The nurse cells and the oocyte arise from a common oogonium, which gives rise to one oocyte and 15 nurse cells (only 7 of which are seen in this plane of section). These cells remain joined by cytoplasmic bridges, which result from incomplete cell division. Eventually the nurse cells dump their cytoplasmic contents into the developing oocyte and then kill themselves. The follicle cells develop independently (from mesodermal cells).