  We first include a result of the second author showing that the Banach space
S is complementably minimal. We then show that every block sequence of the unit
vector basis of S has a subsequence which spans a space isomorphic to its
square. By the Pe{\l}czy\'nski decomposition method it follows that every basic
sequence in S which spans a space complemented in S has a subsequence which
spans a space isomorphic to S (i.e. S is a subsequentially prime space).
