Notwithstanding all this, she loves, does that great Soul of Harmony which is the unity of the world; she loves all beings, and by alternations of pleasure and of pain, instructs them and compels them to ascend. But to ascend, to pass into a superior grade, they must first exhaust all that the lower one can furnish of trials more or less painful, of instinctive art, and of stimulants to invention. They must even have exaggerated their species, perceived its excesses, and, by contrast, be inspired with the craving and the need of an opposite one. Progress is thus made by a kind of oscillation between contrary qualities, which by turns are separated from life, and incarnated with it. Let us translate these divine things into human language, familiar, indeed, and little worthy of the grandeur of such things, but which will make them understood: Nature, having long delighted to make, unmake, and remake the Medusæ, thus infinitely varying the theme of infant liberty, smote her forehead one morning, and said--"I have a new and a delicious idea. I forgot to secure the life of the poor creature. It can continue only by the infinity of number, the very excess of its fecundity. I must now have a creature at once better guarded and more prudent. It shall if need be, be timid, even to excess, but above all, it is my will that it shall survive." These timid creatures, when they appeared, were of a prudence carried to its extremest limits. They shut themselves in, shunning even the light of day. To save themselves from the rude contact of sharp and ragged stones, they employed the universal means, a glutinous mucus from which they secreted an enveloping tube, which elongated in proportion to the length of their journey. A poor expedient, that, which kept these miners, the Tarets out of the light and out of the free air, and which compelled an enormous expenditure of their substance. Every step cost them enormously; a creature thus ruining itself that it may live, can only vegetate--poor, and incapable of progress. The next resource was not much better, temporarily to bury themselves, going below the sands at low water, and rising to the flood-tide; the resource of the Solen. A varying life that, fugitive twice a day, and consequently full of anxiety. Among very inferior creatures a thing as yet obscure, which was in time to change the world, began to appear. The simple sea stars had in their fine rays a certain support, a sort of jointed carpentry, and on the outside some thorns, suckers, which could be thrust forward or withdrawn at will. An animal very humble, but timid and serious, seems to have profited by this coarse specimen. It said, I imagine, to Nature: