page 3, full paragraph 3.
Keiko Nomura pointed out that the following statement is false:
"Thus slender particles resembling needles and rectangular parcels
maintain their initial orientation."
This statement is indeed inaccurate. The correct statement is:
"The average rate of rotation of two perpendicular slender particles
centered at a point, is equal to zero. As a consequence, the rate of rotation
of slender partciles passing through a point, averaged over all possible
orientations, is equal to zero; and by extension, the rate of rotation
of rectangular parcels averaged over all orientations, also vanishes. "
An illuminating discussion of the relationship between the vorticity
and the rate of rotation of infinitesimal or finite fluid parcels is given
by: J. A. Shercliff, 1975, A note on vorticity, J. Inst. Maths. Applics.