Ethernet: The Definitive Guide

Colophon

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The animal on the cover of Ethernet: The Definitive Guide is an octopus. The octopus is a member of the class Cephalopoda, which also includes squid, cuttlefish, and nautili. However, unlike other cephalopods, the octopus’s shell is entirely absent. Species of octopus vary in size from under an inch (the Californian Octopus micropyrsus) to thirty feet in length (the North Pacific Octopus dofleini). Like their squid cousins, the octopus can release a noxious ink when disturbed. Octopi vary in color from pinkish to brown, but are able to change their pigment when threatened using special pigment cells called chromatophores.

Octopi catch their prey-primarily crabs, lobsters, and other smaller sea creatures-with their suckered tentacles. Many species are aided by a poison these sucker cups secrete; one Australian species’ venom is so potent that it can be deadly to humans.

Octopi are considered to be the most intelligent invertebrate species. They have both short- and long-term memory, and have shown trial-and-error learning skills, retaining the problem-solving gained through experience. Their sucker cups are very sensitive; a sightless octopus can differentiate between various shapes and sizes of objects as well as a sighted one.

David ...