Acoelomates: Flatworms
Phylum Platyhelminthes: Flatworms - simple, acoelomate, bilateral animals; definite head and anterior end; possess organs
Solid body except incomplete, branched digestive tract (i.e. only one opening; cannot feed and excrete at same time)
First excretory system: fine tube system throughout body; flame cells with cilia push water and excretory material to pores between epidermal cells (majority of excretion still through gut and mouth)
No circulatory system for oxygen or nutrient transport
Hermaphroditic: contain both male and female gonads