Infusoria
the name first given by Otto Frederick Müller to the mostly microscopic animalculæ developed in organic infusions. A drop of water from a weedy or other pool or ditch, viewed by the microscope, contains them in countless numbers. Pritchard divided them into Bacillaria, which were clearly vegetable, Phytozoa on the borderland between animals and plants, and Protozoa, Rotatoria, or Rotifera, and Tardigrada, clearly animal. Professor Huxley ele vated them into one of the eight primary groups into which he divided the animal kingdom. They have neither vessels nor nerves, but possess internal spherical cavities. They move by means of cilia or variable processes formed of the substance of the body, true feet being absent. They occur everywhere, in salt as well as in fresh water. One, Noctiluca, is believed to take a great share in producing the phosphorescence of the ocean.