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In today’s rather short episode, we talk about the first creatures to have developed a centralized nervous system, though not a central nervous system as of yet. It was a simple worm like creature, with a nerve cord running along the length of its body, and an extra-large bundle of nerves toward its mouth. For worms and other invertebrate animals, like crabs, lobsters, octopuses, squid, slugs and snails, the nerve cord runs along the belly of the creature. For what would become vertebrates, including us, the main nerve cord runs along the back. Apparently, for reasons unknown, some of the worms flipped over, and decided to live their lives upside-down.
This month has included some unusually long episodes. To leave room for the upcoming Halloween special, this and the next couple of episodes are unusually short. Check back on the 31st for, “Be Afraid.: when reason can get you killed.”