Volvox tertius (image) University of Arizona Share Print E-Mail Caption The colonial alga Volvox tertius has about 2,000 cells and a complete division of labor: cells either swim or reproduce, but not both. The few large cells within these colonies are the reproductive cells, while the many tiny cells do the swimming. Credit Copyright 2009 Matthew Herron. Usage Restrictions This photo may only be used to illustrate a story about the research described in the accompanying news release, 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.