I'd like to tell you a story.
Once upon a time, on the bottom of a sea, there was a blob.
It was a simple, one-layer blob of cells and slime, plastered on the sea-floor, slowly nabbing at the minerals underneath it and sucking in some food-stuff, floating above it.
But, one day the sea changed - strong currents started blowing around it. Many of its kin were gone, swept away but the merciless flow. But our blob didn't. It used the minerals it had been eating to build a mineral crust on its side facing the currents. The lower end of this crust went into the sea-floor, rooting the blob firmly in place. In addition, the crust had small openings in it, so that the cells that were far from other surfaces didn't starve and thirst.
The crust was quite sturdy, but the currents were cunning. They flew around the blobs protection, and even though they couldn't tear it from its place, they tugged at its rear part, making the blob stretch and get thinner.
The blob grew thing and long, but its strength remained the same and soon its rear part was all but in the power of the currents.
The currents pushed and tugged, and the roots of the blob's shield began cracking, when the strength of the currents themselves ended. Their fighting and plotting burned them quick, and the blob was left free in its new shape. In the calm water, it could see its brothers and sisters settle down and turn back into shapeless blobs. But the blob wasn't ready to let go of what it had won through such hardship. It observed its surroundings lifting its rear part up through the water.
Suddenly it felt an unfamiliar taste. It was an upper layer of water, rich in oxygen and light, blossoming with simple lifeforms. The blob found them delicious, and wanted to stay in the upper layer. But, of course, it had its lower, front part rooted in the ground. The front part couldn't taste the delicious inhabitants of the upper water layers. It would surely shrink and wither without the care of the rear part. Yet, without the front part, the blob would have fallen victim the currents were they ever to return. The rear part and the front part couldn't live without one another, and so they decided to set up strong communication in the form of several lines of vessels transporting food around the blob's body. And to efficiently maintain the lines, the body was divided into several compartments, and the cells of each compartment served only their part of the lines.
And so, for a time, the blob was safe and content...
Edit: I recently realized that on my Photobucket I called the folder I put my pictures for this project in, "Otherworldly Ar
c". I don't know how it happened, an example has always been in front of me, but... It's late to correct it now, because all the pictures would change their paths. The shame will be forever with me!
Oh. I also wanted to ask, are there really protists several centimetres in size?