Earthworm

• The total surface area of the earthworm's skin forms the gaseous exchange surface. Gases move directly through the skin by diffusion
• The earthworm's skin is very thin (thin epidermis) and kept moist by mucus from skin epidermis. and coelomic fluid secreted onto the skin
• O2 diffuses into skin blood vessels, larger blood vessels transport it to the rest of the body. Co2 is transported to the skin in the same way and diffused out the body
• The skin is protected by mucus and coelomic fluid