200 years ago, an Estonian zoologist described a strange worm that lived on the skin of freshwater snails. No one knew what it was doing there, and after 200 years, the answer is that it may be a protector of the snail, that it may be a parasite, or maybe both. It is important to me because I got to know these worms in person when I did my first scientific study almost four decades ago. They looked like dozens of liquid crystal tentacles protruding from the snail.