It usually begins with the male octopus poking the female with his long, flexible, hectocotylus arm and then slipping it into her mantle cavity.
Once the sperm packet has been deposited, the female retires to her den and lays tens of thousands of eggs, which she weaves into strings and attaches to the roof of her underwater dwelling. She keeps the eggs clean by blowing jets of water on them and is unable to leave her den to forage for food during this time.
After about a month, the eggs hatch and the weakened mother octopus dies. The father also dies within a few months of mating, leaving the newborns to fend for themselves.
[Tomado de "Study sheds light on octopus sex", The Guardian, 3 de abril de 2008]
Así los pulpos, así las cosas.