Various lines of defense from disease or infection include Leukocytes, the skin, mucous, and interferons.

Its the Tube because there are flame cells which help in excretion and occur in flat worms. The excretory system is unique in round worms which contains canals and tube. Annelids have nephridia as their excretory organ. Arthropods have malphigian tubules as their excretory organ.

The excretory organs found in flatworms and earthworms are called nephridia.

The excretory organs found in flatworms and earthworms are called NEPHRIDIA. It is a waste-discharging tubule with an external excretory pore, found in many invertebrates, as in worms, mollusks, etc.