nematoda
The Nematoda are also known as round worms. It has a digestive system that is broken down into three parts: The Stomodeum, intestine and the proctodeum. The Stomodeum consists of the mouth, lip and esophagus. The intestine is where the food goes when its eaten, and the food is later excreted out the anus.
clam worm
Food enters the mouth or jaws, which are 2 claw liked teeth. It also uses its tentacles to pull food in toward them. Food enters past the mouth, through the esophagus and pharynx into the intestine. Digestive enzymes help to digest food, and the nutrients get absorbed. The waste proceeds through the proctodeum which is then excreted to the anus.
tube worm
Interesting enough, tube worms have no mouth and no digestive system. In fact, the tube worm lives in deep sea climate, with no food and no light to begin photosynthesis. it is a plant like bacteria itself, and it survives using a technique called chemosynthesis. it uses the bacteria surfacing within its hydrothermal vents, and converts it into food for itself.
nematode
If you remember the spongebob episode with the nematodes, you'd know that they ate everything in sight. The nematode has an oral cavity lined with a cuticle, and may bear teeth. The Nematode also has a stylet, which it can stab into its prey. The pharynx connects the mouth to the intestine, because it has no stomach, and thats where digestive enzymes break dan the food. The stylet can also inject digestive enzymes into the prey to liquify it. The food then travels to another hole with a cuticle lining which is the anus.