Embryos of the Penis Worm (IMAGE) University of Bristol Caption Embryos of the penis worm (Markuelia) from the Cambrian of China and Siberia. Images: a-b: two views of the whole embryo; b-f: successively lower rings of teeth around the mouth; g-j: anus and digestive tract; i-j: spines around the anus. Credit Phil Donoghue Usage Restrictions Only to be used to accompany article about this work. 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.