We know that on land our fire flies, by their fire give the signal of the bashful yet eager lover who thus betrays her retreat, and decoys her mate. Have the Medusæ this same sense? We know not; but thus much is certain, that they yield at once their flame and their life. The fecund sap, their generative virtue, escapes and diminishes at every gleam. If we desire the cruel pleasure of redoubling this brilliant faëry, we have only to expose them to warmth. Then they become excited, flash, and become beautiful, oh, so exquisitely beautiful--and then the scene is at an end. Flame, love, and life, all are at an end--all evanish for ever. CHAPTER VII. THE STONE PICKER. When the excellent Doctor Livingstone visited the poor Africans who have so much difficulty in defending themselves against the Lion and the slave merchant, the women, seeing him armed with all the protecting arts of Europe, invoked him as their friend and providence in these touching words--"Give us sleep!" And such is the prayer which all beings in their own language address to Nature. All desire, and all dream of, security. We cannot doubt of that when we note the ingenious endeavors which are made to obtain it. Those efforts have given birth to the arts. Man has not invented one, which animals had not previously invented, under that strong and abiding instinct, the desire of safety. They suffer, they fear, they desire to live. We must not assume that creatures little advanced, and as it were embryonic, have, therefore, but little sensibility. The very contrary is certain. In every embryon, that which first appears, is the nervous system, that is to say, the organ and capacity of feeling and of suffering. Pain is the spur by which the creature is urged to foresight and expedients. Pleasure serves the like purpose, and it is already observable even in those which seem the most cold. It has been observed that the snail, after the painful researches of his love, is singularly happy on meeting again the loved object. Both of them with a touching grace wave their swan-like necks, and bestow upon each other the most lively caresses. Who is it that tells us this? The rigid, the very exact Blainville. But alas! how largely and how widely is pain distributed! Who has not noted with pity the painful efforts of the shell-less mollusc, as he grovels along on his unguarded belly? Painful but faithful image of a foetus untimely torn from the mother by some cruel chance, and cast upon the ground naked and defenceless. The poor mollusc thickens and indurates his skin as well as he can, softens the asperities of his road, and renders it slippery. But at every contact with the ragged or pointed stones, his writhings and contractions only too plainly show how great is his sensibility to pain.