Key events: 1st two nuclear divisions

Stage 1 lasts for about 25 min (0-0:25 h) and begins once the egg has been laid, and ends when the first two cleavage divisions have been completed.


In histological sections, the fertilized egg displays homogeneously distributed yolk granules and egg cytoplasm; only the periphery of the egg, occupied by a thin rim of periplasm, and a cytoplasmic island, located dorsally within the anterior one-third of the egg, which contains the female pronucleus, are yolk free.