European squid propulsion. The posterior border is slightly concave. The head is relatively small and has large eyes which are covered with a transparent membrane. Like almost all squid, this species has ten limbs surrounding the mouth and beak: eight are relatively short arms, and two, which form the tentacles, are long, as they are used to catch prey. The fourth left arm of males is a hectocotylus. The European squid can grow up to 30–40 cm in the mantle length, but more usually they are 15–25 cm long. The males are generally bigger than the females and exhibit more rapid rates
Spawn (biology) sperm-carrying arm and leave it attached to the female. Deep water squid have the greatest known penis length relative to body size of all mobile animals, second in the entire animal kingdom only to certain sessile barnacles. Penis elongation in the greater hooked squid may result in a penis that is as long as the mantle, head and arms combined. Some species brood their fertilized eggs: female paper nautilus construct shelters for the young, while Gonatiid squid carry a larva-laden membrane from the hooks on their arms. Other cephalopods deposit their young under rocks and aerate them with their tentacles