  Having previously identified the photon field with a (special) linear
Complex, we give a brief account on identifications and reasoning so far. Then,
in order to include spinorial degrees of freedom into the Lagrangean
description, we discuss the mapping of lines to spins based on an old transfer
principle by Lie. This introduces quaternionic reps and relates to our original
group-based approach by SU(4) and SU*(4)~SL(2,H), respectively. Finally, we
discuss some related geometrical aspects in terms of (spatial) projective
geometry which point to a projective construction scheme and algebraic
geometry.
