What Is It? #15

OK, by now regular readers should have gotten the idea that we take lots of pictures of diatoms - after all, that's what the microscope was purchased for! But don't let that fact lead you astray with this month's quiz. Just what the heck is this thing?

A. A spore (resting stage) of a common local diatom

B. A reproductive stage of a common local diatom

C. Not a diatom at all, but a pollen grain

D. Nothing to do with plants at all, it's a stinging cell from a jellyfish

E. The world's smallest, craziest party hat