Cell division in Tetraedron

Abstract

Mitosis and cytokinesis in Tetraedron are described. Persistent centrioles replicate before division and the pairs separate to define the future poles of the spindle whilst increasing numbers of microtubules become associated with them. By prophase, the centrioles and most extranuclear microtubules have become enclosed within a 'perinuclear envelope' of endoplasmic reticulum. The nuclear envelope near the centrioles then becomes indented and finally ruptures to form polar fenestrae during prometaphase; the extranuclear microtubules soon vanish and appear to move through the fenestrae into the forming spindle. Metaphase, anaphase, and telophase follow as usual. After mitosis, arrays of 'phyco..