The octopus is interesting for a number of other reasons as well; not the least of which are its striking reproduction methods. In order to fertilize the female octopuses thousands of eggs, the male uses a special arm called a hectocotylus to insert small packets of sperm (called spermatophores) inside the female's mantle cavity. A few months, perhaps as few as two months later, the male octopus dies. The female, depending on the species, may keep the sperm inside her for several weeks, until her eggs are mature, then allow them to be fertilized. Once they are fertilized, she may hang them in long glistening strands from a special niche chosen for the purpose, or attach them to convenient rocks or coral, depending on her species. For a month or more, she will stay near her eggs, redirecting water over them to make sure they all receive enough oxygen while they mature. She doesn't eat while she's guarding her eggs, except for the species that reabsorb one of their arms. By the time the eggs hatch, she is too weak to defend herself, and falls victim to a predator, or she simply starves. Depending on the species, octopus may live for two to five years.
Once they hatch, looking like drifting sparkling barely visible ovoids (until you see them magnified, at which point they look like miniature octopuses), the larval octopus swim in search of planton, swimming and dining inside a cloud of plankton and other larval stage animals, often consumed themselves by the many species who dine on plankton, until they grow enough to swim deeper, and fish for real prey.
This video shows the mother encouraging the hatchlings to break free, of the egg casing and swim away. The mother was put on exhibit at the California Academy of Sciences Steinhart Aquarium. She almost immediately became enamored of a glass bottle that had been placed in her tube, and soon after, began laying eggs under a convenient rocky overhang. Shortly thereafter, mom died, leaving the tank's caretaker Richard Ross responsible for thousands of baby octopus of the Caribbean Octopus vulgaris species. Ross took the video below, as well as the stills you can see here, showing the laval babies.
Where I live, in coastal Washington, you can occasionally find baby octopuses, about the size of a quarter up to a silver dollar, in tidepools. You can see a picture of one here, and some more images here.
Image Credit: Minette Layne