SLOTH, AN ANIMAL WHICH KEEPS TO TREES AND IS ALMOST HELPLESS ON THE GROUND 273 WART HOG, ONE OF THE UGLIEST ANIMALS TO SEE 304 MALAY TAPIR, RELATED TO THE PIG AND THE RHINOCEROS 304 MARKHOR, AN ASIATIC WILD GOAT 305 MOUNTAIN SHEEP OR BIGHORN OF THE ROCKY MOUNTAINS 305 THE KUDU, OR STRIPED ANTELOPE, OF AFRICA 312 HEAD OF THE GREATER SABLE ANTELOPE 312 HEAD OF ALASKAN MOOSE 312 AXIS, OR SPOTTED DEER OF THE EAST INDIES 313 AMERICAN DEER WITH HORNS IN VELVET 313 WOLVES IN WESTERN NORTH AMERICA 336 BEAR IN A ROCKY MOUNTAIN FOREST 337 BAT, WITH YOUNG BAT IN EACH POUCH 352 BLACK SPIDER MONKEY 353 RUFFED LEMUR, ATTRACTIVE BY ITS COLORING 353 MANDRILL, MOUTH OPEN TO SNARL 368 GORILLA, SOMEWHAT THOUGHTFUL 368 CHIMPANZEES, IMITATING SOME OF THE WAYS OF MAN 369 CHAPTER I HOW THE GLOBE WAS STOCKED WITH LIFE Ever since man began to think in the connected way that follows self-consciousness, he has pondered, with a mixture of fear, reverence, and curiosity, on the nature of life and its origin. The world in which he found himself was a vast mystery which, very crudely at first, he sought to penetrate. All his paths of thought led him circling back to himself as the greatest mystery of all. He struggled with the problem for thousands of years, framing fanciful guessworks, erecting elaborate structures of logic on foundations of error, emotion, and presumption, fashioning beautiful fables and theories (and waging wars to compel other men to accept them), yet found no better solution than that life must be a gift from some unknown, perhaps unknowable, source. Even lately, learned philosophers, such as Helmholtz and Kelvin, supposed it brought to the earth (in germs) by meteorites--fragments of exploded planets that had borne life before they went to destruction; or, like Arrhenius, postulated an impalpable dust, or "panspermia," scattered through all space and borne from the atmosphere of one planet to another. But all such hypotheses only threw the question of origin one step further back.