ANIMALCULES. Such animals as are clearly discernible only by means of micro scopes, for millions of millions of them might be contained in a thimble full of water, which is the best element for studying their motions. By the microscope many kinds of animalcules have been discovered, as different from each other as the horse from the mouse; some in deed so exceedingly minute, that a million would not equal in magnitude a large grain of sand, and, as more and smaller objects have ever been discovered, in proportion to the goodness of the glasses with which they have been 'viewed, it is highly probable that there are numberless other species, of a size much less than those already discovered. Every drop of water, and almost any fluid, except oils and ardent spirits, either does or will by stand ing exposed a few days in warm weather, swarm with living creatures. Some seem na
tural inhabitants of the fluids in which they are found ; others live there only occasionally, in the manner of gnats, which from eggs drop. ped in water by their parents, become swim ming animals; but, after a short time, shed their skins, appear in a form without resem blance to that before assumed, take wing, and claim kindred with the countless millions which rejoice in the air. The largest sort are thin and transparent ; they turn frequently, and have many feet, resembling a tail. Their motion is swift, and their frequent turns and sudden stops would intimate that they were hunting after their prey, probably insects in definitely smaller than themselves, that have hitherto escaped notice with the best glasses. Leenwenhoek says, no living creatures appear in rain water fresh descended, but after stand