Mallard Oviduct and Phallus (IMAGE) Yale University Caption Evolution of convolutions in the Mallard oviduct (below) and phallus (above) may give the female duck an anatomical means of controlling who fathers their offspring. Bar measure = 2cm. Credit Courtesy of Patricia Brennan Usage Restrictions with credit given 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.