Morphology of <i>in vitro</i> fertilized (IVF) deer mice oocytes at various stages of development <i>in vitro</i>.

<p>Typical phase contrast micrographs of developing embryos derived from IVF of MII oocytes retrieved from superovulation (A-C) and IVM (D-G). Fertilized oocytes with first and secondary polar bodies are clearly visible as indicated by arrows in panels (A) and (D), which was followed by the appearance of two pronuclei (one from oocytes before fertilization and one from sperm) as indicated by arrows in panels (B) and (E) and further development to 2-cell (C and F), and 4-cell (G) stages <i>in vitro</i>. Scale bar: 30 µm.