To defend themselves a few species have evolved the ability to produce an inky substance that confuses the predator and allows them to escape without a predator seeing them. Other cephalopods have developed the ability to change their skin color to match that of the surrounding territory. They also have a large brain area which gives them high intelligence as well as an advanced nervous system which allows them to outwit the species that hunt them. Behind their head region there is usually a mouth area with 8-10 tentacles extending outward around the opening. These are usually used to collect and bring food to the mouth.
Cephalopods also have anatomy very different from our own.
They have two gills, two kidneys, and three hearts. The nautilus, which is the only cephalopod that has an exterior shell, has four gills and four kidneys. Squid, which is a type of cephalopod, is probably the most common. The squid is long and slender. A pair of small fins called the caudil fins are located above the head.