SUMMARYThe process of chloroplast division during mitosis inChlamydomonas reinhardiis followed with the electron microscope. The pyrenoid and the chloroplast reproduce by fission. The dividing chloroplast contains regions of dense material that superficially resemble pyrenoids, but it is concluded that the formation of the dense material is not related to pyrenoid formation inC. reinhardi.The dense material appears to be localized over regions of chloroplast DNA.