It is a remarkable fact that only a few whales and porpoises eat fish or the flesh of other whales. The large toothed-whales, including the cachalot or sperm whale, and also the Ziphius-like beaked whales, live upon cuttle-fish. And it seems that they know where to hunt for this special article of diet and how to find it in quantity (probably at great depths in the ocean), which naturalists do not. Many new kinds of cuttle-fish have been discovered by examining the contents of the stomach of captured whales. The sperm whale feeds on monster squid and poulp such as we rarely, if ever, see alive or washed up on the shore. The hide of these cuttle-fish-eating whales and porpoises is scratched and scarred by the hooks attached to the suckers on the arms of the great cuttle-fish, and a test of the genuine character of ambergris which forms as a concretion in the intestine of the sperm-whale is that it contains fragments of the horny beaks and hooks of the cuttle-fish digested by the whale. The food of the whalebone whales consists of minute crustacea and of the little floating molluscs known as _Clio borealis_, as big as the last joint of one's little finger, which float by millions in the Arctic Ocean. The whalebone whales, after letting their huge mouths fill with the sea-water in which these creatures are floating, squeeze it out through the strainer formed by the whalebone palisade on each side--by raising the tongue and floor of the mouth. The water passes out through the strainer, and the nourishing morsels remain. Some fossil jaws and skulls of whales from miocene and older tertiary strata are known which tend to connect the toothed whales with those mammals not modified for marine life. But the approach in that direction does not go very far. The extinct whales called Squalodon have tusk-like front teeth and molars which have the outline of a leaf with a coarsely "serrated" edge. The bones of the face are also, in them, more like those of an ordinary mammal than is the case with modern toothed whales. The snout is not so long, and the bones which form it are a little more like those of a fox's snout than are those of the dolphin's "beak." But on the whole it is astonishing how little we know of fossil whales. We have yet to discover ancestral forms possessing small hind legs, but whale-like in other features. Some day a lucky "fossil-hunter" will come upon the remains of a series of whale-ancestors probably of Eocene age, and we shall know the steps by which a quadruped was changed into a cetacean--just as we have recently learned the history of the development of elephants. We know even less about the ancestry of bats and the steps by which they acquired their wings than we do about the history of whales. These discoveries await future generations of men when "cuttings" and "pits" and quarries shall have been made in the rest of the earth's surface to the same extent as they have been in Europe and in parts of the American continent.