If you ever see two octopuses apparently holding hands, it probably means that they are mating. The male pumps spermatophores down a specially modified tentacle called the hectocotylus to fertilise the female's eggs.
This can take up to an hour. For about a week afterwards, the female lays clusters of up to 200,000 grape-like eggs inside her nest. She then guards them for four to eight weeks, depending on water temperature, continually touching and cleaning them as she circulates fresh water over them. The eggs hatch into larvae, which look like tiny adults, but which are only 3mm in length. These float in the sea with plankton before coming to rest on the seabed. They grow to maturity in about two years. In the meantime, their mother may well have died from exhaustion, as many female octopuses never recover their strength after going six weeks without food whilst guarding their eggs.