Abstract
Triclads use the excess of spermatozoa received from the partner during copulation as an additional source of nutritive material. Digestion of sperm takes place in various sperm resorptive organs, such as the copulatory bursa, lateral bursae, spermiduct, resorptive vesicles, and oviducal tubae. Sperm resorptive organs may concern either newly evolved organs, or result from a change of function in an already existing structure.