Some background. I found him, let's call him Bruno, I found Bruno "inside" the gelatinous mass of snail eggs I was photographing, but outside the individual eggs. He is roughly 300µm long, moves exceedingly slow, can't change shape too much, any more than a snail could, looks like he has vacuoles that evacuate, [see video], has cilia around his head/nose/mouth, has no snail eyestalks, seems to have a digestive tract. It looks like he was crawling on the bottom side of the coverslip, [see video], but that's not possible, as he was inside the gelatinous mass of the egg case.
My guess is, he is a snail parasite, which I know they are loaded with. Other guesses are an amoeba, baby snail, ciliate of some kind. I hope someone can positively ID him.
Video of Bruno.
A comparison of Bruno to one of the snail eggs. Bruno is just to the North of the bottom egg. 4x.
A full frame shot at 10x.
A crop at 10x. It's not grainy, that is the gelatin of the surrounding egg sac, with Bruno, a Vorticella and other assorted opportunists.
20x full frame.
