CLASS B. Ruizororm (q.v.). Protozoa having the power of throwing out and retract ing prolongations (pseudopodia) of the body substance; no mouth, with few exceptions. Divided into five orders: Order I. ..lIonera (Gr. mows, unit). "Mina!,e organisms having the power of throw ing thread-like prolongations, which are a part of the structureless body (sarcod,:). These pseudopodia branch out in all directions, interlacing and anastomosing. When at rest the body is more or less globular. There is no nucleus or contractile vesicle.
Order II. Amcebea (Gr. amoibos, changing). Rhizopods which are usually naked, having short, blunt pseudopodia which do not anastomose. They contain a nucleus and one or more contractile vesicles. The aniceba or protons animalcule is the type of the order. It is a microscopic animal, which makes its appearance in vegetable fresh-water infusions. It is composed of two layers of gelatinous matter, called the entosarc and the endosarc, or outer and inner layers. The endosarc contains the nucleus and contrac tile vesicle or vesicles', and also cavities called vacuoles. There are no traces of any nervous system in the amceba, and yet it possesses locomotive power.
Order III. Foraminifera (Lat. foramen, an aperture). Rhizopods in which the body is protected by a shell or test, usually composed of carbonate of lime. Body not divided into eutosarc and endosarc, as in ammba; and there is neither nucleus nor contractile vesicle. Pseudopodia long, thread-like, and interlacing. The foraminifera are mostly marine. Dr. Carpenter says that foraminiferous fauna probably have a greater modern. range of seas than at any previous period, but there is no indication of any tendency to elevation to a higher type. There are vast deposits of them in the deeper portions of the Atlantic ocean, where the water is warmed by heated currents. There are several
genera and species, many of them presenting rarely beautiful forms. Foraminifera have been found in paleozoic and mesozoic formations, and the eozoon Conadense, found in the Laurentian rocks of Canada, has been thought to be a gigantic foraminifer. See FORA• 3IINIFERA.
Order IV. Radiolaria (Lat. radius). Rhizopods having a siliceous shell or test, or siliceous spicules, and pseudopodia standing out like radiating filaments, sometimes interlacing. There are three families.
Family 1. Acantitrometrina, minute globular bodies, surrounded by siliceous. radiat ing spines, often floating near the surface of the ocean, sometimes in great numbers.
Family 2. Polycietina. Nearly related to foraminifera, the principal difference being that the shells are flinty instead of calcareous. The siliceous shell is sometimes exceed ingly beautiful. They arc all microscopic, and have a wide distribution in the ocean. They arc also abundant tertiary fossils.
kamily 3. Thalanicollida (Gr. tladassa, sea, and 1,w/7a, glue). Rhizopods having "structurcless cysts containing cellular elements and sareode, and surrounded by a layer of sarcode, giving off pseudopodia, which commonly stand out like rays. but some times have the form of a network" (Huxley). They are simple, or composite. The three best known genera of the family are eplarrozoun, co/./9sphfera, and llut/a&ac.9/1a. They abound iu most seas, floating near the surface; size, from an inch in diameter down wards.
Order Spongida or Porifera (q.v.). "Sarcode bodies destitute of a mouth, and united into a composite mass which is traversed by canals opening on the surface, and is almost always supported by a frame-work of horny fibers, or of siliceous or calcare ous spicula" (Allman). Sec broNGE.