Well reasoned, and not so far off.rjlittlefield wrote:There has to be some structure to the eyespot, or it would not provide direction. One possibility is a lump of units that are individually non-directional, but dense enough to shadow units on the side away from the light. I wonder if that's how it actually works?
--Rik

Fabulous image! It might be Euglena mutabilis (a very changeable species, as the name suggests). It is certainly not the relatively stiff E. acus (which is a Lepocinclis, in any case).