Tube Within Tube Body Plan

In the tube within tube body plan, the digestive system is a tube running through the body cavity, with the mouth and anus located at two separate ends. This allows a one-way, continuous passage of food, which is more efficient than the blind sac plan. From Phylum Annelida onward, every phylum studied in this chapter shows this body plan. Annelids such as Nereis, Pheretima (the earthworm) and Hirudinaria (the leech) already show this complete alimentary canal running the length of the segmented …