The male octopus has a modified arm called the hectocotylus, which is about a meter long and holds rows of sperm. Depending on the species, he will either approach a receptive female and insert the arm into her oviduct or take off the arm and give it to her to store in her mantle for later. In the latter scenario, the female keeps the arm until she lays her eggs, at which time she takes the arm out and spreads the sperm over her eggs to fertilize them.
The female meticulously cares for her eggs until they hatch, forgoing food the entire time. She blows currents across the eggs to keep them clean and protects them from predators. The eggs might incubate anywhere from two to 10 months, depending on the species and the water temperature. Once they hatch, they're on their own -- one source cites an estimated 1 percent survival rate for the giant Pacific octopus from hatchling to 10 millimeters. Depending on the species, some octopuses begin life as miniscule specks floating on the ocean's surface that drift down upon reaching a larger size, while some start out a bit bigger on the ocean's bottom. Little else is known about the early lives of octopuses