Instinct is little or nothing more than inherited memory. But we are by no means satisfied that any definition which we have yet met with of the faculty known by the latter name is strictly correct. Whatever memory is, that inherited we are disposed to regard as instinct. And that the impressions on this faculty are transmissable in animals from parents to their offspring, we regard the migration of young birds, particularly those of a first brood, when the parents remain to attend to a second, as clearly substantiating. The bird now before the reader is a species that appears to perform the extended northward migration to which we have alluded, and is one of the most remarkable instances that has come to our knowledge. It was first described by us from a specimen obtained in the vicinity of Montreal, Canada, and the only instance of its having been observed since, has been by Dr. Heermann, in California; though if ever occurring in the middle or southern States on the Atlantic, in the same latitude as on the Pacific, it has escaped the researches of all previous naturalists or travellers. [Illustration: Plate 31 The Brown Hawk Buteo insignatus (_Cassin_)] Adult and young birds of this species were observed, and specimens were obtained by Dr. Heermann, who ascertained that it reared its young in California. For an opportunity to examine the specimen originally described by us in the present volume (p. 102), we are indebted to our lamented friend and correspondent, M. McCulloch, M. D., a naturalist of extensive acquirements, and an eminent physician, late of Montreal, but, we much regret to add, now recently deceased, and to John Pangman, Esq., of Grace Hall, in the vicinity of that city. Mr. Pangman had the kindness to interest himself, in conjunction with Dr. McCulloch, so much as to obtain the loan of the specimen from the Natural History Society of Montreal, in the museum of which it was deposited, and to bring it for our inspection to Philadelphia, and we shall not soon forget his evident and enlightened gratification, nor our own great pleasure, when we assured him that it was a bird hitherto unknown as an inhabitant of North America, and, as we then supposed, very probably an undescribed species, which we subsequently ascertained to be the case. This is one of the most remarkable of the rapacious birds which have been recently added to the ornithological fauna of the United States. It differs entirely in color from any previously-known American species, unless it may be supposed to approximate in that character to the little-known Harlan’s Buzzard of Audubon. It bears also some distant resemblance to one stage of plumage of the Black Hawk. The only information relative to the habits of this bird that we have in our power at present to lay before the reader, is the following from the Journal of Dr. Heermann: