LAMARCKISM. The doctrine of J. B. P. A. Lamarck (q.v.). which considers the fundamental or primary factors of evolution in the trans formation of species. Lamarck claimed that all living beings arose from germs, through spon taneous generation, and that the most primitive was monad-like. In his opinion the first germs of plants and animals were formed in favorable places and under favorable circumstances. The functions of life beginning and an organic move ment established. these germs "necessarily grad ually developed the organs, so that after a time and under suitable circumstances they have been differentiated" into parts or organs, develop ment proceeding from the simple to the com plex. Ile postulated great length of time, so great "that it is absolutely beyond the power of man to appreciate it in an adequate way." He adds that "with the aid of sufficient time, of eir cumstanees which have been necessarily favor able, of changes of condition that every part of the earth's surface has successively undergone— in a word, by the power which new situations and new habits have of modifying the organs of living beings—all those which now exist have been gradually formed such as we now see them." Vestigial organs are explained as remains of parts which had been actively used by the an cestors of existing, forms, but which have be come atrophied by disuse. The fact of is fully appreciated, as also adaptation to needs. ln his opinion specific characters vary most. He points omit that the peripheral parts. as the leg.;, mouth-parts, antenna., etc.. are first affected by the causes which produce variations, while it requires a longer time for variation in the in ternal organs to bike place. He also insisted that when the conditions of existence remain constant, species do not vary.
Lamarck's factors of organic evolution were seven, as follows: (1) Effects of favorable cir cumstances due to changes of environment. of climate, soil, food, temperature, etc. Such changes are direct in the case of plants and the lowest animals, but indirect in the ease of the higher animals and man.
(2) Needs, new physical wants or necessities induced by change of the conditions of life, result in the production of new propensities, new habits and functions. Lamarck showed that change of
habits may lead to the origination or modifica tion of organs; that changes of functions also modify or create new organs. Ile *aid: "It is easy to demonstrate by observation that uses or habits have given rise to forms," which is an other expression for Ceoffroy Saint-Hilaire's "C'est in function qui er6e l'organ," and an an ticipation of Dohrns principle of change of func tion as a means of modification of organs. (See FUNCTION-CHANGE.) La taa rek'S use of the word need or necessity (bcsoin) has been greatly mis understood and caricatured. He shows, however, that by change of environment animals arc sub jected to new surroundings. involving new ways and means of living. Thus certain land birds driven by necessity (besoin) to obtain their food in the water, gradually assumed characters, or structures, adapting them for swimming, wad ing. or for searching for food in the shallow water, as in the ease of the long-necked kinds.
(3) Use and disuse. The continual use or ex ercise of organs develops them, as in the wings of birds, etc. The second of these principles he illustrates by the eases of the mole, the whale bone whales, whose rudimentary teeth exist in the embryo, the ant-eater, the blind Proteus of eaves. the eyeless bivalves, and the snakes, whose ancestors lost their limbs in the process of be coming adapted for gliding through brush or grass or similar obstacles.
(4) The doctrine of the struggle for existence and of competition was stated by Lainarek. He frequently refers to the precautions that nature has taken to place limits to the too great increase in individuals, and the consequent overcrowd ing, of the earth. The stronger and better armed, he says. devour the weak, the large animals de vour the smaller. The multiplication of the smaller species is so rapid that thew smaller species render the earth inhabitable for others, but their length of life is very short, and nature always preserves them in just proportions not only for their own preservation, but also for that of other species. The larger species, however. multiply slowly, and thus is preserved the kind of equilibrium which should exist.