The two contending theories of chromosome movement differ, principally, in the location of the motor that powers this motion: Is the motor at the kinetochore or is it instead distributed, in the form of "traction fibers", along the kinetochore fiber that connects the kinetochore to the pole? Dynamic mathematical models are developed for these two opposing theories in the relatively simple case of mono-oriented chromosomes. These models are then compared relative to their quality of fit to some available data concerning the X-chromosome of the grasshopper Melanoplus differentialis. Also, the traction fiber theory is used to predict the positions obtained by bi-oriented bivalents and trivalents at metaphase equilibrium.