This is the third in the series of images of some of the organisms found in just a few drops of water collected from a pond in a disused quarry on the edge of the moors in Weardale
This little object (which I think may be a species of Peridinium), a mere five one hundredths of a millimetre across, is a dinoflagellate - a single-celled, hardshelled organism that's powered by two rapidly undulating flagellae. One runs on the horizontal groove around the 'equator' of the example you can see here. The other runs in vertical groove, extending from the equator to the apex - it's out of sight on the distal side of this image, although you can just see the apex of the vertical groove at the top. It seems like an unlikely means of motive power but it works - this one whizzed all over the slide before it paused for long enough for me to get a photograph.
This is the empty shell of a dead dinoflagellate, which reveals the intricate pattern on the armoured surface composed of cellulose plates. Unfortunately....
....it wasn't intact - you can see where about a quarter of the sphere has broken away, but you can also see the equatorial flagellar groove rather nicely. The green object approrach from lower right is a diatom, which is just about to punt the diatom out of the way as it glides past.
For some fascinating recent research on dinoflageelates, take a look at this post about a predatory dinoflagellate at Jennifer Frazer's The Artful Amoeba web site, where you can read about their amazing biology and also find links to drawings and electron micrographs that show the organism rather more clearly than my photographs.
Coming next: An assortment of protists