EVOLUTION. 334 EVOLUTION. Augustine's view. But the idea of special creation became the universal teaching i*rom the middle of the sixteenth to the middle of the nineteenth century. That broad-minded early German philosopher Leibnitz (1646-1716) gave examples of the gra- dation of characters between living and extinct forms as proofs of the universal gradation or connection between species. He believed in a chain of being, and that the different classes of animals are so closely united that there are no gaps between them. He also suggested that by means of great changes of habitat 'even the species of animals are often changed;' he also taught the doctrine of the continuity of nature, and was the author of the sa-ing, Natura non facit saltum. Buffon (1707-88) thoroughly read and was in- fluenced by Leibnitz's writings. Whether or not he owed his evolutional views to Leibnitz, he stated, and as frequently denied, the mutability of species. He suggested that such changes wero directly produced by changes in climate, food, and domestication, and he gave a few examples of the effects of disuse, and held that all ani- mals were possibly derived from a single type. A stronger, more observant and bolder reasoner than Buffon was Erasmus Darwin (q.v. ), the grandfather of Charles Darwin. He was a country doctor, not a working naturalist, but a remarkably close observer, and a sound thinker. He claimed that all animals were derived from 'a single filament,' insisted on the effects of changes of climate, of use, characters being pro- duced by the exertion of animals. He was the first to propose the factor of sexual selection, stated the principle of the law of battle, quite fully elaborated the idea of protective mimicry, and vaguely stated the doctrine of use- inherit- ance. The true founder of evolution, however, was Lamarck (q.v. ), who was the leading zoologist of the period between Linnaeus and Cuvier (1744- 1829). In 1801 he first published his evolutionist views, He taught in his lectures (1801-1806), and in his Philosophic zoologique (Paris, 1809), I Ik. I all organisms arose from germs; that de- velopment was from the simple to the eo?nplcx ; that the animal series was not continuous, but tree-like; and he constructed the first phylogenet- io tree. The Lamarckian factors are the changes of environment, climate, soil, food, and tempera- ture, such changes being direct in plants and the lowest animals, indirect in the higher animals, lie speaks of the struggle for existence, stating that Hie stronger devour Hie weaker, and refers to competition. He discussed at length the effects of use and disuse, taught that vestigial struct ores are the remains of organs actively used by the ancestors of existing forms, and claimed that new wants or necessities induced by changes of climate, habitat, etc., result in the pro- duction of new propensities, new habits, and new functions. Change of habits, he says, originate organs, change of functions create new organs, inn! tlic formation oi new habit» precedes the origin of new organs or modification of organs already formed. He refers to the sti amping effects of cro ing, and to isolation as a factor. His definition of species is the most satisfactory yet I imarck's views were not generally ac- cepted, bul i ni I'll or ignored, largely through the influence of Cuvier and his disciples. See Lamabckism; Neolamarckism. Notwithstanding this history, it was reserved for Charles Darwin, in 1859, seconded by A. R. Wallace, to convert the scientific world to evo- lutional views. The new theory he specially advocated was that of natural selection. Darwin claimed that there was a universal tendency of fortuitous variation; its causes, he thought, were only in part known. He showed that favor- able variations were preserved, and that natural selection has a directive force. He dwelt con- vincingly on the facts of competition, of the struggle for existence, and on the biological en- vironment. At the same time his Origin of Sjiecics was a massive and irresistible argu- ment for the doctrine of descent; and as further expounded and upheld by Hooker, Huxley, Fritz iliiller, Haeckel, and others, it became generally accepted. Darwin was the prince of observers and experimenters. He was also an expert systemat- ise a clear, persuasive writer; and into what- ever field he entered his work was epoch-making. Meanwhile in England, as early as 1852, Her- bert Spencer advocated evolution from a philo- sophical point of view. He proposed the term evo- lution both for the inorganic and organic world. His broad, synthetic mind grasped the full signifi- cance of cosmic evolution, and he extended the doctrine of descent to human history, human society, morals, ethics, and religion. He is the philosopher of science, and of all that pertains to man. He has worked rather along Lamarck- ian lines, holding that natural selection as such was of secondary importance, as compared with the primary factors of organic evolution. Since Darwin's death, r under the leadership of Alfred Russel Wallace, and especially of Weis- mann, the School of Neo-Darwinism (q.v.) lias arisen. Weismann, distinguished by his great work on the embryology and metamorphism of insects, and his investigations on temperature forms, has shown that heredity has a physical basis, the chromatin being the bearer of heredity. He asserts the 'all-sufficiency' of natural selec- tion, and claims that variability is due to sexual reproduction. Literature. C. Darwin. The Origin of Spi < '<• a by Means of Natural Selection (first edition, London, 1859; sixth edition, 1371) ; Descent of Man (New York, 1S72) ; The Variation of Ani- mals and Plants Under Domestication (London, 1881); A. R. Wallace, Natural Selection (Lon- don and New York, 1870) ; Darwinism, an Ex- position of the Theory of Natural Select ion irith Some of its Applications (London, 1889) ; Eras- mus Darwin. Zoonomia, or the Laws of Organic Life ( London, 1796) ; J. P. B. A. Lamarck. Philo- sophie zoologique (Paris, 1809); T. H. Huxley, On the Origin of Species (New York. 1863) i Herbert Spencer, Principles of Biology ( London, L898; Xew York, 1900) : Factors of Organic Evo lution (Nct York, 1895); A. Hyatt. "On the Parallelism Between the Different Stages of Life in the Individual and Those in the Entire Group of the Molluscous Order Tetrabranchiata," in Memoirs Boston Society of Natural History (Boston, 1*66): denesix'of the Arietidw (Wash- ington, 1889); Phytogeny of an Acquired Char- acteristic (Philadelphia. 1894); Fritz Miiller, Fiir Darn-in (Leipzig, 1864; English translation, London. 1869) : H. Miiller, Fertilization of Flow- . , (translated bj D'Arcy W. Thompson, Hon-
