evolution (evolushon)

[= F. évolution = Sp. evolucion = Pg. evolução = It. evoluzione, The wise, as flowers, which spread at noon And all their charms expose, When evening damps and shades descend, Their evolutions close. Young , Resignation, i. The first appearance of the eye consists in the protrusion or evolution from the medullary wall of the thalamencephalon or interbrain of a vesicle. H. Gray , Anat. (ed. 1887), p. 121. Hence-2. The proce of evolving or becoming developed; an unfolding or growth from, or as if from, a germ or latent state, or from a plan; development: as, the evolution of history or of a dramatic plot. The whole evolution of ages, from everlasting to everlasting, is so collected and present i fickly represented to God at once, as if all things which ever were, are, or shall be, were at this very instant really present. Dr. H. More, Divine Dialogues. Ability to recognize and act up to this law of equal endowment of humanity-an the dowment now in proce of evolution. H. Spencer, Social Statics, p. 481. The evolution of the sickening vapours emitted by foul oxide need not be a source of annoyance, as the oxide can be revivified in the purifiers. W. R. Bowditch , Coal Gas, xi. 21. Specifically- (a) In biol .: (1) The actual formation of a part or of the whole of an organism which previously existed only as a germ or rudiment; ordinary natural growth, as of living creatures, from the germinal or embryonic to the adult or perfect state: as, the evolution of an animal from the ovum, or of a plant from the seed; the evolution of the blo om from the bud, or of the fruit from the flower; the evolution of the butterfly from the caterpillar; the evolu tion of the brain from primitive cerebral vesicles, or of the lungs from an offshoot of the intestine. (2) The release, emergence, or exclusion of an animal or a plant, or of some stage or part thereof, from any covering which contained it: as, the evolution of spores from an encysted animalcule; the evolution of a moth from the cocoon, of an insect from the wood or mud in which it lived as a larva, of a chick from the egg-shell which contained it as an embryo. The parasite is often taken for the He ian fly. Many have been deceived by the specious circumstance of its evolution from the pupa of the destroying insect. Say. (3) Descent or derivation, as of offspring from parents; the actual result of generation or procreation. As a fact, this evolution is not open to question. As a doctrine or theory of generation, it is susceptible of different interpretations. In one view, the germ actually preexists in one or the other parent, and is simply unfolded or expanded, but not actually formed, in the act of procreation. (See ovulist, sperm at ist.) This view is now generally abandoned, the current opinion being that each parent furnishes materials for or the substance of the germ, whose evolution results from the union of such elements. See epigenesis . (4) The fact or the doctrine of the derivation or descent, evolutionism with modification, of all existing species, genera, orders, cla es, etc., of animals alid plants, from a few simple forms of life, if not from one; doctrine of derivation; evolutionism. (See Darwin ism.) In this sense, evolution is opposed to creationism, or the view that all living things have been created at some time substantially as they now exist. Modern evolutionary theories, however, are le concerned with the problem of the origination of life than with questions of the ways and means by which living organisms have a umed their actual characters or forms. Phylogenetic evolution insists upon the direct derivation of of life from other antecedent forms, in no other way than as, in ontogeny, offspring are derived from parents, and consequently grades all actual affinities according to propinquity or remotene of genetic succe ion. It presumes that, as a rule, such derivation or descent, with modification, is from the more simple to the more complex forms, from low to high in organization, and from the more generalized to the more specialized in structure and function; but it also recognizes retrograde development, degeneration or degradation. The doctrine is now accepted by most biologists as a conception which most nearly coincides with the ascertained facts in the case, and which best explains observed facts, though it is held with many shades of individual opinion in this or that particular. See natural selection, under selection. Evolution, or development, is, in fact, at present employed in biology as a general name for the history of the steps by which any living being has acquired the morphological and the physiological characters which distinguish it. Huxley , Evolution in Biology. (b) In general, the pa age from unorganized simplicity to organized complexity (that is, to a nicer and more elaborate arrangement for reaching definite ends), this proce being regarded of the nature growth. Thus, the den opgent of planetary bodies from nebular or gaseous matter, and the history of the development of an individual plant or animal, or of society, are examples of evolution. Evolution is an integration of matter and concomitant di ipation of motion; during which the matter pa es from an indefinite, incoherent homogeneity to a definite, coherent heterogeneity; and during which the retained motion undergoes a parallel transformation. H. Spencer , First Principles, § 145. The hypothesis of evolution supposes that in all this vast progre ion there would be no breach of continuity, no point at which we could say, "This is a natural proce ," and, "This is not a natural proce "; but that the whole might be compared to that wonderful proce of development which may be seen going on every day under our eyes, in virtue of which there arises, out of the semi-fluid, comparatively homogeneous substance which we call an egg, the complicated organization of one of the higher animals. That, in a few words, is what is meant by the hypothesis of evolution . Huxley , Amer. Addre es, p. 10. (c) Continuous succe ion; serial development. 3. In math.: (a) In geom., the unfolding or opening of a curve, and making it describe an evolvent. The equable evolution of the periphery of a circle or other curve is such a gradual approach of the circumference to straightne that its parts do not concur and equally evolve or unbend, so that the same line becomes succe ively a smaller are of a reciprocally greater circle, till at last they change into a straight line. (b) The extraction of roots from powers: the reverse of involution (which see).-4. A turning or shifting movement; a pa ing back and forth; change and interchange of position, especially for the working out of a purpose or a plan; specifically, the movement of troops or ships of war in wheeling, countermarching, manœuvering, etc., for disposition in order of battle or in line on parade: generally in the plural, to expre the whole series of movements. These evolutions are doublings of ranks or files, countermarches, and wheelings. Harris . It is not certain whether the idiots' brains had undergone any local evolutional change as the result of education or training. H. Spencer , Inductions of Biology. The origin of life, and the conditions which have gradually given rise to organization, are e ential evolutional moments, as yet in the twilight of mere fanciful conjecture. Pop. Sci . Mo., XIII. 457.