"The motif ... is the germ of the famous tritone motif in the Fourth Symphony, the two halves of the motif being separated by a whole tone. "
All notes are there. S-motif is varied in countless ways. This variation seems to be difficult to see. "Normal" form would here be C-D-E-D. Step up( first half)=C-D, step down(second half)=E-D.
Now the second half is one whole tone higher(E-D becomes F sharp-E)
So, result C-D(1st half)-F sharp-E(2nd half).