It is a special feature of cell aggregation in the developing nervous system that in most regions of the brain the cells not only adhere to one another and also adopt some preferential orientation.

This question tests parallel structure and correct conjunction use. The sentence structure 'not only...but also' requires parallel verb forms. Option D correctly provides 'to one another but also adopt' - both infinitive verbs ('adhere' and 'adopt') are in base form, creating proper parallel structure. Option A uses 'to one another and also adopt' which is acceptable but less precise. Options B and C incorrectly use 'one to the other' and introduce inconsistent verb forms, disrupting the parallel structure required by 'not only...but also'.