made a guess only, and we must observe more minutely to establish it; it may be even as you suppose—a mere dream.