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SYMBIOSIS 207 SYMBOLICS Apart from lichens, the partnership of unicellular algae with raidiolarians is the best-known case of symbiosis. The partner algae — known for a long time as "yellow cells" — used to be variously inter- preted as reproductive cells, secretory cells, resex've stores, parasites, and so on ; but the researches of Geddes, Brandt, and others demonstrate their algoid and truly symbiotic nature. They have a cellulose wall (except in the Acanthomet- ridss among radiolarians), a nucleus, two pigments, of which one is at least closely analogous to the ordinary chlorophyll of plants ; they are able to live and multiply after removal from their host or after its death; in sunlight they evolve oxygen and form starch; they multiply as do free unicellular algae. From his experi- ments Geddes inferred that the starch formed by the algae may be absorbed by the radiolarians; that when they die the algae are digested by their partners ; that during life they absorb carbonic acid and nitrogenous waste from the radiolarians and in turn liberate oxygen which may accelerate the vital functions of their bearers. It seems that the partnership is distinctly advantageous, for the algae flourish and multiply, and those radiolar- ians which are without algae are few and much less common than the vast ma- jority which exhibit symbiosis. Brandt's results are for the most part in agree- ment with those of Geddes, though diver- gent on some points of details. The algae may belong to a distinct genus {Zooxan- thella of Brandt, Philozoon of Geddes), or may be simply the swarmspores of various olive-green seaweeds. Similar symbiotic algae occur in some ForaTTiinifers, in several Coslenterates, especially otherwise colorless sea ane- mones, and, according to Geddes, in some species of the Turbellarian Con- voluta. Brandt maintains that in the fresh-water sponge and in the fresh-wa- ter hydra there are symbiotic algae of the genus Zoochlorella, but Ray Lankes- ter has shown to the satisfaction of most naturalists that the pigmented bodies in those animals are no more symbiotic al- ga; than are green corpuscles in the leaf of a buttercup. Many marine sponges are infested by various kinds of algae, but we do not know that they exhibit any real symbiosis. In regard to some green protozoa there is much dispute whether the green color is due to chlorophyll bodies or to sym- biotic algae. Some forms — e. g., Stentor polymorphus, Coleps viridis, Ophrydium viride, and Vorticella chlorostigma — also occur in a colorless state. Geza Entz re- gards the bodies as algae, Miss Salitt as chlorophyll corpuscles. Famintzin finds Zoochlorellss in species of Paramascium, Stentor, and Stylonichia, which he re- gards as symbiotic forms of the Protoc- occus-like Chlorella which he and Beyer- inck have discovered living freely. Thus it appears that, while many cases of sym- biosis are indubitable, there are other cases in regard to which judgment must be for a time suspended. SYMBOL, that which specially distin- guishes one regarded in a particular character, or as occupying a particular office, and fulfilling its duties; a figure marking the individuality of some being or thing; as, a trident is the symbol of Neptune. In chemistry, an abbreviation of the name of an elementary body : thus C for carbon, H, hydrodgen, P, phosphor- ous, etc. When two or more of the names begin with the same letter, a second let- ter is added to the sjrmbol of one of these elements for the sake of distinc- tion: thus Cl=chlorine, Hg=hydrargy- rum (mercury), Pb=plumbum (lead), etc. The symbol also represents a defi- nite quantity of the element: thus H always=one part by weight of hydro- den, Hg=200 parts of mercury. In the- ology, a primitive name for the Creed, often occurring in the works of the early fathers. Also sometimes applied to the elements in the Sacrament of the Euch- arist. Mathematical symbols are of four kinds: (1) Those which stand for quantities; such as letters standing for numbers, time, space, or any of the geometrical magnitudes. (2) Those of relation, as the signs, =, > , : : : :, etc., which indicate respectively, the rela- tions of equality, inequality, proportion, etc. (3) Those of abbreviation, as."., for "hence," '.', for "because"; exponents and coefficients are likewise symbols of abbreviation, the symbol consisting in the manner of writing these numbers. (4) Symbols of operation, or those employed to denote an operation to be performed, or a process to be followed; such are the symbols of algebra and the differential and integral calculus, etc., which do not come under the preceding heads. Those of the third class are generally regarded as symbols of operation. Symbols of op- eration are of two kinds: (1) Those which indicate invariable processes, and are, in all cases, susceptible of uniform interpretations. This kind includes most of what are usually called the signs of algebra, as +, — , X, ^, V. (2) Those which indicate general methods of pro- ceeding without reference to the nature of the quantity to be operated on. SYMBOLICS, a theological term for the study of creeds and confessions of faith, etc., from the ancient meaning of