The four nuclei present towards the micropylar end  in an embryosac during its formation contribute in the formation of all expect 

There is a characteristic distribution of the cells within the embryo sac. 

Three cells are grouped together at the micropylar end and constitute the egg apparatus. 

The egg apparatus, in turn, consists of two synergids and one egg cell. 

The synergids have special cellular thickenings at the micropylar tip called filiform apparatus, which play an important role in guiding the pollen tubes into the synergid. 

Three cells are at the chalazal end and are called the antipodals. The large central cell, as mentioned earlier, has two polar nuclei. 

Thus, a typical angiosperm embryo sac, at maturity, though 8-nucleate is 7-celled