No amoeba, but I'll take what turned up:
It's a very small snail, bottom side up, seen here through a 20X objective (field diameter 0.8 mm). The shell was transparent, and to my considerable surprise, it was easy to see the little critter's heart beating inside.
This animated gif hardly does justice to the action. See the movies instead: whole snail (1MB, wmv) and closeup of heart (1.5MB, wmv).
There is a brief description of snails very much like this one here. The heart is two-chambered -- one auricle, one ventricle.
--Rik
All images using Canon SD 700 IS movie mode, through eyepiece of microscope. Closeup of heart was shot by optically zooming the camera, same microscope settings.
I noticed in the first one, that there is a small, rather translucent object that crops up just between the left corner and center area. There are actually two of them but it is the first one that has me curious. The first object to appear, seems to be pulled in to the area of the heart as it is beating. What was that? 
