Complex sentence: Rhombomeres Rh7-Rh4 form the myelencephalon, and rhombomeres Rh3-Rh1 form the metencephalon.
Split into simpler sentences: Rhombomeres Rh7-Rh4 form the myelencephalon. Rhombomeres Rh3-Rh1 form the metencephalon.