Fig. 1.

Development of the one-cell C. elegans embryo as viewed by in utero-imaging of a worm expressing GFP::β-tubulin. a Schematic drawing of an adult hermaphrodite. The box depicts the region of the uterus imaged. b Microtubules are observed by fluorescent light microscopy around the oocyte nucleus (t = 0) before it enters the spermatheca (dashed line). Anterior is left in all panels. The oocyte usually enters the spermatheca within 5 min, at which time fertilization occurs and a pointed bipolar array becomes visible. Each round of meiosis takes approximately 20 min. At the end of meiosis II (t = 37:56), the centrosomal microtubules become visible (arrow), and centrosome separation begins soon after. The mitotic spindle forms in the center of the embryo and the spindle skews towards the posterior in anaphase to produce two daughter cells of unequal size. Scale bar is 10 μm in b