The caterpillar mask had done its work, and having done its work, must die. Yet one can hardly call such dissolution death. As it hung suspended, all the marvellous mechanism which had formed a moving, eating, spinning, sentient being, was absorbed into the chrysalis it covered. Merely the outer empty shell remained. On the fourth day this shell split cleanly at the tail, and, from the opening, the hind part of the chrysalis emerged. It jerked from side to side, to all appearance aimlessly. Yet there was method in its madness. A side-swing forced it deep into the boss of silk, and, in a moment, the hooks that studded its extremity were fast entangled. The chrysalis had its _point d'appui_. [Illustration: ON THE CHRYSALIS HEAD WERE TWO SHORT-POINTED HORNS.] Again the old skin cracked, this time behind the neck. The chrysalis head was free. On it were two short, flattened, pointed horns. A jerky movement of the shoulders followed--first expansion, then contraction. At each expansion the old skin slipped a trifle upwards. Turn by turn the segments of the body did their work, until it lay in gathered folds about the tail, just as the pushed-off stocking lies about the ankle. But even so, the task was not completed. The skin must be got rid of. Its dull white mass, with dangling skeleton horns, was too conspicuous. Nature had armed the chrysalis with the needful tools, a grip attachment and a set of tiny sharp-edged hooks. The skin was fast entangled in the boss of silk. The chrysalis secured an independent foothold (using as stepping-stone the skin itself), spun itself from side to side, and cut the threads that bound it. It jerked lightly from leaf to leaf, until it reached the ground. The second change was accomplished. [Illustration: COLOUR AND FORM COMBINED THEIR SKILFUL MIMICRY.] [Illustration: ITS FORM THE FORM OF THE SALLOW-LEAF.] Outwardly the chrysalis was nothing but an extra leaf. Colour and form combined their skilful mimicry. Its colour was the green of the sallow; its form, the form of the sallow-leaf. For fifteen days it hung unchanged and motionless. On the sixteenth change was obviously impending. The upper segments had lengthened, the lower segments had darkened. On the twentieth day came the last great change of all. [Illustration: HE CHOSE THE LOFTIEST BRANCH OF THE LOFTIEST OAK IN THE FOREST.] It was a normal July day. Thunder was over the Downs. Now and again great rain-drops struck the sallow. They were few and far between, however. The thunder was content to grumble on the hills, leaving the valley to the sunshine. For all the midday heat the air was laden with moisture. This was at once both good and bad for the little Emperor, good because it made the bursting of his cerement easy, bad because it made the drying of his wings slow. Still he had no choice in the matter; his time had come, and he must make the best of it. [Illustration: WHITES.]