The deer is a symbol of speed in the spiritual progress.
The Adhar has to be steadily prepared, changed, made fit for the supramental Descent. There are several powers between the ordinary mind and the supramental and these must be opened up and absorbed by the consciousness — only then is the supramental change possible.
The question arose and always arises because of an eagerness in the vital to take any stage of strong experience as the final stage, even to take it for the overmind, supermind, full Siddhi. The supermind or the overmind either is not so easy to reach as that, even on the side of the Knowledge or inner experience only. What you are experiencing belongs to the spiritualised and liberated mind. At this stage there may be intimations from the higher mind levels, but these intimations are merely isolated experiences, not a full change of consciousness. The supermind is not part of mind or a higher level of mind -- it is something entirely different. No sadhak can reach the supermind by his own efforts and the effort to do it by personal tapasya has been the source of many mishaps. One has to go quietly stage by stage until the being is ready and even then it is only the Grace that can bring the real supramental change.
As if in her ascent to her lost source
She hoped to unroll all that could ever be,
Her high procession moves from stage to stage,
A process march from form to ampler form,
A caravan of the inexhaustible
Formations of a boundless Thought and Force.