Final answer:
The development of the secondary oocyte within a vesicular follicle is arrested in metaphase II, and it will only complete meiosis II if it is fertilized.
Step-by-step explanation:
Within a vesicular follicle, the development of the secondary oocyte is arrested in metaphase II. This occurs after the oocyte has completed meiosis I and is poised to complete meiosis II upon fertilization. When the primary oocyte finishes meiosis I, most of the cellular material and organelles are allocated to one cell, the secondary oocyte, while the other cell, called a polar body, typically dies. The secondary oocyte begins meiosis II but is halted at metaphase II and does not proceed unless fertilization occurs, at which point it completes meiosis II, giving rise to the fertilized egg with the proper chromosome number to develop into an embryo.