So we see that the polar bear has become more than half a water-animal, and gives us the first hint that some milk-givers may take to a thoroughly sea life. Neither among the wolves nor the felines do we find any animals taking entirely to the water; but in the weasel family, which comes near to the bears, we have the otters, and among the bears themselves their polar cousin, which reminds us that there is another great division of flesh-feeders which we must study in the next chapter--the walruses, seals, and sea-bears, the porpoises, dolphins, and whales, which with finned paddles have struck out quite a new line of life, and imitated the fish so well that they are often wrongly classed among them. [Illustration: EUROPE IN THE AGE OF ICE] CHAPTER XI. HOW THE BACKBONED ANIMALS HAVE RETURNED TO THE WATER, AND LARGE MILK-GIVERS IMITATE THE FISH. “On revient toujours à ses premiers amours,” says the French song. But who would have thought that, after rising step by step above the fish, and tracing the history of the backboned animals through their development in the air and over the land, till we brought them to a stage of intelligence second only to man, we should have to follow them back again to the water and find the highly gifted milk-givers taking on the form and appearance of fishes? Nevertheless it is so, for seals and whales are as truly flesh-eating milk-givers as bears and wolves; nor are they much behind them in intelligence, for we all know how teachable and affectionate seals and sea-lions are, while what little is known of the life of whales shows that they are devoted mothers, and their well convoluted though small brains are a proof that they are by no means wanting in intelligence. Yet the whales and dolphins, at any rate, have not only adopted a sea life, but have limbs so like a fish’s fins that we can scarcely call them by any other name, and they are so completely water animals that they cannot even return to the land. Now we should be quite puzzled to account for such curious forms as these warm-blooded animals, half transformed into fish, if it were not that we know of several land animals belonging to different groups which have gone part of the way towards a fish life. Thus among the reptiles we have the oceanic turtles and the sea snakes; among birds the penguins, whose wings have almost become fins. Then among the milk-givers we have the web-footed Duck-billed Platypus, the Yapock or web-footed opossum of South America, the Desman and the Beaver, the Polar Bear, and last but not least the Otters, web-footed animals nearly allied to the weasels, which seek their food entirely in the water.