When the zeal of a collector adds a new species to those already known, by finding the fragment of a butterfly’s wing that had been for millions of years in a seam of coal, how many considerations are forced upon the mind! Our sensitive nerves are comparatively seldom troubled by the perceived presence of dead creatures. With the exception of our own food, such sights are pretty well confined to the carcase of a dog floating on a pool, the feathers of a torn bird, a parched mole, and a sprinkling of blue-bottles in an unused room. Yet countless millions of creatures are annually dying, ready and willing to become fossils. Fossils, however, they do not become, simply because other creatures eat them up. For this reason alone, not one in ten thousand of any particular terrestrial species is likely to become fossil, because to some creature or another it is almost sure to be good eating, and therefore in the living state or the dead, sure to be ravenously seized upon and devoured. Some forms of marine life are indeed represented by a wonderful number of specimens or fragments of specimens. Silicious and calcareous exuviæ of minute creatures deposited in the still depths of the ocean may be preserved by myriads, but neither these ‘in number numberless’ nor the giant-bones of ancient Saurians convey any adequate notion of the whole population of the globe at any one era. The palæontologist, guiding himself only by prominent details of this description, would be like a child over a child’s history of England, to whom the fabric of the Constitution and the Reformation of the Church seem matters obscure, and scarcely worthy of notice, while Alfred burning the cakes, and Henry VIII in his well-known character of Bluebeard, stand out in bold relief.