THE ORIGIN AND DEVELOPMENT OF THOUGHT OF BIOMIGRATION

The idea of biomigration was first proposed by Darwin (1859).He considered that any one species of organisms had only a single center of creation.So far as the environment allows it would migrate from the center to areas as far as possible. Adams' concept of center of dispersal (1902), Matthew's theory of new center-old margin (1915), Willis' age-area hypothesis (1922) represented discussions on the idea of biomigration in those days. But after Buckman's plane of migration came out (1922), the point of view that migration was unknowable cast a shadow on the field of science. From then on the study of biomigration had been almost at a standstill for nearly fifty years. During the date shrouded in Buckman's mist, J.S. Lee (1927, 1928) was one of few men who still held Darwin's idea of migration. More and more facts showed the vitality of Darwin's idea. Frequent occurrences of fossil diachronism and a wealth of new biogeographical materials made people throw gradually off the shackle of the unknowabilitism of biomigration. Especially since the eighties a new upsurge of investigation into biomigration has been started owing to new requirements of the studies of the crustal movement, continental drift, marine transgression and regression theories.The feasible ways to explore biomigration can be provided by ① geographical tracing of the lowest horizons;② geographical tracing of the evolutionary sequences;③tracing of the corresponding habitats.Migration, as evolution, keeps going at all times under all pervading action of the Darwin's constraint.It is better to look upon migration as a kind of chance given by habitat than as a kind of ability of biota itself. Migration has created and is maintaining natural ecosystem.The studies of migration will grow into.a new branch of palaeobiogeograplly-biomigratology. Geomechanics has emerged and gone on all along with the thought of bioa migration.Its founder J. S. Lee (1927, 1928)had noted the migration of biota following the regular movement of the seawater toward and away from the equator.There must be some connection between the biota migration and the seawater movement, and this was hinted as changes of climate by J. S. Lee (1962). They may originate from a common cause-change of the rate of the earth's rotation.