Light micrograph of the ciliate protozoan Paramecium sp., undergoing division or binary fission, a type of asexual reproduction. Ciliates possess two different types of nucleus; a small diploid micronucleus & a larger polyploid macronucleus. At least one of each type is normally present in each individual, but in some species there may be several of either or both types. Both types of nucleus divide during binary fission and a copy of each passes to the two genetically identical daughter cells. Magnification: x400 at 35mm size.