<i>Macrostomum lignano</i> (IMAGE) Bielefeld University Caption Sperm come in all shapes and sizes: the sperm cell of the flatworm Macrostomum lignano (picture) has a frontal "feeler" (right) and two lateral bristles that may function to anchor the sperm inside the female sperm-receiving organ. Credit Photo: Bielefeld University Usage Restrictions The image may only be used with appropriate caption or credit. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.