Light microscopy of Didinium nasutum reproducing through binary fission. This is an asexual process in which the parent protozoan divides, resulting in two identical daughter cells. This is near the end of the process, just before the two divide. The Paramecium protozoan swimming next to them appears to give them a helping hand by swimming between them to assist in the final separation. The Paramecium is lucky the Didinia are occupied, as Paramecia are their favourite food. Recorded under Nomarski differential interference contrast illumination.