Embryogenesis is the process of embryonic development from fertilization to hatching from the egg.

An embryo is a developing embryo inside an egg. After leaving the egg, the embryo turns into a pre-larva.

Embryonic period - the period of embryonic development from the moment of fertilisation to the beginning of independent functioning of gill, digestive and other systems. The embryonic period is divided into subperiods: a) egg subperiod, when development takes place inside the egg shell; 6) free embryo (prelarva) subperiod, when development takes place outside the egg shell, but free-living individuals that have hatched feed on the yolk.