Bechara Kachar had shown that membranes in a cell free extract of the algae Nitella move along actin filaments. Kachar and Reese then showed that it is the ER that moves along the cortical actin cables in the intact Nitella. These are movements are at a rate of about 50 microns per second. The idea was that similar movements were going on in the axon and were the basis for slow axonal transport.