The rates at which molecular sequences may deposit onto growing lamellae in a crystallising polyethylene melt are examined on the basis of the results of recent self-diffusion experiments in such melts, in conjunction with theories of molecular dynamics in polymer melts based on the reptation picture. The results are compared with rates of sequence deposition in polyethylene melts as estimated from experimentally measured growth rates. This comparison indicates that, purely from a kinetic point of view, some regular folding of molecular trajectories at lamellar surfaces is not incompatible with experiment.