Causes of anaphasic movement are :
(a) Each chromosome fibre or tractile fibril consist of microtubules. The spindle is also formed of microtubules. The chromosome fibres may glide over the spindle fibres by (a) rachet mechanism, (b) under force developed at the poles.
(b) These are caused by contraction of chromosomes fibres.
(c) Formation and expansion of interzonal fibres.
(d) Dissolution of microtubules of chromosome fibres
at their ends.