Since in the time most remote men depended upon animals almost entirely for their food, it is probable that animals were the objects that made the most vivid impressions on them, and, therefore, that stories of animals belong to this most primitive stage. At this time, too, it is likely that the worship of animals arose, for almost every tribe of savages had a sacred animal which, except in rare instances, it was never allowed to kill and from which it often imagined itself descended. After many ages, mankind began to till the ground, and to raise grain and vegetables, then plants and trees were more especially observed by them, and the mythical stories have, in consequence, more about plants and trees in them; and, as they had sacred animals, they had also sacred trees or plants, and worshipped them or imagined themselves descended from them. Then as men progressed in their powers of observation they saw natural phenomena more and more. The succession of night and day impressed itself upon them, they took note of the motions of the sun, the moon and the stars, clouds caught their attention, storms filled them with awe and fear as the lightning flashed and the thunder roared and rattled in its might. The wind laughed in summer breezes or howled in wintry blasts and they noticed it, and as soon as their attention was fully aroused to all these wonders of nature, they began to think of them, as not only endowed with powers like their own, but as living beings. First, they frequently personified nature as animals, then as human beings, and as they had worshipped sacred animals and sacred plants and sacred trees, now they worshipped these gods of nature; and as they invented tales about the animals and the trees, so they invented tales about these gods of nature. As one would expect, the stories about animals and trees would often be mingled with the new stories of the nature gods, and sometimes changed so that one would hardly recognize them. And then, again, a story told about a nature god in one part of the world would, on account of the early wanderings of the human race from one land to another, be added as an ornament to a story told in another part of the world, like the ornaments on the Christmas trees in the castle. Again, whole myths would be transported, and as they reached different countries they would be changed somewhat so that they would reflect the manners or the knowledge of that particular country. A strange thing, however, about many myths is that those in one part of the world are so much like those in another part of the world that it would seem as if they must have been invented by the same people. Not only are there myths in India and Greece which are very much alike, but there are myths in Scandinavia and North America and South America that strongly resemble each other and those of Greece and India.