difference, marked by the terms, varieties, species, genera, families, etc.; and we have to discover the lines of descent by the most permanent characters, whatever they may be, and of however slight vital importance.

The similar framework of bones in the hand of a man, wing of a bat, fin of the porpoise, and leg of the horse — the same number of vertebrae forming the neck of the giraffe and of the elephant — and innumerable other such facts, at once explain themselves on the theory of descent with slow and slight successive modifications. The similarity of pattern in the wing and in the leg of a bat, though used for such different purpose — in the jaws and legs of a crab — in the petals, stamens, and pistils of a flower, is likewise, to a large extent, intelligible on the view of the gradual