Before revision:  Revealed by  spindle rocking, these pulling forces are regulated by the force generator dynamics, which are related to mitosis progression. This may be combined with a second regulation, this one by the posterior spindle pole position, which can be seen when comparing related species. Results: After delaying anaphase onset, we identified a positional pulling force regulation in C. elegans, which we ascribed to microtubule dynamics at the cortex.
After revision:  Revealed by spindle rocking, these pulling forces are regulated by the force generator dynamics, which are in turn consequent of mitotic progression. We found a novel, additional, regulation of these forces by the spindle position. It controls astral microtubule availability at the cortex, on which the active force generators can pull. Importantly, this positional control relies on the polarity dependent LET-99 cortical band, which restricts or concentrates generators to a posterior crescent. We ascribed this control to the microtubule dynamics at the cortex.