PROTEUS, a name given by many naturalists to certain animalcules remarkable for changefulness of form; on which account also, as the name proteus has been otherwise appropriated in science, they now receive the generic name amaa (Gr. vicissitude). They are protozoa, and ranked among the rli&opoda. See these heads. They are found in fresh water, and are generally from to of an inch in diameter, when they assume a somewhat globose form, which, however,t hey exchange for almost every imaginable shape, so that they cannot be described as having any proper or definite shape whatever. They Con sist of a transparent gelatinous substance (sarcode), or protoplasmic matter, which is divis ible into two layers, an outer (ectosarc) and an inner (endosare). The ectosarc is highly con tractile, and can be protruded into blunt finger-like processes called pseudo-podia (false• feet), by which the animal is enabled to move along, and by which it procures its food, such as adiatom, which it draws into its substance, there being no mouth ; and the effete matters arc ejected from any part of its circumference. These pseudo-podia can be
protruded from any part of the surface, and can be again retracted at the will of the animal. The only organs present in these animals is the nucleus, a dark, solid, refrac tive body, whose function is unknown ; the contractile vesicles, which are spaces filled with fluid, and pulsate rhythmically; and other spaces called food vacuoles.
Reproduction takes place either by fission, or a single pseudo-podia separates and becomes a fresh amoeba; or by the separation of a little mass of sarcode from the interior, the animal having become quiescent, and the nucleus and contractile vesicles disappearing. These little masses develop themselves into ordinary ammba.