A Female Sexual Polyp of the Cnidarian Hydractinia Symbiolongicarpus (image) NIH/National Human Genome Research Institute Share Print E-Mail Caption Piwi1-positive oocytes are shown in yellow; cell nuclei are in turquoise. Germ cell induction and all stages of gametogenesis can be visualized in these clonal animals. Credit Timothy DuBuc, Ph.D. Swarthmore College Usage Restrictions Please provide credit to the artist and institution when using the image. This image may only be used with reports of this research. Share Print E-Mail 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.