Any question as to prematureness of a final rejection should be raised, if at all, while the application is still pending before the primary examiner. This is purely a question of practice, wholly distinct from the tenability of the rejection. It may therefore not be advanced as a ground for appeal, or made the basis of complaint before the Patent Trial and Appeal Board. It is reviewable by petition under 37 CFR 1.181. See MPEP § 1002.02(c).