Two Females (IMAGE) University of Michigan Caption Two female bubble-rafting violet snails, Janthina exigua. Scientists believe the bubble float evolved from an ancestral egg mass. Egg capsules are attached to the underside of the floats. Credit Denis Riek Usage Restrictions None 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.