In animal life Nature reveals this in a million phases. Animals placed in the darkness of the Mammoth Cave gradually have the sense of sight weakened and the senses of smell, touch and hearing intensified. Nature watches over all animals, making their color harmonize with the general tone of their surroundings to protect them from their enemies. Those arctic animals which in the summer inhabit regions free from snow, turn white when winter comes. In the desert, the lion, the camel and all the desert antelopes have more or less the color of the sand and rocks among which they live. In tropical forests parrots are usually green; turacous, barbets and bee-eaters have a preponderance of green in their plumage. The colors change as the habits of the animals change from generation to generation. Nature, by her Reserve Power, always meets the new needs of animals with new strength,—new harmony with new conditions. About forty-five years ago three pairs of enterprising rabbits were introduced into Australia. To-day, the increase of these six immigrants may be counted by millions. They became a pest to the country. Fortunes have been spent to exterminate them. Wire fences many feet high and thousands of miles long have been built to keep out the invaders. The rabbits had to fight awful odds to live, but they have now outwitted man. They have developed a new nail,—a long nail by which they can retain their hold on the fence while climbing. With this same nail they can burrow six or eight inches under the netting, and thus enter the fields that mean food and life to them. They are now laughing at man. Reserve Power has vitalized for these rabbits latent possibilities because they did not tamely accept their condition, but in their struggle to live learned _how_ to live. In plant life, Nature is constantly revealing Reserve Power. The possibilities of almost infinite color are present in _every_ green plant, even in roots and stems. Proper conditions only are needed to reveal them. By obeying Nature’s laws man could make leaves as beautifully colored as flowers. The _wild_ rose has only a single corolla; but, when cultivated in rich soil, the numerous yellow stamens change into the brilliant red leaves of the full-grown cabbage-rose. This is but one of Nature’s miracles of Reserve Power. Once the banana was a tropical lily; the peach was at one time a bitter almond. To tell the full story of Reserve Power in Nature would mean to write the history of the universe, in a thousand volumes.