Figure 9. The Xenopus Oocyte
The Xenopus oocyte grows in the ovary from a germ cell over many months while it is in first meiotic prophase. When fully grown it can respond to hormones, such as progesterone, to complete first meiosis and arrest in second meiotic metaphase. Once fertilized, it progresses to the blastula stage in 8 hours and somatic lineages already start to appear.