In addition to the world of life that is visible, there is a world of life that is invisible,--a microscopic realm of animalcula, which "live and move and have their being" in every element of life, and in every life, and yet are so minute as to be imperceptible to the naked eye. These invisibles, or infusoria, abound everywhere and in everything. They pervade the sea, the land, the air. They swarm in every drop of water, and revel in every morsel of food. We can neither eat nor drink without infringing on their domain and consigning myriads of them, perhaps, to an unprovoked destruction. They are almost as various in grade, size, and shape, as they are numerous. Some are hideous, while others are comely. They feed on each other, the superior on the inferior, and are ever struggling for life and for the mastery. They engage in the "battle of life" to sustain life, and hold to the doctrine that "to the victors belong the spoils." It is an ascertained fact that a speck of potato-rot, the size of a pin-head, contains hundreds of these little ferocious animals, fighting and devouring each other without mercy and without cessation. What seems still more surprising is that they probably have a perfect organization,--heart, lungs, stomach, circulation of blood, and are endowed, perhaps, with all the five senses. Infinite numbers of them, it is supposed, exist in so minute a form that no microscope, however great its power, can detect them. Nor need we doubt that even these living invisibles are beset with parasites vastly minuter than themselves, which feed and breed on their surfaces. In the very blood-circulation of the minutest, it is not improbable that other infusoria, still more minute, swim and prey upon each other. The uses for which this invisible world of life were created, though doubtless for a wise purpose, cannot be comprehended. Yet it is evident that every living thing, however minute, has a destiny of some sort, ever progressing, it may be, from a lower to a higher sphere,--from the material to the spiritual, from the finite to the infinite. "All are but parts of one stupendous whole, Whose body Nature is, and God the soul."