The phosphorescence of animals is amongst the most surprising of nature’s phenomena, and it is not the less so from our almost entire ignorance of the cause of it. Many very poetical fancies have been applied in description of these luminous creations; and imagination has found reason why they should be gifted with these extraordinary powers. The glow-worm lights her lamp to lure her lover to her bower, and the luminous animalcules of the ocean are employed in lighting up the fathomless depths where the sun’s rays cannot penetrate, to aid its monsters in their search for prey. “The lamp of love--the pharos--the telegraph of the night,--which scintillates and marks, in the silence of darkness, the spot appointed for the lover’s rendezvous,”[109] is but a pretty fiction; for the glow-worm shines in its infant state, in that of the larva, and when in its aurelian condition. Of the dark depths of the ocean it may be safely affirmed that no organized creation lives or moves in its grave-like silence to require this fairy aid. Fiction has frequently borrowed her creations from science. In these cases science appears to have made free with the rights of fiction. The glow-worms (_lampyris noctiluca_), it is well known, have the power of emitting from their bodies a beautiful pale bluish-white light, shining during the hours of night in the hedge-row, like crystal spheres. It appears, from the observations of naturalists, that these insects never exhibit their light without some motion of the body or legs;--from this it would seem that the phosphorescence was dependent upon nervous action, regulated at pleasure by the insect; for they certainly have the power of obscuring it entirely. If the glow-worm is crushed, and the hands or face are rubbed with it, luminous streaks, similar to those produced by phosphorus, appear. They shine with greatly increased brilliancy in oxygen gas and in nitrous oxide. From these facts may we not infer that the process by which this luminosity is produced, whatever it may be, has a strong resemblance to that of respiration? There are several varieties of flies, and three species of beetles of the genus _Elater_, which have the power of emitting luminous rays. The great lantern-fly of South America is one of the most brilliant, a single insect giving sufficient light to enable a person to read. In Surinam a very numerous class of these insects are found, which often illuminate the air in a remarkable manner. In some of the bogs of Ireland a worm exists which gives out a bright green light; and there are many other kinds of creatures which, under certain circumstances, become luminous in the dark. This is always dependent upon vitality; for all these animals, when deprived of life, cease to shine.