This is released from the planarian through the mouth. The planarian has a system of tubules extending throughout its body from the anterior to posterior on both sided of the body. These tubules are called protonephridia and they collect both excess water and much of the nitrogen waste. The tubules have pores that lead out of the body. Water and ammonia leaves through these pores.
Aerobic respiration produces carbon dioxide as a waste product.
This is released from the planarian by diffusion. To carry out aerobic respiration, the planarian must get oxygen to the cells of its body. Oxygen enters the planarian by diffusion. The special features of the Phylum Platyhelminthes includes the protonephridia. These structures can be considered primitive kidneys.