RHIZOPODA (Gr. rhizon, a root, and poda, feet), an important class of the lowest of the animal subkingdoms, the protozoa. In all the organisms of this class, the body is composed of a simple gelatinous substance, to which the term "sareode" is applied; and Sion, all, locomotion is performed by the protrusion of processes which, from their funo in are termed " pseudopodia." or false feet. As in the case of all the protozoa, except the infusoria, there is no mouth or intestinal tube.
As a typical form of rhizopod, the ameba a minute animal readily obtained in this country. may be taken. On placing one of these organisms (obtained from a pond, or from it bottle containing souse vegetable infusion) under the microscope, it is seen to resemble a roundish mass of semi-transparent jelly, altogether devoid of life. Soon; however, the animal begins to push out in various directions portions of the gelatinous mass of which it consists, and by the alternate expansion and retraction of these pro longations it effects a slow and somewhat irregular locomotion. Should these processes come in contact with anything fit for food, they grasp it and coalesce around it, and the morsel soon becomes inclosed in the interior of the body-. much as (to use an illustration employed by prof. Greene in his Manual of the Protozoa) a stone niarbe forced into the interior of a lump of clay, or similar plastic material. When all that is nourishing is absorbed, the indigestible remains are ejected through some part of the body. A nucleus may generally he observed, and at times (but not permanently) one or more clear vesicles may he noticed, containing a fluid which is apparently furnished during the process of digestion. The members of the genus amoba (eontaining at least three species) may be
regarded as representing the simplest forms of animal life. Closely allied to the amteba is the artinophrys, or sun-animalcule, and both these genera are completely naked. In difflught the "sarcode" is invested with a membranous oval coat with an aperture at one end, from which the pseudopodia project. In aseella the sort parts arc protected by a discoid or hemispherical shield, open below; while in the foruminitera (q.v.), the soft part is invested with a calcareous shell, which is sometimes simple, but more commonly consists of an agglomeration of minute chambers.
Various classifications of the rhiizopods have been proposed by different zoologists. That of Greene, in which they arc simply divided into annebea and pmfaiinvArti, is suf ficient for all practical purposos. All the anuebea are microscopic, and seldom exceed of an inch in diameter. The foraminifera (q.v.) are somewhat larger.
Among the most important contributions to our knowledge, of this department of the animal kingdom must be mentioned: Schultze, Ueber den Oiyanisinu.q der Polythala mien. 1854: Williamson, On the Recent Forantinifera of Great Britain, 1858; Claparede et Lachman, Etudes cur lee Infusaires et lee Ilhizopodes, 1858-00: Carpenter, introduction to the Study of the Foraminifera, 1861; and Mickel, Die Radintarien, 1862.