Just as bears represent the pinnacle of vertebrate evolution, cephalopods (squid and octopi and such) are the very height of invertebrate evolution. I know we tend to think of them as squishy tentacle monsters, but really they are quite astonishing animals, with a surprisingly high level of intelligence. Alien, tentacled, squishy intelligence of the unfathomable depths, maybe, but intelligence nonetheless. Check out this footage of a Dana octopus squid with glowing arms. Pretty freaking cool. If you can't see the video, the National Geographic news article about it can be found here.