Gurudev, in the Ashtada Prakruti (referring to the eight materialistic forms of the Lord’s divine energies – Earth, Water, Fire, Air, Space, Mind, Intellect, Ego), the ego has been counted among one of them, but not the Chitta (memory). Why is this so?
You can count it in then!
Different rishis have elaborated different principles and ways of understanding the various levels of existence. You can see the mind, intellect and the ego as the three extensions of memory. These are simply four different functions or behaviours of one Consciousness. Do not misunderstand these as limited to some event. They are the four different expressions of one Consciousness.
Some schools of thought count only three of these and not all four. They consider memory to be an integral part of the mind or the intellect and hence do not count it separately.