Sentence:  Like in action where one should execute the movements or responses one at a time (and it is physically impossible to do it otherwise, circus practices notwithstanding), <WSD>microgenesis</WSD> tends to solve one or another subtask at different stages of its unfolding. In high-level activity, particular efferent operations often unfold as more or less arbitrary segments in a continuous flow of actions. [...] Can you tell the exact moment when a ball-toss ends and the strike for the serve begins in tennis? Not so easily. Similarly, in <WSD>microgensis</WSD>, stages unfold as somewhat arbitrarily isolable epochs in a continuous flow of percept genesis. 
Meaning of the word marked with <WSD> tags:  The development, in discrete but generally imperceptible (seemingly continuous) increments, by the human body or brain, of thoughts, motions, or actions.