Abstract: The occurence of intercellular migration of chromatin substance in the pollen mother cells is one among many important phenomena observed during meiosis, especiallythe stage when syndesis between homologous chromosomes has attracted many investigators. Years ago we have reported on this subject from various angles. At first we have described the cellular and nuclear characteristics of the migrating chromatin substsnceand then we studied the morphology and physiology of these cells in the migrating stage (Cheng et al, 1955, 1956, 1959, 1.964). Since then the source of the energy for intercellular migrating chromatin substance has been inverstigated by comparing the effects of metabolic poisons and reduced oxygen tension on respiration and migration. It has been found that both respiration and migration might be inhibited simultaneously. Based upon the results ginven in those former reports and data presented in this paper, we propose a working hypothesis on the probable mechanism of the intercellular migrating chromatin substance in the paragraph below. The streaming of karyolymph plays a prominent role in the intercellular migrating chromatin substance in the pollen mother cells, and the folding and unfolding processes of the contractile protein may furnish the motive force for the migration of chromatin through the cell wall. The source of the energy for both protoplasmicstreaming and migration of the chromatin substance is supplied by ATP (adenosinetriphosphate) which is produced in the process of aerobic respiration.