The Hookworm is a type of roundworm that lives in the small intestines of other animals. They are a parasite and feed of the food that other animals eat by eating it from inside the stomach of their host. They are only about an inch to a half a inch but they can cause you a serious amount of damage if they get into your system. They are like most other members of the worm family because they can get oxygen into their body through diffusion. They have no respiratory organs and their skin is permeable to oxygen.