Planaria can also regenerate themselves; you can slice a Planarian into as many as 279 pieces, and each piece will regenerate a whole new individual. Apparently, though, slicing it in 280 pieces won't work. Think of all the time someone spent slicing Planaria to make this discovery.
Some Planaria have eye spots that give them a cross-eyed appearance to humans, but Planaria can't do anything more with them than detect the intensity of light, so they don't look a bit silly to each other. The eye-spots led to a very interesting couple of experiments. Robert Thompson and James McConnell showed Planaria a bright light and then gave them an electric shock. Pretty soon, the Planaria would react the same way to the bright light that they did to an electric shock. For a Planarian, this is pretty intelligent. So they cut the Planarian in half, and then they had two Planaria who were terrified of lights. This is progress.
McConnell was understandably excited by these results, so he took it a step further. He ground up some of his star pupils from earlier experiments and fed them to other Planaria. How he came up with this idea is a mystery. Anyway, he reported that Planaria who'd eaten a meal of chopped-up pre-trained Planaria, learned to be afraid of bright lights faster than Planaria who ate ordinary Planaria kibble. (How much faster, I don't know, but probably not that much, considering they were Planaria.)
For a while, scientists everywhere were repeating the experiment, feeding fish-brains from trained fish to other fish, trained-mice-brains to other mice, and so forth, and there was a lot of hope this would have applications for humans. It turned out though, McConnell's results were invalid; eating the brains of even the smartest Planarian on the planet won't raise the IQ of another Planarian one iota. McConnell was only seeing what he wanted to see. Why he wanted to see it is another question altogether.
When you get down to it, the difference between the brightest and the stupidest Planarian is not that great, nor between the best-looking and the ugliest. The truth is, even the biggest fans of Planaria, and how many of those do you run across, would have enormous difficulty telling one from another. A video in a Wikipedia article is just titled, "Unidentified Planarian." I'm sure, however, that Planaria think very highly of themselves, and that among Planaria there are some cool ones and some that you wouldn't want to be associated with, and they all go around making restrained boasts about how they're not parasites like some other flatworms they could mention and whenever they hear gossip about some parasite, they shudder and say, "How awful!"
