  In the absence of interaction it is well known that the Kogut-Susskind
regularizations of fermions in the spin and flavor basis are equivalent to each
other. In this paper we clarify the difference between the two formulations in
the presence of interaction with gauge fields. We then derive an explicit
expression of the transfer matrix in the spin basis by a unitary transformation
on that one in the flavor basis which is known. The essential key ingredient is
the explicit construction of the fermion Fock space for variables which live on
blocks. Therefore the transfer matrix generates time translations of two
lattice units.
