Chromosome motion in glycerol‐isolated mitotic apparatus (MA) of sea urchin and starfish eggs was investigated with respect to nucleotide specificity and the effects of antisera against tryptic fragment (Fragment A) of flagellar dynein and starfish egg myosin. The motion was highly specific for ATP. GTP, ITP, CTP, UTP, and ADP caused no displacement of the chromosomes towards the poles. The anti‐Fragment A serum completely inhibited chromosome motion in the MA of the sea urchin egg, while antiserum against starfish egg myosin as well as its γ‐globulin fraction did not inhibit the motion in the isolated MA of the starfish egg, suggesting that chromosome motion depends upon dynein‐microtubule but not upon myosin‐actin interaction. In addition, colchicine completely suppressed the chromosome motion in vitro.