The "grey swirly things" are cross-sections through the rhabdoms of
the eye. From the longitudinal section
view, you can see that these rhabdoms are cylindrical structures. As
you can see from the close-up view,
the rhabdoms themselves are made up of tightly packed cylindrical structures;
these are finger-like extensions from the cells which make up the retina
of the eye. Thus each rhabdom is packed with membranes containing the photo-sensitive
pigments which the eye needs for its functioning.
More details are provided in the Opiliones Notes.