1.   In other species, polarization comes a bit later, after the fertilized egg has split a few times into a cluster of identical cells.

2.   In the womb, the egg occasionally splits into two separate embryos that develop as identical twins.

3.   In the Texas armadillo, such an egg always splits into six, producing sextuplets.

4.   When females mate with males, the fertilized egg splits, or clones itself, giving rise asexually to multiple identical offspring.

5.   Genes would be tested after the eggs had split a number of times in the laboratory, and only the healthy ones would be returned to the uterus.

6.   In this case, the fertilized egg split into two embryos, creating twins.