The older theory is fission, in which the fertilized egg splits partially.

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

The egg split open, and there was a shining stone inside.

The fertilized egg then splits into two or more embryos.

But two eggs split three ways is sort of feeble.

For unknown reasons, the fertilized egg splits into two embryos during the first stage of development.

Abruptly an egg split open, and a moist little brown dragon was spilled to his feet on the hot sands.

The egg will then completely split into two, normally at the two cell stage.

However, the egg can split into two, but still have one blastocyst.

If an egg splits in two after fertilization, identical twins are produced.