Check out these tiny Ocotopus hatchlings at Mote Marine Laboratory & Aquarium in Florida!
Octopi reproduction is really quite interesting. Males have a specially adapted arm, called a hectocotylus, which they use to transfer sperm packets called spermatorphores into to a female's mantle cavity. Octopi lead short, solitary lives of one to two years; the pair do not remain together, and males die within a few months of mating.
A female can store the sperm in her mantle until she is ready to fertilize and lay her eggs. A female may lay hundreds of thousands of eggs, which she anchors to a hard surface in a protected den.
After eggs are laid, she devotes the rest of her life to caring for them. She will guard the eggs and keep water circulating around them so that the developing offspring receive enough oxygen. The mother stops eating after her eggs are laid, and she will die soon after they hatch.
Newly-hatched octopi are called larvae, and will develop into hatchlings or fry. The newborn octopi, though tiny, are independant and require no more maternal care. Survival in the ocean is often a matter of luck, and very few of these offpspring will survive to adulthood— which is why so many eggs are laid to begin with.