| Diploid zygotes created by combining a male and a female pronucleus gave rise to viable embryos, but combining two male or two female pronuclei did not. |
| In fact, occasionally, only one pronucleus is produced, and there is now evidence that suggests, that this pronucleus is diploid. |
| After the encounter of the two pronuclei, one quadrant of the former positive cross of the monaster is missing on the side of the egg pronucleus. |
| After its entry into the egg cytoplasm, the spermatozoal nucleus, now called the male pronucleus, begins to swell, and its chromosomal material disperses and becomes similar in appearance to that of the female pronucleus. |
| Each pronucleus stores the genetic material characteristic of the partner from which it comes, and the combination of these two shall determine the genetic makeup of the new embryo. |
| Before fertilization a type of cell division called a reduction division brings the number of chromosomes in the female pronucleus down to 23, including one X chromosome. |
