Flagellar beating in Volvox carteri, as evidenced by the moving of natural particles in the surrounding medium, as well as the moving of added fluorescent particles; the vector field generated by a Particle Image Velocimetry, PIV, software (courtesy of Cristian Solari, John Kessler, and Ray Goldstein, University of Arizona).

Upwards swimming in young (gonidia-containing) and mature (embryo-containing) colonies of Volvox carteri; their sedimentation speed (when deflagellated) is also shown, to indicate differences is swimming capabilities as a function of mass (courtesy of Cristian Solari and John Kessler, U. of Arizona)